EMBRYO-TRANSFER TWINNING AND PERFORMANCE EFFICIENCY IN BEEF PRODUCTION'
P. Guerra-Mamnez2, G. E. Dickerson3, G. B. Anderson4 and R. D. Green5 University of Nebraska, Lincoln 68583-0908 and University of California, Davis 95616 ABSTRACT
Effects of twinning on efficiency of beef production were estimated from results of bilateral transfer of two Angus x Hereford (AxH) embryos into each of 241 heifers and 84 cows (H, A, HxA or Holstein x H)over 4 yr. Calves were weaned at 180 d and fed either 220 d in a feedlot (1977) or 170 d on forage and 140 d in a feedlot (1978 to 1980). Effects of parity, twinning and sex of calf were estimated as covariates within year-breed of dam. Pregnancy at 45 to 60 d of gestation was 68% in heifers (H) and 74% in cows (C), with 40% single (S)and 60% twin (T) births. Dystocia was 28% in H vs 10% in C (P e .05), and tended to be less (P > .05) for T than S in H. More placentas were retained (P c .05) for T than for S in both H (35 vs 12%) and C (24 vs 4%). Twin gestations averaged 3 d shorter and subsequent calving intervals 13 d longer (P < .05), but total calf mortality was slightly higher (P > .05). Abortions were 4% in H only. Twinning females lost maternal weight during late gestation (P c .05) when crowding limited voluntary feed intake, while fetal requirements were 60% higher (P c .01). Twins increased milk output 25% (P e .05), but 11%higher feed intake maintained cow weight during lactation. Twinning reduced birth weight 13% and weaning weight 17% (P < .05), but 400-d feedlot weight only 9% because of compensating feedlot gain. Twins gained 18% faster than S during postweaning 17O-d forage feeding, but 5% slower in feedlot to 8% lighter 490-d weight (P e .05). Assuming 40% higher veterinary and labor costs for twins, estimated integrated herd costs per unit of ageconstant output value would be lower for T than for S production by about 24% for marketing either at weaning or at 400 d. (Key Words: Cattle, Multiple Births, Growth, Reproduction, Meat Yield.) J. Anim. Sci. 1990. 68:4039-4050
as Holstein, Brown Swiss, Charolais, Simmental and Maine Anjou (Johansson et al., Twinning is relatively rare in cattle, ranging 1974; Willis and Wilson, 1974; Rutledge from less than 1% in Hereford, Angus and 1975; Reid et al., 1986). Twinning in cattle Zebu breeds to over 3% in some breeds such potentially is important for increasing efficiency of beef production because the overhead costs for maintaining single-calving cows 'Published as Paper No. 9099, Journal Sa.,Nebraska account for over 50% of total costs of beef Agric. Res. Div., Univ. of Nebraska, Lincoln. Partial production (Dickerson, 1970; 1978; 1983). publication from M.S. Thesis of senior author. Twinning could spread these cow costs over 2Present address: IDIAP, Apdo 958, David, Chiriqi, 60 to 70% more calf weight at weaning PaUallla. 'Roman L. Hruska U.S. Meat Anim. Res. Center, (Turman et al., 1971; Vincent and Mills, 1972; ARS, USDA, A218 AnS, Univ. of Nebraska, Lincoln. Bar-Anon and Bowman, 1974; Cunningham, %ept of ~nim.sci.. univ. of california, &vis. 1977; Diskin and Sreenan, 1985). However, b p t . of Anim. Sci., Texas Tech Univ., Lubbock in cattle twinning has been tempered interest 79409-2141 by various degrees of phenotypic association Received December 11, 1989. Accepted May 1, 1990. with shorter gestation, lighter birth and weanlntroductlon
4039
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GUERRA-MARTINEZ ET AL.
TABLE 1. NUMBER OF R Z P I @ N T FJ3MALES ing weights, higher calf mortality, more BY BREED AND YEAR FOR BILATERAL retained placentas and the possibility of TRANSFER OF ANGUS X HEWFORD delayed rebreeding under management inEMBRYOS 5 DAYS AFTER ESTRUS tended for single calvings (Erb and Morrison, 1959; Hendy and Bowman, 1970; Wyatt et al., Year Breed Heifers Cows Total 1977; Larson et al., 1985; Guerra-Martinez, 1977 Herefordo 38 37 75 1986). Such limitations on gains from twin- 1978 Hereford 18 13 31 ning may be less important under nutrition and Angus (A) 15 16 31 management appropriate for twin-bearing 34 HxA 16 18 cows, especially in populations selected for 49 47 96 genetic ability to consistently produce and rear 1979 Hereford 31 31 twin calves (Maijala and Osva, 1988). The Angus 26 26 26 26 present study is an experimental evaluation of HxA 83 83 the effects of embryo transfer twinning on performance of cow and calf and on estimated 1980 Hereford 36 36 35 HolsteinxH 35 net costs per unit of beef output value. Experimental Procedure
Data from a 4-yr superovulation and embryo-transfer experiment conducted at the University of California-Davis (Anderson et al., 1979; 1982) were analyzed to evaluate changes in performance, in outputs and in costs from twin calvings of cows that normally would produce single calves. Earlier publications reported part of the results for effects on reproduction (Wheeler et al., 1982), maternal energy requirements (Koong et al., 1982) and feedlot performance (Garrett et al., 1982). Management. For calving in 1977, 38 Hereford (H) heifers and 37 H cows were artificially inseminated with semen fiom a Red Angus (A) bull followed by unilateral transfer 5 d after estrus of one AxH embryo into the uterine horn opposite to the corpus luteum pable 1). For calving in 1978 through 1980, one AxH crossbred embryo was transferred by midventral laparotomy into each uterine horn of a synchronized recipient female (Anderson et al., 1982). Cows and heifers of the same breed were compared only in 1977 and 1978. Heifers and cows used in 1978 were H, A and HxA. Only H, A and HxA heifers were used again in 1979 and H plus Holstein x H heifers were used in 1980. Pregnancy and number of fetuses were determined by palpation per rectum at 42 to 48 d of gestation and again at 180 to 200 d. In 1977, pregnant recipients were fed primarily chopped oat hay until changing to 50% chopped oat hay and 50% chopped alfalfa hay during the last trimester and during lactation. Both diets contained about 1.8 McaVkg DM (Garrett et al., 1982). Calves in 1977 had
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Totals
71 241
84
71 325
access to the diet of the dam and to a pelleted creep feed. In the latter 3 yr, pregnant and lactating females and their calves had ad libitum access to a diet containing 61% oat hay, 36% rolled barley, 2% cottonseed meal, .7% oyster shell and .5% trace mineralized salt; this diet contained about 2.3 McaVkg DM. No other creep feed was supplied. Each cow and her calf or calves was confined to a single pen during the suckling period. Females were observed closely at calving; deliveries that were assisted because of either large size or malposition of the calf were classified as dystocia. Ages at calving were 24 to 36 mo for heifers and 3 to 12 yr for cows. Calvings were 29% in July, 45% in August, 9% in September, 12% in October and the remaining 5% in May, June and November. Following calving, females were exposed to H bulls from 45 d postpartum until pregnancy was confirmed by palpation. Postpartum days to first ovulation and to next calving were recorded only for 1977 calvings and days open for 1977 and 1978 calvings, using weekly plasma progesterone assay to predict day of ovulation and palpation on d 42 to 48 to predict conception (Wheeler et al., 1982). Cow Weights. Females calving in 1977 were weighed each week during gestation; those calving in 1978 and 1979 were weighed at 3- to 4-wkintervals, and those in 1980 were not weighed. Because cow weights 24 h postcalving varied greatly, change in body weight during gestation (CBW) was estimated (Koong et al., 1982) as follows:
TWINNING AND EFFICIENCY OF BEEF PRODUCTION
CBW = (precalvingweight - 1.5 x calf birth weight) - initial weight (1) Both precalving and initial (WTIG) weights were calculated from within cow linear regression, using all interval weights. Gestation average daily gain (GDG) was calculated as CBW/gestation length in days, and postcalving weight (WTCAL) was estimated as follows: WTCAL = (GDGx280)+WTIG.
(2)
Cows were weighed each week during lactation in 1977 and at 3- to 4-wk intervals in 1978 through 1980. Cow weights at weaning (CWTW) were used to calculate lactation daily gain in weight (LDG), using calf age in days at weaning (AWN), as follows:
and adjusted cow weight at 180 d weaning as follows: A
m = (LDGx 180) + WTCAL.
(4)
Calf Weights. Individual calf weaning full weights (WWTC) at 170 to 190 d of age and birth weights (BWTC) were used to calculate preweaning daily gain, WDG = (WWTC-BWTC)/AWN
(5)
and adjusted 180-d calf weaning weight, AWWTC = (WDG x 180) + BWTC.
(6)
Relative preweaning percentage growth rate (WRG) of calf was calculated as follows: WRG = 200PWDG/(AWWTC BWTC).
+ (7)
Similarly, the adjusted slaughter weight (ASWTC) and percentage relative postweaning growth rate (PRGC) were calculated from postweaning daily gain (PDG), full weight at slaughter (SWTC), and age at slaughter (AS) and weaning (AWN) as follows: PDG = (SWTC- WWTC)/(AS - AWN) (8) ASWTC = (PDGx220)+AWWTC,and (9)
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PRGC = 200PDG/(ASWTC + AWWTC).
4041 (10)
For postweaning backgrounding periods on forage and for the subsequent feedlot periods in 1978 through 1980, body weight and relative growth were adjusted to 170 d and 140 d, respectively, as described above for the postweaning feedlot period. Milk Production. In 1977 through 1979, milk production was estimated by the weighsuckle-weigh method. Calves were separated from d a m s from 0600 to 1200, weighed, allowed 45 min to suckle and reweighed. The gain in calf weight multiplied by 4 was the estimated 24 h milk production. Measurements were taken weekly in 1977 from calf ages of about 15 to 121 d, but at 2 8 d intervals from calf ages of 40 d in 1978 or 28 d in 1979, until 170 to 180 d. The method of Jenkins and Ferrell (1984) was used to estimate total 18Od lactation milk yield (TMY), day of peak milk yield (TPY), peak daily milk yield (PMY) and persistency (PER = TMY/PMY). Feed Consumption and Energy Requirements. Individual cow feed consumption (MEI) was recorded weekly only in 1977, from conception to weaning of calves. Metabolizable energy requirements for pregnancy (MEP) were estimated individually from net energy gain of the conceptus adjusted for calf birth weights; those for change in cow body energy content and for maintenance (MEM) were predicted from changes in cow weight (Koong et al., 1982). The energy requirements for milk production (MEL) assumed that milk composition was 3.2% fat, 3.1% protein and 4.4% lactose, with gross energies of 9.4, 5.8 and 4.4 kcal/g, respectively, and that efficiency of ME use was 63% for milk secretion. These calculate to 1.07 Mcal ME required/kg milk produced. The MEM during pregnancy and lactation were obtained by difference by subtracting ME for changes in cow body weight and either MEP or MEL from total MEI, where MEI(Mcal/d) = 1.8 kg x DMI. In 1977, calves weaned at about 6 mo of age were fed individually a blended diet containing about 2.58 Mcal MEkg dry matter. Male calves had been castrated at about 4 mo of age. Steers were implanted with Synovex-S after about 50 d on feed. Calves were slaughtered at a typical low Choice visual grade (Garrett et al., 1982). Daily feed consumption was computed from total feed
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GUERRA-MARTJNEZ ET AL.
TABLE 2. SIMPLE MEANS FOR PREGNANCY AND CALVING RATES PLUS EMBRYO AND CALF SURVIVAL FROM BILATERAL EMBRYO TRANSFERS Heifers
Traits
No.of recipient females No.pregnant at 45 to 60 d %'
No.calved %'
No. with dystocia %b
No.with retained placenla %b
No.of fetuses Abmtiom, %' Other fetal loss, %' No.of calves born stillborn,%d Early mortality. %* Total lost fetuses, abc No.at 1 wk
Single
Twin
66 27.4 59 24.5 22 37.3 7 11.9 66 3.O
98 40.7 88 36.5 19 21.6 31 35.2+ 1% 4.1
59 3.4 8.5
176 7.9 11.9
52
141
COWS
All
%f all recipient females. Some dams with twins lost one em%f all females calving in each parity and type of birth.
241 164 68.1 147 61 .O 41 27.9* 38 25.8* 262 3.8 6.5 235 6.8 11.1 26.3 193
Single
Twin
All
15 17.9 23 27.4 2 8.7
47 55.9 37
62 73.8 60 71.4 6 10.0 10 16.7 109 0 11.0 97 6.2 9.3 24.8 82
84
1 4.3 15 0
44.0 4 10.8 9 24.3*
94 0
23 8.7 4.3
74 5.4 10.8
20
62
after 60 d.
'Of total fetuses at 45 to 60 d in each parity.
'bf all
calves born for each parity and type of birth.
+P < .05.
(as-is) intake (TF,kg) and days on feed (DF); feed conversion ratio (FRC) was calculated from TF and weight gain (G, kg) on feed as TF/G. Proportion of observed intake utilized for maintenance (MEM) vs gain (MEG) was estimated from partial regression on mean metabolic size (W75) and G (van der Merwe and Rooyen, 1979). In 1978 through 1980, weaned calves were reared on forage without recording feed intake for 145 to 230 d; calves then were fed individually for 127 to 153 d. Records were adjusted by covariance to 170 d on forage and to 140 d in feedlot. Feedlot records for 1978 through 1980 were utilized as described above for 1977 data. Statistical Analyses. Heifer vs cow contrasts were balanced within year and breed of recipients for 1977 and 1978, but only heifers were used in 1979 and 1980 (Table 1). Single vs twin contrasts occurred with variable frequencies within year-parity subclasses, as did male vs female contrasts within yearparity-twinning subclasses. Therefore, a sequential analysis of variance (Type I SS) was utilized to estimate effects of parity (P), twinning (T)and sex (S) of calf as covariates, after fitting the fixed effects of year and breed (B) of recipient (Freud and Littell, 1981). All two-, three- and four-way interactions were
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examined and the nonsignificant ones were excluded from the final models, using residual error for tests of significance. Results and Discussion
Reproduction and Lactation. Simple mean pregnancy rates for cows vs heifers were 74 vs 68% at 45 to 60 d of gestation and 71 vs 61% at calving, with a higher proportion of twin pregnancies for cows (76 vs 60%) at 45 to 60 d but not at calving (62 vs 60%, Table 2). Dystocia was more common for heifers than for cows (28 vs 10%.P < .05) and was slightly more common (P > .05) for heifers with twin than with single calves (37 vs 22%). For single calves, dystocia was primarily due to the large calf size relative to pelvic area (Price and Wiltbank, 1978), but for twins assistance was for repositioning one or both calves to facilitate delivery. Voluminous literature reports are inconclusive concerning the effect of twinning on dystocia (Guerra-Martinez, 1986), perhaps because of different definitions of dystocia. Retained placentas were more frequent (P < .OS) for heifers than for cows (26 vs 17%),and also for twins than singles (P < .05) in both heifers (35 vs 12%) and cows (24 vs 4%).
4043
TWINNING AND EFFICIENCY OF BEEF PRODUCTION
TABLE 3. LEAST SQUAREs MEANS FOR TWIN (T) VS SINGLE (S) CALVING OF HEIFERS AND cowsa
cows
Heifers
S
Traits
Gestation period, 280 d Wt at conception, kep Gestationwtgain, db Wt after calving, kggb Gestation length, da Last trimester, 95.dc Change in maternal body wt, g/d MEI, i n t a k e b ~ gk~W ~, d MEM, maintenance/k 75, k W d MEP,pregnancyBg 7! kcUd
TIS, %
T
351.6 290 432.4 276
335.7 330 428.1 280 5 187 144 44
-356 176 137 64
105 88"
101 98.6; -7,120+ 94 95* 153;;
TIS, 96
T
S
403.5 240 470.1 280
90 179 135 38
454.4 160 497.9 278 -568 170 159 64
113 67; 106 99.0* -631. 95 118* 170+*
(MEM+MEP)
MEI
/kg7',kCaUd
Lactation, 180 da Wt gain, g/d Wt at weaning, k Mid-lactation,Wg.. kg MEI,intake/kg'15, kcad' MEM, maintenance g75, kcad' MEL.lactatioqkg7/: kcal/dc
m&m)m75, kWdC Total 180-d milk yield, kgb Peak milk yield, kg/db Persistency, totaVpeakb Calving to 1st ovulation, dC Calving to conception, dd - interval, dc Calving
bats from bData from 'Data from %ata from
1.14
114
460 520.8 101.7 289 193 71
480 526.7 102.5 307 193 87
104 101 101 106* 100 123
360 546.3 107.0 264 196 57
.91 1,233 8.8 132 50 68 356
.91 1.5% 11.4 133 68 87 364
100 129 13P 101 134* 128 102
1,075 8.1 128 62 88 368
1 .00
.97
.%
1.31 380 5702
134 105
308 200 85
104 104 117* 102 149;
.93 1,305 9.3 123 70 86 387
96 121 115. 96* 113* 98 105*
111.1
1977 through 1980, except as noted. 159 female calvings in 1977 through 1979, for body weight excluding uterine content. 56 females calving in 1977 when diet during last himester contained 1.8 Mcal m/kgDM. 83 females calving in 1977 and 1978. all females calving,
*P < .05. **P < .01.
These results are in general agreement with the literature (Vincent and Mills, 1971; Diskin and Sreenan, 1985; Guerra-Martinez, 1986). First postpartum ovulation following twin births in 1977 data (Table 3) was delayed (P e .01) in both heifers (68 vs 50 d) and cows (70 vs 62 d); the corresponding differences (P e .05) in the subsequent calving interval were 8 and 19 d. However, in the combined 1977 and 1978 data, the corresponding differences in days open were nonsignificant (19 and -2 d), perhaps because energy density of the diet fed during the last trimester of pregnancy was increased from 1.8 to 2.3 Mcal ME/kg DM in 1978. Gestation length was 3 or 4 shorter (P < .01) for twin-bearing cows or heifers; this makes the calving interval shorter but makes subsequent days open and calving intervals
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longer, especially when associated with retained placentas. Most of the literature concerning effects of twinning on reproduction are for dairy cattle (reviews by Hendy and Bowman, 1970; Bu-Anon and Bowman, 1974; Syrstad, 1977; Chapin and Van Vleck, 1980) and clearly demonstrate longer days open and calving intervals following twin biahs. Wyatt et al. (1977) also observed that adoption of a second newborn calf at parturition delayed postpartum ovulation in Hereford x Holstein crossbred cows. Females producing twins in 1977 to 1979 were somewhat heavier (P > .05) than single calvers at conception (Table 3), but their weight gain during gestation was 12% less in heifers and 33% less in cows (P e .05), so that weight after calving was only slightly above
4044
GUERRA-MARTINEZ ET AL.
that of single calvers. Energy content of the diet was about 1.8 Mcavkg DM in 1977 and 2.3 Mcavkg DM in 1978 and 1979. During the last 9 5 d trimester for 1977 data, the carrying of twin fetuses caused losses in maternal body weight of 34 kg in heifers and 54 kg in cows, compared with gains of .5 and 8.5 kg, respectively, for single calvers (P < .05). Energy intake in 1977 was 5 or 6% less for twinning females, presumably because abdominal crowding limited physical capacity. Calculated requirements for pregnancy were higher for those carrying twins in both heifers (53%) and cows (70%); hence, energy requirements exceeded energy intake in 1977 by 14 and 34%, respectively. The earlier report on the 1977 part of this experiment by Koong et al. (1982) concluded that a higherenergy diet would be required both to prevent loss of weight by beef cows carrying twins and perhaps to reduce the incidence of delayed rebreeding following twin births. During lactation in 1977, voluntary feed energy intake per kg.75 of body weight was higher (P c .05) for twinners by 6% in heifers and by 17% in cows (Table 3), thus meeting the 23 and 49% higher energy requirements
associated with 29 and 21% greater (P < .05) estimated milk production, and allowing slightly greater (P > .05) gains in weight for twinners of 4%in heifers and 5 % in cows. The estimated energy required for maintenance was higher during lactation than during late gestation (196 vs 145 K c a U l ~ gx. ~d-l); ~ both were somewhat higher than reported by Ferrell and Jenkins (1985) for beef cows. However, estimated maintenance requirements were no higher for the cows nursing twins. Effects of twin calves on milk production are different for suckler beef production than for dairy cows, because milk output is limited by milk demands of the calves, which are greater for twins. Studies with dairy cattle (Syrstad, 1977) have indicated that milk production increases after cows produce twins but is lower for cows carrying twin calves. The low energy content of the 1977 diet could have limited milk yield by dams nursing twin calves. Calf Performance. Abortions were rare and occurred only in heifers (4%; Table 2). Of all fetuses counted at 45 to 60 d gestation, 10 to 11% were lost before birth by either absorption or abortion, and another 14 to 16% died at birth or before 1 wk of age. Calf mortality
TABLE 4. LEAST SQUARE!S MEANS FOR ' I "(T) AND SINGLE (S) INDIVIDUAL CALWS FROM HEIFERS AND COWS, BY SEX OF steers Traits
Dam
Wt at birth, kg
Heifer cow
Reweaning 180 d Wt gain, W d Relative growth, %/d 18bd wt, kg
Heifer cow Heifer cow Heifer
cow
T
S 34.0 31.6 37 .95 .77
.a2 190.7 206.0
27.7 29.8 .71 .79 .75 .77 157.1 172.4
Heifers
TIS,% 82,
94, 82* a3* 97
94 a2*
u*
s
T
26.7 33.7 .83
.91 .82 .79 181.7 197.0
TIS,%
Au TIS,%
23.6 28.8
a8* a3*
a5* a9*
.67 .75 .77 .79 148.1 163.4
ai* 82. 94
ai*
loo a2*
a3*
a3* 96
97
a2* a3*
Postweaning 220 db 206.5 155.2 75* 181.3 150.6 Initialwt,kg 1.27 121 95 1.03 1.09 Wt gain, W d A1 111* .37 .39 Relative growth, %/d .35 6.4 6.2 97 6.7 6.3 FWgain. kg DM/kg 485.9 421.4 a7* 407.9 390.5 W d w, kg 346 290 84* 295 270 Mid wt, kg F e e d i n t i ~ k e ~kcad ~* 259 278 107* 265 268 Maintenance&'5, kcdd 1 a0 174 97 la3 iai Maintenancefitake. % 69.5 62.6 90, 69.0 67.5 -or 272 calves from yr 1977 through 1980, except that postweaning feedlot data were for only bAssuming 2.58 Mcavkg dry matter intake (Garrett et al., 1982). Data b o r n 1977 only.
*P < .05.
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a3* 106 111*
94 %*
92 1.01
79* 100 111 95 91
aa* 104
98 98 94* 60 calves in 1977.
99
4045
" N I N G AND EPPICIENCY OF BEEF PRODUCTION TABLE 5. LEAST SQUARES MEANS FOR POSTWEANING PERFORMANCE OF 134 TWIN 0 AND 73 SINGLE (S) CALVES DURING BACKGROUNDING (180 TO 350 DAYS) AND FEDLOT (350 TO 490 DAYS) PERIODS IN 1978 TO 1980 Steers
S
Trait 180 to 350 d Gain, IEB G d d ,g Relative growth, %/d 350-M kg 350 to 490 d Gain, kg Gain/d, g Relative growth, %id 4 W d wt, kg Mid wt. kg Feed/gain, kg DM/kg Feed intake/kg h a d a MaintenancenEgY5,kcaVdb Maintenance/intake, %
''
T 51.6 303 .136 248
220 1,575 ,423 457 349 5.94 293 20 1 68.6
Heifers TIS. %
60.9 358 .187 224
118. 118* 138* 91*
209 1,495 .433 420 315 5.70 293 201 68.6
95* 9 s 1m* 92* 90 97* 100 loo* 100
S
T 51.0 300 .I45 233
205 1,465 .411 427 323 6.11 2% 201 67.9
TIS. % 60.3 355 .196 210
118. 118* 135*
194 1,385 .421 390 292 5.94 295 201 68.1
95* 95* 1U2* 91* 90 97* 100 100
w
100
'Assuming 2.58 M M g dry matter in diet (Garrett et al., 1982). % s e d on partial regression within breed-year-sex-twinning classes of ME intake on W75and daily gain. *P < .05.
from birth to 1 wk was only slightly higher (P > .05) in twins than in singles from the 147 heifers (20 vs 12%) and 60 cows (16 vs 13%) calving. In numerous studies of calf mortality in dairy cattle (reviews by Erb and Morrison, 1959; Bar-Anon and Bowman, 1974; Johansson et al., 1974), mortality of twin calves was several times higher than for singlebom calves, especially in males. Twin calves were lighter at birth (P c .05) by 15% from heifers and by 11% from cows (Table 4). heweaning gain also was less (P < .05) for twins than for singles by 19% from heifers and by 17% from cows. heweaning weight gain relative to size (%) was only 3 or 4% slower for twins, but weight at 180 d weaning was 16 to 18% lower for twins in both sexes and both parities (P c .05). Studies of twinning from hormoneinduced multipleovulation (Turman et al., 1971; Vincent and Milk, 1972; Bellows et al., 1974) all have reported about 25% lower birth weight for twin- vs single-born calves. Weaning weights of twins with access to creep feed (Turman et al., 1971; Diskin and Sreenan, 1985) were only 14 to 18% below weights of singles, but when creep feed was not available (Vincent and Mill, 1972), twins were 26% below singles in weaning weight. Thus, under creep feeding and ignoring differences in calf crop reared, cows with twins would produce 65 to 70% more weight of calves weaned.
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During the 220-d feedlot period for 1977 calves (Table 4), weight gain of twins vs singles was 5% slower for steers and 6% faster than for heifers, but in both sexes, gain relative to size was 11% faster for twins (P c .OS), because initial weights in feedlot were less for twins than for singles by 24% in males and 16% in females. Thus, the 4OOd slaughter weight was less for twins than for singles by 13% in steer calves and by only 4% in heifer calves (P c .05). Feedgain ratio was only slightly (P > .05)lower (-5%) for twins than for singles. Feed energy intake was 7% higher for twin than for single steers (P c .05) but only 1% higher for twin females. Estimated maintenance requirements per weight75 (van der Merwe and Rooyen, 1979) were only slightly lower for twins of either sex, as reported by Garrett et al. (1982). Thus, the maintenance proportion of total energy intake was less (P < .05) for twins than for singles in steers because of their 16% lower mean weight. During the postweaning 145 to 230 d backgrounding period on forage for the calves in 1978 to 1980, both steer and heifer twins gained 18% faster than singles (P< .05, Table 5). Relative growth rate was faster for twins by 38% in steers and 35% in heifers, so that adjusted 350d weight was less for twins by only 9% in steers and 10% in heifers (Pc .05).
4046
GUERRA-MARTINEZ ET AL.
During the following 127 to 153 d in feedlot, the sets of twins in 1978 to 1980 gained 5% slower than singles in both steers and heifers (P e .05). However, relative growth rate was 2% faster for twins than for singles in both sexes (P < .05) because initial weights were 9 or 10% lower for twins. Both voluntary feed consumption and estimated maintenance requirements per kilogram body weight75 were similar for twins and singles of both sexes, but weight maintained was 10% lower for twins. Although the maintenance propodon of total feed intake was 68 or 69% for twins and singles of both sexes, maintenance was reduced more than gains in twins, leading to 3% lower feed/gain for twins. Total ageconstant 490-d slaughter weight output per female producing twins that survived to market age would be about 83% greater than for females marketing singles. Or course, the higher mortality of twin calves and the greater mortality or culling of twinning cows would reduce the advantages of twinning. However, the freemartin heifers born twin with a male would increase market output, in addition to those from the female twin sets in excess of replacements needed, so that the proportional increase in output above replacement needs would be greater than for total calves reared. Also, feeding twin calves to the same final weight would increase output relative to cow overhead even more. As in the present study, Turman et al. (1971) and Davis (1989) found that twin calves creep-fed to weaning gained about as rapidly as singles in the feedlot, and more rapidly relative to weight maintained (Table 4). Thus, only the disadvantage in weaning weight remained at an ageconstant feedlot endpoint; feedlot gain for twins would be at least as efficient as that for singleborn calves. Similarly, both Kay et al., (1976) and Diskin and Sreenan (1985) found that twin-born calves closely approached the weight of singleborn calves (96 or 98%) at the end of an a g e constant postweaning feeding period. InputlOutput Eficiency. A specific example of input costs and output value is presented here to illustrate potential economic gains from a high frequency of genetic twinning in beef cattle under midwestern U.S.cowcalf-feedlot conditions. The performance data used were for twinning obtained from embryo transfer to females of breeds that normally produce single calves. Also, the fact that these twin-bearing
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heifers and cows in 1977 data lost 34 and 54 kg, respectively, of empty body weight during the last trimester suggests that improved nutrition in late gestation could reduce some of the adverse effects on reproduction and mortality. Further, the estimated non-feed costs per cow for veterinary care and labor were assumed to be 40% higher for twin than for single calvings. Such calculated economic gain from twin calf production should be a conservative estimate of the potential gain from using cattle genetically selected for consistent twin calf production. Estimated input costs for feed, veterinary labor and overhead by segments of the year and for rearing replacements from weaning to breeding age are shown for heifers and cows
TAB= 6. ESTIMATED INPUT COSTS ($) PER HEIFER (H) AND COW (C) CALVING FOR SINGLE (S) AND TWIN CALF PRODUCTION^
0
H Periodhem
S
C
T
S
T
Lactalion (180 d) 146.42
Feed8 otherb
156.41
141.03
169.62
81.19 108.81 81.10 109.36 -
Subtotal 227.61 265.22 221.13 278.98 Second trimester (90d) Feed8 22.95 22.14 24.57 23.76 25.14 33.73 25.38 34.47 otherb Subtotal 48.09 55.87 49.95 58.23 Third trimester (95 d) Feed8 39.99 39.11 40.74 42.20 38.65 52.42 38.17 51.% otherb -
--
--
Subtotal Replacements'
Feed
78.64
91.53
78.91
94.16
35.77
38.52
40.35
44.02
65.03
70.03
73.37
80.04
29.26 31.51 33.02 36.02 -
Other subtotal
~~~
%at
a-
~
or oat-alfalfa hay @ &/kg, salt + minerals @ &/
'Costs during 2nd and 3rd himester and 180-d lactation, respectively, for single births were $2.25. 4.00 and
5.50 for veterinary and medicine and $15.00, $27.50 and $55.00 for labor, but were 40% higher for twin births. These costs were about 5% higher during 2nd trimester when open cows held for culling overlap &eir replacements. Overhead costs added = 10% of all feed and cash costs. cAssUming replacement rates of 19.5, 21.0, 22.0 and 24.046 for HS,HT,CS and Cr,respectively, and $333.50 cost from weaning to breeding for each replacement f s male (Nebr. Coop. Ext. Sen., 1984).
4047
" N L N G AND EFFICl€?NCY OF BEEF PRODUCTION TABLE 7. PREDICITD I " U T / O W U T ($/KG) PER COW CALVING FOR HEIFERS, COWS AND HERD PRODUCING SINGLE VS TWIN CALVES MARKETED AT WEANING Heifers
COW
Herda
Twin/ Twill
Single
Total input, $ Feed Other
174.24 226.47 177.67 231.81 176.94 230.57 -
Total Total output,kg weaned catf-salesb Cull cows equiv' Total
245.13 419.37 128.8 59.2 188.0
$Cos@ output Feed Other Total
Single
256.18
246.69
482.65
279.60
424.36
213.4 63.3 -
Twin
511.41
132.0
242.2
71 .O -
276.7
203.0
79.7 321.9
Single
single, %
Item
Twin
246.36
274.14
423.30
504.71
119%
131.3
235.5 75.9
179% 111%
311.4
156%
68.5 199.8 1.23
.88
.89 .74 - - - 2.22
1.74
2.08
111% 130%
159
2.12
1.62
71% 83% 76%
%sed on replacement female rates of single and twincalving heifers and cows of 19.5, 21.0, 22.0 and 24.0% respectively, including COW mortality of 2% for single and 2.5% for twin calvers, with heifer/cow ratios of .272 for singles and .302 for twinning herds. %sed on mortality for single vs twin calves of 11.8 vs 19.9% from heifers and 13.0 vs 162 from cows, e.g., .441 (190.7) + ( 4 1 - .195) (181.7) = 128.8 kg for heiiers with singles. cCull cows valued at 65% of $134.39/100 kg of live weight for weaned calves (VSDA, 1983), e&, (.195 - .MO) (520.8) (.65) = 59.2 kg for heifers with singles.
rearing single and twin calves in Table 6. Rates of ME i n t a k e / ~ t were . ~ ~ based on 1977 data but applied to weights maintained by single and twin calvers in 1977 through 1980 data, by periods. Other cost figures were from the Nebraska Cooperative Extension Service (1984). Relative prices of inputs and outputs remain reasonably stable even though prices change over time. These costs then were
combined with expected market output of weaned calves and cull cows, in terms of weaned calf equivalent value, for herds producing only single or only twin calves (Table 7). F'roportion of firstcalf heifers was higher for the twinning herd (23 vs 21%) because of slightly higher mortality and culling of cows. Estimated costs for the twinning herd were higher by 11% for feed, 30% for other and
TABLE 8. PREDICTED 220-DAY FEEDLOT INPUT/OWUT FER WEANED SINGLE AND TWIN CALF MARKETED
cow
Heifer Item Total inputs $ Feeda otherb 13% Price lossC Total costs output Feedlot gain cosvkg feedlot gain $
Single
Twin
44.34
32.64
26.75
35.32
29.43
185.34
167.98
182.94
179.07
238.9
23 1.2
235.4
241.1
.727
102.70 44.92
Twin
107.32 45.38
,776
96.89
Single
.777
104.54 45.10
.743
%$/Kg for feed, 3$/rcp for salt/mineral. Equal numbers of steers and heifers.
bveterinary medicine $4.00,labor $27.50, plus 10% of feed and other costs (Nebr. Coop. Ext. Sew., 1984). 'Assuming prices per 100 kg of $134.39 for weaned calves and $116.86 for W d slaughter animals and no mortality (USDA, 1983).
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4048
GUERRA-MARTINEZ ET AL.
19%in total. Weaned calf sales for twins were 79% greater, partly because of the smaller proportion of the female calves required as replacements (i.e., approximately 28% vs 50%, allowing marketing of all of the expected freemartin heifers; 50% of heifers born), compared with a single calving herd. Cull cows marketed would increase only 11% for the twinning herd. Estimated costs per unit output of weaned calf equivalent would be reduced by 29% for feed, 17% for other costs and 24% in total. Feedlot inputloutput economic efficiency for the single and twin steer and heifer calves weaned in 1977 is illustrated for one set of 1984 input prices in Table 8. The difference in price between slaughter weight at 400 d and weaned calves at 180 d ($116.86 vs $134.34/ 100 kg live weight) for the same time period is part of the input cost for weight gained in the feedlot operation. Cost per unit of feedlot gain marketed at 400 d of age would be higher for single than for twin calves (78 vs 73$/kg) because of the 11% faster relative growth rate of twin calves and consequent 5% lower proportion of feed intake required for maintenance (Table 4). However, when fed to the same market weight as singles (10% higher, Table 4), twins would lose part of their advantage in compensatory gain. In an integrated cowcalf-feedlot operation, survival of all single and twin steer and heifer calves born from first and later parities placed in feedlot would be similar to those for calves marketed at weaning (Table 7), about 87% for singles vs 82% for twins. This difference in mortality and in the proportion of heifer calves weaned that were available for feedlot marketing (44/87 vs 59/82) determine the fraction of feedlot costs and outputs/calf (Table 8) represented in the summary of integrated input/ output per cow calving (Table 9). Cow herd costs and weaned calf outputs are from those shown in Table 7. Calf feedlot costs per cow calving are higher for twins by 103% in feed and by 110% in other items, because of the smaller proportion of female calves needed as replacements and despite the higher mortality of twins. Slaughter calf output at 400 d of age also is 96% higher for twins for some of the same reasons. Thus, calculated total costs are 36% higher but total slaughter calf equivalent output value is 79% higher and total input/ output is 24% lower for cows producing twin calves. The reduction is 26% in feed costs, but
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TABLE 9. SUMMARY OF PREDICTED INPUT1 OUTPUT PER COW CALVING FOR INTEGRATED COW-CALP-PEEDLOT PRODUCTION OF SINGLES VS TWIN C A L W MARKETED AT 400 DAYS OF AGE Single Inputs, $ Feed Cowherd Feedlot Total
246.36
Twin
TIS,480
274.14
111
70.15 142.32 - 203 316.51
416.46
132
176.94
230.57
130
2M.10 523.61
293.76 710.22
142 136
302.8
594.6
1%
Other
Cowherd Feedlot Total Total output, kga W d slau. wt cullcow equiv. Total Inputkg output, $ Feed 0thTotal
30.16 63.19 - 210
79.0 87.6 111 381.8 .83
682.2 .61
.54 - .43 -
1.37
1.04
179 74 80 76
Y u U cows valued at 75% of slaughter calf price.
Mortality 13% for single and 18% for twin calves.
only 20% in other costs, largely because 40%
higher cowherd costs for labor and other nonfeed items were assumed for cows producing twins (Table 6). If twin and single calves are marketed at the same weight rather than at the same age, the reduction in cow overhead costs per kilogram of output combined with some increase in feedlot costs for twins would be expected to lower costs/output even more than 24%. The primary reason for interest in twin beef calf production is the potential reduction of one-fourth or more in cost per unit of market value from spreading cow herd costs over greatly increased output. Relative potential for improved efficiency from twincalf production is much less when the major output is milk for human consumption. Historically, selection has not favored twinning, mainly because the handicap in calf birth weight, viability, and preweaning growth has discouraged use of twin-born sires, especially under more traditional extensive systems of production. However, the increased efficiency of beef production from twinning is substantial even under the moderate nutritional environments reported here, and can be increased further by strategic
TWINNING AND EFmcTwcy OF BEEP PRODUCTION
4049
Friesian d a q herds. Anim. Prod. 18:109. Bellows, R. A,, R. E. Short, J. J. Urich and 0. F. Pannish. 1974. Effects of early weaning on post-partum reproductionand growth of calves born as multiples or singles. J. Anim. Sci. 39:589. Chapin, C. A. and L. D. Van Vleck. 1980. Effects of twinning on lactation and days open in Holsteins. J. Dairy Sci. 63:1887. cunningham, E. P. 1977. ZUchterisch konsequenzen dor aonwendung n d e r biolichnischen verfahren beim Rind. Zuechtungskunde 49449. Davis, M. E. 1989. Use of embryo transfer to produce twinning in beef cattle: postweaning performance of calves. Livest. Prod. Sci. 23:295. Dickerson, G. E. 1970. Efficiency of animal productionmolding the biological components. J. Anim. Sci. 30 849. Dickerson, G. E. 1978. Animal size and efficiency-basic concepts. Anim. Prod. 27367. Dickerson, G. E. 1983. Potential genetic improvements in the efficiency of beef production. In. Y.Yamada (Ed.) Strategies for Efficient Beef Production, Proc. Int. Symp. on Beef Prod. pp 85-119. Kyoto, Japan. Diskin, M.G. and J. M. Sreenan. 1985. Production and management aspects of single and twin-bearing beef cows. Anim. Prod. 40:533 (Abstr.). Echternkamp, S. E., K. E. Gregory, G. E. Dickerson, L. V. Cudiff, R M. Koch and L. D. Van Vleck. 1990. Twinning in cattle: U. Genetic and environmental effects on ovulation rate in puberal heifers and postpartum cows and the effects of ovulation rate on embryonic m i v a l . J. Anim. Sci. 68:1877. Erb, R. E. and R. A. Morrison. 1959. Effects of twinnin8 on Implications reproductive efficiency in a Holstein-Fresh herd. I. Dairy Sci. 42512. Transfer of Hereford x Angus (HA) embryos into 241 heifers and 84 cows of H, A, Ferrell, C. L. and T.G. Jenkins. 1985. Cow type and the nutritional environment: Nutritional aspects. J. Anim. HxA or Holstein breeds were used to study Sci. 61:725. effects of twinning on cow and calf perform- Fnxnd, R. J. and R. C. Littell. 1981. SAS for linear model. A ance. Twinning increased retained placentas, guide to the ANOVA and GLM procedures. SAS Inst., Inc.. Cary, NC. shortened gestation length (-3 d), reduced calf birth (-13%), weaning (-17%) and feedlot Garrett, W. N., G. B. Anderson, P. T.Cupps and N. Hinman. 1982.Influence of twin births on feedlot performance (-9%) weights and viability, but increased of calves. Proc. West. Sect. Am. Soc. Anim. Sci. 33: milk output (25%) and expected herd weight 177. of calves marketed at weaning (79%) and from Gregory, K. E., S. F. Echtemkamp, G. E. Dickerson and L. V. Cundiff. 1988. Twinning in cattle. In: Roc. 6th feedlot at 400 d (96%). Estimated herd input World Cong. on Anim. Prod. Paper 4.10. p 481. costs per unit of beef output value was 24% Helsinki, Finland. lower for twin than for single births. Gains Gregory, K. E., S. F. Echternkamp, G. E.Dickerson, L. V. from genetic twinning could be even greater CumW, R. M Koch and L. D. Van Vleck. 1990. Twinning in cattle: I. Foundation animals and genetic with appropriate nutrition and management, and environmental effects on twinning rate. J. Anim. and marketing at the same final weights. Sci. 68:1867. Serious efforts to utilize genetic twinning in Gum-Martinez, P. 1986. Potential effect of twinning on beef cattle are warranted. the efficiency of meat and milk production in beef cattle. M.S. Thesis. Univ. of Nebraska, Lincoln. Hendy, C.R.C. and J. C. Bowman. 1970. Twinning in cattle. Literature Cited Anim. Breed. Abstr. 38:22. Anderson, G. B., R. H. BonDurant and P. T.Cupps. 1982. Jenkins, T.G. and C. L Femll. 1984. A note on lactation curves of crossbred cows. Anim. Prod. 39:479. Induction of twins in different breeds of cattle. J. Johansson, I., B. Lindh6 and F. Pirchner. 1974. Causes of Anim. Sci. 54:485. variation on frequency of monozygous and dizygous Anderson, G. B., P. T.Cupps and M Drost. 1979. Induction twinning invarious breeds of cattle. Hereditas 78:201. of twins in cattle with bilateral and unilateral embryo Kay, R. M.,W. Little and B. A. Kithenham. 1976. A transfer. J. Anim. Sci. 49:1037. comparison of growth performance and blood comBar-Anon, R. and J. C. Bowman. 1974. Twinning in Israeli-
nutritional and other management appropriate for cattle selected for total genetic ability to consistently produce and rear twins. Although most females born twin with a male are sterile, females from like-sexed twins are fertile and total numbers of fertile females produced would be reduced only by lowered survival of twins (41 vs 44% per calving). Early ultrasonic identification of twin pregnancies will facilitate appropriate nutrition and management of twin vs single pregnancies. Twinning when induced hormonally or by embryo transfer may have advantages or disadvantages in cost or uniformity of results, but it lacks the potential improvement in total maternal adaptation for carrying and rearing twins. Although twinning rate is lowly heritable, a combination of large population screening, family and progeny testing and selection among puberal females for multiple-ovulation embryo-transfer reproduction based on repeated observation of ovulation rates promises to achieve highly useful increases in twinning rate of cattle (Gregory et al., 1988, 1990; Echtemkamp et al., 1990).
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GUERRA-MARTINEZ ET AL.
position of twin and singleton calves. Anim.Prod.22: Tuman, E. J., G. B. Laster, R. E. Renbarger and D. F. 19. Stephens. 1971.Multiple births in beef cows treated Koong, L. J., G. B. Anderson and W. N. Garrett. 1982. with w e gonadotropin (PMS) and chorionic Maternal energy status of beef cattle during single and gonadotropin (HCG). J. Anim. Sci. 32:962. twin pregnancy. J. Anim. Sci. 54480. USDA Agricultural Statistics. 1983. U.S. Government Larson,L. L., M. A. Ishak, F.G. Owen, E. D. Ericksonand S. Printing Offlce, Washington. Dc. R Lowry. 1985.Relationship of physiological factors van der Merwe, F.J. and P.Van Rooyen. 1979.Estimates of to placental retention in dairy cattle. Anim. Reprod. metabolizable energy needs for maintenance and gain Sci. 931. in beef steers of four genotypes. In: L. E. Mount (Ed.) Maijala, K. and A. Osva 1988. Genetic correlations of Energy Metabolism. pp 135-139.Publ. No. 26,Eur. twinning frequency with other economic traits in dairy Assoc. Anim. Prod. Butterworths, London. cattle. In:Roc. 6thWorld Congr. on Anim.Prod. Sect. Vincent, C. K. and A. C. Mills. 1972.Gonadotropin levels 4. Paper 4.11. p 482. Helsinki, F i . for multiple births in beef cattle. 1. Anim. Sci. 3477. Nebraska Cooperative Extension Service. 1984. Estimated Wheeler, M.B., G. B. Andemon, R. H.BonDurant and G. H. crop and livestockproductioncosts. EC 84-872.p E14. Stabenfeldt 1982. Postpartum ovarian function and Price, T.D.and J. N. Wiltbank. 1978.Dystocia in cattle. A fertility in beef cattle that produce twins J. Anim.Sci. review and implications. Theriogenology 9 195. 54589. Reid, J. P.,J. W. Wiltonand J. S.Walton. 1986.Comparative Willis, M. B. and A. Wilson.1974.Comparative reproducproductivity of cows after receiving two embryos at tive performance of Brahman and Santa Gerhudis transfer. Can. J. Anim. Sci. 66:373. cattle in hot humid environment. Anim. prod. 18:35. Rutledge, J. J. 1975.Twinning in cattle J. Anim. Sci. 40:803. Wyatt,R D.,M. B.Gould and R. Totusek. 1977.Effects of Syrstad, 0.1977.Effects of hvinningon milk in dairy cattle. single vs twin rearing on cow and calf performame. J. Livest. Prod. Sci. 4:255. Anim. Sci. 45:1409.
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P. Guerra-Mamnez2, G. E. Dickerson3, G. B. Anderson4 and R. D. Green5 University of Nebraska, Lincoln 68583-0908 and University of California, Davis 95616 ABSTRACT
Effects of twinning on efficiency of beef production were estimated from results of bilateral transfer of two Angus x Hereford (AxH) embryos into each of 241 heifers and 84 cows (H, A, HxA or Holstein x H)over 4 yr. Calves were weaned at 180 d and fed either 220 d in a feedlot (1977) or 170 d on forage and 140 d in a feedlot (1978 to 1980). Effects of parity, twinning and sex of calf were estimated as covariates within year-breed of dam. Pregnancy at 45 to 60 d of gestation was 68% in heifers (H) and 74% in cows (C), with 40% single (S)and 60% twin (T) births. Dystocia was 28% in H vs 10% in C (P e .05), and tended to be less (P > .05) for T than S in H. More placentas were retained (P c .05) for T than for S in both H (35 vs 12%) and C (24 vs 4%). Twin gestations averaged 3 d shorter and subsequent calving intervals 13 d longer (P < .05), but total calf mortality was slightly higher (P > .05). Abortions were 4% in H only. Twinning females lost maternal weight during late gestation (P c .05) when crowding limited voluntary feed intake, while fetal requirements were 60% higher (P c .01). Twins increased milk output 25% (P e .05), but 11%higher feed intake maintained cow weight during lactation. Twinning reduced birth weight 13% and weaning weight 17% (P < .05), but 400-d feedlot weight only 9% because of compensating feedlot gain. Twins gained 18% faster than S during postweaning 17O-d forage feeding, but 5% slower in feedlot to 8% lighter 490-d weight (P e .05). Assuming 40% higher veterinary and labor costs for twins, estimated integrated herd costs per unit of ageconstant output value would be lower for T than for S production by about 24% for marketing either at weaning or at 400 d. (Key Words: Cattle, Multiple Births, Growth, Reproduction, Meat Yield.) J. Anim. Sci. 1990. 68:4039-4050
as Holstein, Brown Swiss, Charolais, Simmental and Maine Anjou (Johansson et al., Twinning is relatively rare in cattle, ranging 1974; Willis and Wilson, 1974; Rutledge from less than 1% in Hereford, Angus and 1975; Reid et al., 1986). Twinning in cattle Zebu breeds to over 3% in some breeds such potentially is important for increasing efficiency of beef production because the overhead costs for maintaining single-calving cows 'Published as Paper No. 9099, Journal Sa.,Nebraska account for over 50% of total costs of beef Agric. Res. Div., Univ. of Nebraska, Lincoln. Partial production (Dickerson, 1970; 1978; 1983). publication from M.S. Thesis of senior author. Twinning could spread these cow costs over 2Present address: IDIAP, Apdo 958, David, Chiriqi, 60 to 70% more calf weight at weaning PaUallla. 'Roman L. Hruska U.S. Meat Anim. Res. Center, (Turman et al., 1971; Vincent and Mills, 1972; ARS, USDA, A218 AnS, Univ. of Nebraska, Lincoln. Bar-Anon and Bowman, 1974; Cunningham, %ept of ~nim.sci.. univ. of california, &vis. 1977; Diskin and Sreenan, 1985). However, b p t . of Anim. Sci., Texas Tech Univ., Lubbock in cattle twinning has been tempered interest 79409-2141 by various degrees of phenotypic association Received December 11, 1989. Accepted May 1, 1990. with shorter gestation, lighter birth and weanlntroductlon
4039
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4040
GUERRA-MARTINEZ ET AL.
TABLE 1. NUMBER OF R Z P I @ N T FJ3MALES ing weights, higher calf mortality, more BY BREED AND YEAR FOR BILATERAL retained placentas and the possibility of TRANSFER OF ANGUS X HEWFORD delayed rebreeding under management inEMBRYOS 5 DAYS AFTER ESTRUS tended for single calvings (Erb and Morrison, 1959; Hendy and Bowman, 1970; Wyatt et al., Year Breed Heifers Cows Total 1977; Larson et al., 1985; Guerra-Martinez, 1977 Herefordo 38 37 75 1986). Such limitations on gains from twin- 1978 Hereford 18 13 31 ning may be less important under nutrition and Angus (A) 15 16 31 management appropriate for twin-bearing 34 HxA 16 18 cows, especially in populations selected for 49 47 96 genetic ability to consistently produce and rear 1979 Hereford 31 31 twin calves (Maijala and Osva, 1988). The Angus 26 26 26 26 present study is an experimental evaluation of HxA 83 83 the effects of embryo transfer twinning on performance of cow and calf and on estimated 1980 Hereford 36 36 35 HolsteinxH 35 net costs per unit of beef output value. Experimental Procedure
Data from a 4-yr superovulation and embryo-transfer experiment conducted at the University of California-Davis (Anderson et al., 1979; 1982) were analyzed to evaluate changes in performance, in outputs and in costs from twin calvings of cows that normally would produce single calves. Earlier publications reported part of the results for effects on reproduction (Wheeler et al., 1982), maternal energy requirements (Koong et al., 1982) and feedlot performance (Garrett et al., 1982). Management. For calving in 1977, 38 Hereford (H) heifers and 37 H cows were artificially inseminated with semen fiom a Red Angus (A) bull followed by unilateral transfer 5 d after estrus of one AxH embryo into the uterine horn opposite to the corpus luteum pable 1). For calving in 1978 through 1980, one AxH crossbred embryo was transferred by midventral laparotomy into each uterine horn of a synchronized recipient female (Anderson et al., 1982). Cows and heifers of the same breed were compared only in 1977 and 1978. Heifers and cows used in 1978 were H, A and HxA. Only H, A and HxA heifers were used again in 1979 and H plus Holstein x H heifers were used in 1980. Pregnancy and number of fetuses were determined by palpation per rectum at 42 to 48 d of gestation and again at 180 to 200 d. In 1977, pregnant recipients were fed primarily chopped oat hay until changing to 50% chopped oat hay and 50% chopped alfalfa hay during the last trimester and during lactation. Both diets contained about 1.8 McaVkg DM (Garrett et al., 1982). Calves in 1977 had
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Totals
71 241
84
71 325
access to the diet of the dam and to a pelleted creep feed. In the latter 3 yr, pregnant and lactating females and their calves had ad libitum access to a diet containing 61% oat hay, 36% rolled barley, 2% cottonseed meal, .7% oyster shell and .5% trace mineralized salt; this diet contained about 2.3 McaVkg DM. No other creep feed was supplied. Each cow and her calf or calves was confined to a single pen during the suckling period. Females were observed closely at calving; deliveries that were assisted because of either large size or malposition of the calf were classified as dystocia. Ages at calving were 24 to 36 mo for heifers and 3 to 12 yr for cows. Calvings were 29% in July, 45% in August, 9% in September, 12% in October and the remaining 5% in May, June and November. Following calving, females were exposed to H bulls from 45 d postpartum until pregnancy was confirmed by palpation. Postpartum days to first ovulation and to next calving were recorded only for 1977 calvings and days open for 1977 and 1978 calvings, using weekly plasma progesterone assay to predict day of ovulation and palpation on d 42 to 48 to predict conception (Wheeler et al., 1982). Cow Weights. Females calving in 1977 were weighed each week during gestation; those calving in 1978 and 1979 were weighed at 3- to 4-wkintervals, and those in 1980 were not weighed. Because cow weights 24 h postcalving varied greatly, change in body weight during gestation (CBW) was estimated (Koong et al., 1982) as follows:
TWINNING AND EFFICIENCY OF BEEF PRODUCTION
CBW = (precalvingweight - 1.5 x calf birth weight) - initial weight (1) Both precalving and initial (WTIG) weights were calculated from within cow linear regression, using all interval weights. Gestation average daily gain (GDG) was calculated as CBW/gestation length in days, and postcalving weight (WTCAL) was estimated as follows: WTCAL = (GDGx280)+WTIG.
(2)
Cows were weighed each week during lactation in 1977 and at 3- to 4-wk intervals in 1978 through 1980. Cow weights at weaning (CWTW) were used to calculate lactation daily gain in weight (LDG), using calf age in days at weaning (AWN), as follows:
and adjusted cow weight at 180 d weaning as follows: A
m = (LDGx 180) + WTCAL.
(4)
Calf Weights. Individual calf weaning full weights (WWTC) at 170 to 190 d of age and birth weights (BWTC) were used to calculate preweaning daily gain, WDG = (WWTC-BWTC)/AWN
(5)
and adjusted 180-d calf weaning weight, AWWTC = (WDG x 180) + BWTC.
(6)
Relative preweaning percentage growth rate (WRG) of calf was calculated as follows: WRG = 200PWDG/(AWWTC BWTC).
+ (7)
Similarly, the adjusted slaughter weight (ASWTC) and percentage relative postweaning growth rate (PRGC) were calculated from postweaning daily gain (PDG), full weight at slaughter (SWTC), and age at slaughter (AS) and weaning (AWN) as follows: PDG = (SWTC- WWTC)/(AS - AWN) (8) ASWTC = (PDGx220)+AWWTC,and (9)
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PRGC = 200PDG/(ASWTC + AWWTC).
4041 (10)
For postweaning backgrounding periods on forage and for the subsequent feedlot periods in 1978 through 1980, body weight and relative growth were adjusted to 170 d and 140 d, respectively, as described above for the postweaning feedlot period. Milk Production. In 1977 through 1979, milk production was estimated by the weighsuckle-weigh method. Calves were separated from d a m s from 0600 to 1200, weighed, allowed 45 min to suckle and reweighed. The gain in calf weight multiplied by 4 was the estimated 24 h milk production. Measurements were taken weekly in 1977 from calf ages of about 15 to 121 d, but at 2 8 d intervals from calf ages of 40 d in 1978 or 28 d in 1979, until 170 to 180 d. The method of Jenkins and Ferrell (1984) was used to estimate total 18Od lactation milk yield (TMY), day of peak milk yield (TPY), peak daily milk yield (PMY) and persistency (PER = TMY/PMY). Feed Consumption and Energy Requirements. Individual cow feed consumption (MEI) was recorded weekly only in 1977, from conception to weaning of calves. Metabolizable energy requirements for pregnancy (MEP) were estimated individually from net energy gain of the conceptus adjusted for calf birth weights; those for change in cow body energy content and for maintenance (MEM) were predicted from changes in cow weight (Koong et al., 1982). The energy requirements for milk production (MEL) assumed that milk composition was 3.2% fat, 3.1% protein and 4.4% lactose, with gross energies of 9.4, 5.8 and 4.4 kcal/g, respectively, and that efficiency of ME use was 63% for milk secretion. These calculate to 1.07 Mcal ME required/kg milk produced. The MEM during pregnancy and lactation were obtained by difference by subtracting ME for changes in cow body weight and either MEP or MEL from total MEI, where MEI(Mcal/d) = 1.8 kg x DMI. In 1977, calves weaned at about 6 mo of age were fed individually a blended diet containing about 2.58 Mcal MEkg dry matter. Male calves had been castrated at about 4 mo of age. Steers were implanted with Synovex-S after about 50 d on feed. Calves were slaughtered at a typical low Choice visual grade (Garrett et al., 1982). Daily feed consumption was computed from total feed
4042
GUERRA-MARTJNEZ ET AL.
TABLE 2. SIMPLE MEANS FOR PREGNANCY AND CALVING RATES PLUS EMBRYO AND CALF SURVIVAL FROM BILATERAL EMBRYO TRANSFERS Heifers
Traits
No.of recipient females No.pregnant at 45 to 60 d %'
No.calved %'
No. with dystocia %b
No.with retained placenla %b
No.of fetuses Abmtiom, %' Other fetal loss, %' No.of calves born stillborn,%d Early mortality. %* Total lost fetuses, abc No.at 1 wk
Single
Twin
66 27.4 59 24.5 22 37.3 7 11.9 66 3.O
98 40.7 88 36.5 19 21.6 31 35.2+ 1% 4.1
59 3.4 8.5
176 7.9 11.9
52
141
COWS
All
%f all recipient females. Some dams with twins lost one em%f all females calving in each parity and type of birth.
241 164 68.1 147 61 .O 41 27.9* 38 25.8* 262 3.8 6.5 235 6.8 11.1 26.3 193
Single
Twin
All
15 17.9 23 27.4 2 8.7
47 55.9 37
62 73.8 60 71.4 6 10.0 10 16.7 109 0 11.0 97 6.2 9.3 24.8 82
84
1 4.3 15 0
44.0 4 10.8 9 24.3*
94 0
23 8.7 4.3
74 5.4 10.8
20
62
after 60 d.
'Of total fetuses at 45 to 60 d in each parity.
'bf all
calves born for each parity and type of birth.
+P < .05.
(as-is) intake (TF,kg) and days on feed (DF); feed conversion ratio (FRC) was calculated from TF and weight gain (G, kg) on feed as TF/G. Proportion of observed intake utilized for maintenance (MEM) vs gain (MEG) was estimated from partial regression on mean metabolic size (W75) and G (van der Merwe and Rooyen, 1979). In 1978 through 1980, weaned calves were reared on forage without recording feed intake for 145 to 230 d; calves then were fed individually for 127 to 153 d. Records were adjusted by covariance to 170 d on forage and to 140 d in feedlot. Feedlot records for 1978 through 1980 were utilized as described above for 1977 data. Statistical Analyses. Heifer vs cow contrasts were balanced within year and breed of recipients for 1977 and 1978, but only heifers were used in 1979 and 1980 (Table 1). Single vs twin contrasts occurred with variable frequencies within year-parity subclasses, as did male vs female contrasts within yearparity-twinning subclasses. Therefore, a sequential analysis of variance (Type I SS) was utilized to estimate effects of parity (P), twinning (T)and sex (S) of calf as covariates, after fitting the fixed effects of year and breed (B) of recipient (Freud and Littell, 1981). All two-, three- and four-way interactions were
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examined and the nonsignificant ones were excluded from the final models, using residual error for tests of significance. Results and Discussion
Reproduction and Lactation. Simple mean pregnancy rates for cows vs heifers were 74 vs 68% at 45 to 60 d of gestation and 71 vs 61% at calving, with a higher proportion of twin pregnancies for cows (76 vs 60%) at 45 to 60 d but not at calving (62 vs 60%, Table 2). Dystocia was more common for heifers than for cows (28 vs 10%.P < .05) and was slightly more common (P > .05) for heifers with twin than with single calves (37 vs 22%). For single calves, dystocia was primarily due to the large calf size relative to pelvic area (Price and Wiltbank, 1978), but for twins assistance was for repositioning one or both calves to facilitate delivery. Voluminous literature reports are inconclusive concerning the effect of twinning on dystocia (Guerra-Martinez, 1986), perhaps because of different definitions of dystocia. Retained placentas were more frequent (P < .OS) for heifers than for cows (26 vs 17%),and also for twins than singles (P < .05) in both heifers (35 vs 12%) and cows (24 vs 4%).
4043
TWINNING AND EFFICIENCY OF BEEF PRODUCTION
TABLE 3. LEAST SQUAREs MEANS FOR TWIN (T) VS SINGLE (S) CALVING OF HEIFERS AND cowsa
cows
Heifers
S
Traits
Gestation period, 280 d Wt at conception, kep Gestationwtgain, db Wt after calving, kggb Gestation length, da Last trimester, 95.dc Change in maternal body wt, g/d MEI, i n t a k e b ~ gk~W ~, d MEM, maintenance/k 75, k W d MEP,pregnancyBg 7! kcUd
TIS, %
T
351.6 290 432.4 276
335.7 330 428.1 280 5 187 144 44
-356 176 137 64
105 88"
101 98.6; -7,120+ 94 95* 153;;
TIS, 96
T
S
403.5 240 470.1 280
90 179 135 38
454.4 160 497.9 278 -568 170 159 64
113 67; 106 99.0* -631. 95 118* 170+*
(MEM+MEP)
MEI
/kg7',kCaUd
Lactation, 180 da Wt gain, g/d Wt at weaning, k Mid-lactation,Wg.. kg MEI,intake/kg'15, kcad' MEM, maintenance g75, kcad' MEL.lactatioqkg7/: kcal/dc
m&m)m75, kWdC Total 180-d milk yield, kgb Peak milk yield, kg/db Persistency, totaVpeakb Calving to 1st ovulation, dC Calving to conception, dd - interval, dc Calving
bats from bData from 'Data from %ata from
1.14
114
460 520.8 101.7 289 193 71
480 526.7 102.5 307 193 87
104 101 101 106* 100 123
360 546.3 107.0 264 196 57
.91 1,233 8.8 132 50 68 356
.91 1.5% 11.4 133 68 87 364
100 129 13P 101 134* 128 102
1,075 8.1 128 62 88 368
1 .00
.97
.%
1.31 380 5702
134 105
308 200 85
104 104 117* 102 149;
.93 1,305 9.3 123 70 86 387
96 121 115. 96* 113* 98 105*
111.1
1977 through 1980, except as noted. 159 female calvings in 1977 through 1979, for body weight excluding uterine content. 56 females calving in 1977 when diet during last himester contained 1.8 Mcal m/kgDM. 83 females calving in 1977 and 1978. all females calving,
*P < .05. **P < .01.
These results are in general agreement with the literature (Vincent and Mills, 1971; Diskin and Sreenan, 1985; Guerra-Martinez, 1986). First postpartum ovulation following twin births in 1977 data (Table 3) was delayed (P e .01) in both heifers (68 vs 50 d) and cows (70 vs 62 d); the corresponding differences (P e .05) in the subsequent calving interval were 8 and 19 d. However, in the combined 1977 and 1978 data, the corresponding differences in days open were nonsignificant (19 and -2 d), perhaps because energy density of the diet fed during the last trimester of pregnancy was increased from 1.8 to 2.3 Mcal ME/kg DM in 1978. Gestation length was 3 or 4 shorter (P < .01) for twin-bearing cows or heifers; this makes the calving interval shorter but makes subsequent days open and calving intervals
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longer, especially when associated with retained placentas. Most of the literature concerning effects of twinning on reproduction are for dairy cattle (reviews by Hendy and Bowman, 1970; Bu-Anon and Bowman, 1974; Syrstad, 1977; Chapin and Van Vleck, 1980) and clearly demonstrate longer days open and calving intervals following twin biahs. Wyatt et al. (1977) also observed that adoption of a second newborn calf at parturition delayed postpartum ovulation in Hereford x Holstein crossbred cows. Females producing twins in 1977 to 1979 were somewhat heavier (P > .05) than single calvers at conception (Table 3), but their weight gain during gestation was 12% less in heifers and 33% less in cows (P e .05), so that weight after calving was only slightly above
4044
GUERRA-MARTINEZ ET AL.
that of single calvers. Energy content of the diet was about 1.8 Mcavkg DM in 1977 and 2.3 Mcavkg DM in 1978 and 1979. During the last 9 5 d trimester for 1977 data, the carrying of twin fetuses caused losses in maternal body weight of 34 kg in heifers and 54 kg in cows, compared with gains of .5 and 8.5 kg, respectively, for single calvers (P < .05). Energy intake in 1977 was 5 or 6% less for twinning females, presumably because abdominal crowding limited physical capacity. Calculated requirements for pregnancy were higher for those carrying twins in both heifers (53%) and cows (70%); hence, energy requirements exceeded energy intake in 1977 by 14 and 34%, respectively. The earlier report on the 1977 part of this experiment by Koong et al. (1982) concluded that a higherenergy diet would be required both to prevent loss of weight by beef cows carrying twins and perhaps to reduce the incidence of delayed rebreeding following twin births. During lactation in 1977, voluntary feed energy intake per kg.75 of body weight was higher (P c .05) for twinners by 6% in heifers and by 17% in cows (Table 3), thus meeting the 23 and 49% higher energy requirements
associated with 29 and 21% greater (P < .05) estimated milk production, and allowing slightly greater (P > .05) gains in weight for twinners of 4%in heifers and 5 % in cows. The estimated energy required for maintenance was higher during lactation than during late gestation (196 vs 145 K c a U l ~ gx. ~d-l); ~ both were somewhat higher than reported by Ferrell and Jenkins (1985) for beef cows. However, estimated maintenance requirements were no higher for the cows nursing twins. Effects of twin calves on milk production are different for suckler beef production than for dairy cows, because milk output is limited by milk demands of the calves, which are greater for twins. Studies with dairy cattle (Syrstad, 1977) have indicated that milk production increases after cows produce twins but is lower for cows carrying twin calves. The low energy content of the 1977 diet could have limited milk yield by dams nursing twin calves. Calf Performance. Abortions were rare and occurred only in heifers (4%; Table 2). Of all fetuses counted at 45 to 60 d gestation, 10 to 11% were lost before birth by either absorption or abortion, and another 14 to 16% died at birth or before 1 wk of age. Calf mortality
TABLE 4. LEAST SQUARE!S MEANS FOR ' I "(T) AND SINGLE (S) INDIVIDUAL CALWS FROM HEIFERS AND COWS, BY SEX OF steers Traits
Dam
Wt at birth, kg
Heifer cow
Reweaning 180 d Wt gain, W d Relative growth, %/d 18bd wt, kg
Heifer cow Heifer cow Heifer
cow
T
S 34.0 31.6 37 .95 .77
.a2 190.7 206.0
27.7 29.8 .71 .79 .75 .77 157.1 172.4
Heifers
TIS,% 82,
94, 82* a3* 97
94 a2*
u*
s
T
26.7 33.7 .83
.91 .82 .79 181.7 197.0
TIS,%
Au TIS,%
23.6 28.8
a8* a3*
a5* a9*
.67 .75 .77 .79 148.1 163.4
ai* 82. 94
ai*
loo a2*
a3*
a3* 96
97
a2* a3*
Postweaning 220 db 206.5 155.2 75* 181.3 150.6 Initialwt,kg 1.27 121 95 1.03 1.09 Wt gain, W d A1 111* .37 .39 Relative growth, %/d .35 6.4 6.2 97 6.7 6.3 FWgain. kg DM/kg 485.9 421.4 a7* 407.9 390.5 W d w, kg 346 290 84* 295 270 Mid wt, kg F e e d i n t i ~ k e ~kcad ~* 259 278 107* 265 268 Maintenance&'5, kcdd 1 a0 174 97 la3 iai Maintenancefitake. % 69.5 62.6 90, 69.0 67.5 -or 272 calves from yr 1977 through 1980, except that postweaning feedlot data were for only bAssuming 2.58 Mcavkg dry matter intake (Garrett et al., 1982). Data b o r n 1977 only.
*P < .05.
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a3* 106 111*
94 %*
92 1.01
79* 100 111 95 91
aa* 104
98 98 94* 60 calves in 1977.
99
4045
" N I N G AND EPPICIENCY OF BEEF PRODUCTION TABLE 5. LEAST SQUARES MEANS FOR POSTWEANING PERFORMANCE OF 134 TWIN 0 AND 73 SINGLE (S) CALVES DURING BACKGROUNDING (180 TO 350 DAYS) AND FEDLOT (350 TO 490 DAYS) PERIODS IN 1978 TO 1980 Steers
S
Trait 180 to 350 d Gain, IEB G d d ,g Relative growth, %/d 350-M kg 350 to 490 d Gain, kg Gain/d, g Relative growth, %id 4 W d wt, kg Mid wt. kg Feed/gain, kg DM/kg Feed intake/kg h a d a MaintenancenEgY5,kcaVdb Maintenance/intake, %
''
T 51.6 303 .136 248
220 1,575 ,423 457 349 5.94 293 20 1 68.6
Heifers TIS. %
60.9 358 .187 224
118. 118* 138* 91*
209 1,495 .433 420 315 5.70 293 201 68.6
95* 9 s 1m* 92* 90 97* 100 loo* 100
S
T 51.0 300 .I45 233
205 1,465 .411 427 323 6.11 2% 201 67.9
TIS. % 60.3 355 .196 210
118. 118* 135*
194 1,385 .421 390 292 5.94 295 201 68.1
95* 95* 1U2* 91* 90 97* 100 100
w
100
'Assuming 2.58 M M g dry matter in diet (Garrett et al., 1982). % s e d on partial regression within breed-year-sex-twinning classes of ME intake on W75and daily gain. *P < .05.
from birth to 1 wk was only slightly higher (P > .05) in twins than in singles from the 147 heifers (20 vs 12%) and 60 cows (16 vs 13%) calving. In numerous studies of calf mortality in dairy cattle (reviews by Erb and Morrison, 1959; Bar-Anon and Bowman, 1974; Johansson et al., 1974), mortality of twin calves was several times higher than for singlebom calves, especially in males. Twin calves were lighter at birth (P c .05) by 15% from heifers and by 11% from cows (Table 4). heweaning gain also was less (P < .05) for twins than for singles by 19% from heifers and by 17% from cows. heweaning weight gain relative to size (%) was only 3 or 4% slower for twins, but weight at 180 d weaning was 16 to 18% lower for twins in both sexes and both parities (P c .05). Studies of twinning from hormoneinduced multipleovulation (Turman et al., 1971; Vincent and Milk, 1972; Bellows et al., 1974) all have reported about 25% lower birth weight for twin- vs single-born calves. Weaning weights of twins with access to creep feed (Turman et al., 1971; Diskin and Sreenan, 1985) were only 14 to 18% below weights of singles, but when creep feed was not available (Vincent and Mill, 1972), twins were 26% below singles in weaning weight. Thus, under creep feeding and ignoring differences in calf crop reared, cows with twins would produce 65 to 70% more weight of calves weaned.
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During the 220-d feedlot period for 1977 calves (Table 4), weight gain of twins vs singles was 5% slower for steers and 6% faster than for heifers, but in both sexes, gain relative to size was 11% faster for twins (P c .OS), because initial weights in feedlot were less for twins than for singles by 24% in males and 16% in females. Thus, the 4OOd slaughter weight was less for twins than for singles by 13% in steer calves and by only 4% in heifer calves (P c .05). Feedgain ratio was only slightly (P > .05)lower (-5%) for twins than for singles. Feed energy intake was 7% higher for twin than for single steers (P c .05) but only 1% higher for twin females. Estimated maintenance requirements per weight75 (van der Merwe and Rooyen, 1979) were only slightly lower for twins of either sex, as reported by Garrett et al. (1982). Thus, the maintenance proportion of total energy intake was less (P < .05) for twins than for singles in steers because of their 16% lower mean weight. During the postweaning 145 to 230 d backgrounding period on forage for the calves in 1978 to 1980, both steer and heifer twins gained 18% faster than singles (P< .05, Table 5). Relative growth rate was faster for twins by 38% in steers and 35% in heifers, so that adjusted 350d weight was less for twins by only 9% in steers and 10% in heifers (Pc .05).
4046
GUERRA-MARTINEZ ET AL.
During the following 127 to 153 d in feedlot, the sets of twins in 1978 to 1980 gained 5% slower than singles in both steers and heifers (P e .05). However, relative growth rate was 2% faster for twins than for singles in both sexes (P < .05) because initial weights were 9 or 10% lower for twins. Both voluntary feed consumption and estimated maintenance requirements per kilogram body weight75 were similar for twins and singles of both sexes, but weight maintained was 10% lower for twins. Although the maintenance propodon of total feed intake was 68 or 69% for twins and singles of both sexes, maintenance was reduced more than gains in twins, leading to 3% lower feed/gain for twins. Total ageconstant 490-d slaughter weight output per female producing twins that survived to market age would be about 83% greater than for females marketing singles. Or course, the higher mortality of twin calves and the greater mortality or culling of twinning cows would reduce the advantages of twinning. However, the freemartin heifers born twin with a male would increase market output, in addition to those from the female twin sets in excess of replacements needed, so that the proportional increase in output above replacement needs would be greater than for total calves reared. Also, feeding twin calves to the same final weight would increase output relative to cow overhead even more. As in the present study, Turman et al. (1971) and Davis (1989) found that twin calves creep-fed to weaning gained about as rapidly as singles in the feedlot, and more rapidly relative to weight maintained (Table 4). Thus, only the disadvantage in weaning weight remained at an ageconstant feedlot endpoint; feedlot gain for twins would be at least as efficient as that for singleborn calves. Similarly, both Kay et al., (1976) and Diskin and Sreenan (1985) found that twin-born calves closely approached the weight of singleborn calves (96 or 98%) at the end of an a g e constant postweaning feeding period. InputlOutput Eficiency. A specific example of input costs and output value is presented here to illustrate potential economic gains from a high frequency of genetic twinning in beef cattle under midwestern U.S.cowcalf-feedlot conditions. The performance data used were for twinning obtained from embryo transfer to females of breeds that normally produce single calves. Also, the fact that these twin-bearing
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heifers and cows in 1977 data lost 34 and 54 kg, respectively, of empty body weight during the last trimester suggests that improved nutrition in late gestation could reduce some of the adverse effects on reproduction and mortality. Further, the estimated non-feed costs per cow for veterinary care and labor were assumed to be 40% higher for twin than for single calvings. Such calculated economic gain from twin calf production should be a conservative estimate of the potential gain from using cattle genetically selected for consistent twin calf production. Estimated input costs for feed, veterinary labor and overhead by segments of the year and for rearing replacements from weaning to breeding age are shown for heifers and cows
TAB= 6. ESTIMATED INPUT COSTS ($) PER HEIFER (H) AND COW (C) CALVING FOR SINGLE (S) AND TWIN CALF PRODUCTION^
0
H Periodhem
S
C
T
S
T
Lactalion (180 d) 146.42
Feed8 otherb
156.41
141.03
169.62
81.19 108.81 81.10 109.36 -
Subtotal 227.61 265.22 221.13 278.98 Second trimester (90d) Feed8 22.95 22.14 24.57 23.76 25.14 33.73 25.38 34.47 otherb Subtotal 48.09 55.87 49.95 58.23 Third trimester (95 d) Feed8 39.99 39.11 40.74 42.20 38.65 52.42 38.17 51.% otherb -
--
--
Subtotal Replacements'
Feed
78.64
91.53
78.91
94.16
35.77
38.52
40.35
44.02
65.03
70.03
73.37
80.04
29.26 31.51 33.02 36.02 -
Other subtotal
~~~
%at
a-
~
or oat-alfalfa hay @ &/kg, salt + minerals @ &/
'Costs during 2nd and 3rd himester and 180-d lactation, respectively, for single births were $2.25. 4.00 and
5.50 for veterinary and medicine and $15.00, $27.50 and $55.00 for labor, but were 40% higher for twin births. These costs were about 5% higher during 2nd trimester when open cows held for culling overlap &eir replacements. Overhead costs added = 10% of all feed and cash costs. cAssUming replacement rates of 19.5, 21.0, 22.0 and 24.046 for HS,HT,CS and Cr,respectively, and $333.50 cost from weaning to breeding for each replacement f s male (Nebr. Coop. Ext. Sen., 1984).
4047
" N L N G AND EFFICl€?NCY OF BEEF PRODUCTION TABLE 7. PREDICITD I " U T / O W U T ($/KG) PER COW CALVING FOR HEIFERS, COWS AND HERD PRODUCING SINGLE VS TWIN CALVES MARKETED AT WEANING Heifers
COW
Herda
Twin/ Twill
Single
Total input, $ Feed Other
174.24 226.47 177.67 231.81 176.94 230.57 -
Total Total output,kg weaned catf-salesb Cull cows equiv' Total
245.13 419.37 128.8 59.2 188.0
$Cos@ output Feed Other Total
Single
256.18
246.69
482.65
279.60
424.36
213.4 63.3 -
Twin
511.41
132.0
242.2
71 .O -
276.7
203.0
79.7 321.9
Single
single, %
Item
Twin
246.36
274.14
423.30
504.71
119%
131.3
235.5 75.9
179% 111%
311.4
156%
68.5 199.8 1.23
.88
.89 .74 - - - 2.22
1.74
2.08
111% 130%
159
2.12
1.62
71% 83% 76%
%sed on replacement female rates of single and twincalving heifers and cows of 19.5, 21.0, 22.0 and 24.0% respectively, including COW mortality of 2% for single and 2.5% for twin calvers, with heifer/cow ratios of .272 for singles and .302 for twinning herds. %sed on mortality for single vs twin calves of 11.8 vs 19.9% from heifers and 13.0 vs 162 from cows, e.g., .441 (190.7) + ( 4 1 - .195) (181.7) = 128.8 kg for heiiers with singles. cCull cows valued at 65% of $134.39/100 kg of live weight for weaned calves (VSDA, 1983), e&, (.195 - .MO) (520.8) (.65) = 59.2 kg for heifers with singles.
rearing single and twin calves in Table 6. Rates of ME i n t a k e / ~ t were . ~ ~ based on 1977 data but applied to weights maintained by single and twin calvers in 1977 through 1980 data, by periods. Other cost figures were from the Nebraska Cooperative Extension Service (1984). Relative prices of inputs and outputs remain reasonably stable even though prices change over time. These costs then were
combined with expected market output of weaned calves and cull cows, in terms of weaned calf equivalent value, for herds producing only single or only twin calves (Table 7). F'roportion of firstcalf heifers was higher for the twinning herd (23 vs 21%) because of slightly higher mortality and culling of cows. Estimated costs for the twinning herd were higher by 11% for feed, 30% for other and
TABLE 8. PREDICTED 220-DAY FEEDLOT INPUT/OWUT FER WEANED SINGLE AND TWIN CALF MARKETED
cow
Heifer Item Total inputs $ Feeda otherb 13% Price lossC Total costs output Feedlot gain cosvkg feedlot gain $
Single
Twin
44.34
32.64
26.75
35.32
29.43
185.34
167.98
182.94
179.07
238.9
23 1.2
235.4
241.1
.727
102.70 44.92
Twin
107.32 45.38
,776
96.89
Single
.777
104.54 45.10
.743
%$/Kg for feed, 3$/rcp for salt/mineral. Equal numbers of steers and heifers.
bveterinary medicine $4.00,labor $27.50, plus 10% of feed and other costs (Nebr. Coop. Ext. Sew., 1984). 'Assuming prices per 100 kg of $134.39 for weaned calves and $116.86 for W d slaughter animals and no mortality (USDA, 1983).
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4048
GUERRA-MARTINEZ ET AL.
19%in total. Weaned calf sales for twins were 79% greater, partly because of the smaller proportion of the female calves required as replacements (i.e., approximately 28% vs 50%, allowing marketing of all of the expected freemartin heifers; 50% of heifers born), compared with a single calving herd. Cull cows marketed would increase only 11% for the twinning herd. Estimated costs per unit output of weaned calf equivalent would be reduced by 29% for feed, 17% for other costs and 24% in total. Feedlot inputloutput economic efficiency for the single and twin steer and heifer calves weaned in 1977 is illustrated for one set of 1984 input prices in Table 8. The difference in price between slaughter weight at 400 d and weaned calves at 180 d ($116.86 vs $134.34/ 100 kg live weight) for the same time period is part of the input cost for weight gained in the feedlot operation. Cost per unit of feedlot gain marketed at 400 d of age would be higher for single than for twin calves (78 vs 73$/kg) because of the 11% faster relative growth rate of twin calves and consequent 5% lower proportion of feed intake required for maintenance (Table 4). However, when fed to the same market weight as singles (10% higher, Table 4), twins would lose part of their advantage in compensatory gain. In an integrated cowcalf-feedlot operation, survival of all single and twin steer and heifer calves born from first and later parities placed in feedlot would be similar to those for calves marketed at weaning (Table 7), about 87% for singles vs 82% for twins. This difference in mortality and in the proportion of heifer calves weaned that were available for feedlot marketing (44/87 vs 59/82) determine the fraction of feedlot costs and outputs/calf (Table 8) represented in the summary of integrated input/ output per cow calving (Table 9). Cow herd costs and weaned calf outputs are from those shown in Table 7. Calf feedlot costs per cow calving are higher for twins by 103% in feed and by 110% in other items, because of the smaller proportion of female calves needed as replacements and despite the higher mortality of twins. Slaughter calf output at 400 d of age also is 96% higher for twins for some of the same reasons. Thus, calculated total costs are 36% higher but total slaughter calf equivalent output value is 79% higher and total input/ output is 24% lower for cows producing twin calves. The reduction is 26% in feed costs, but
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TABLE 9. SUMMARY OF PREDICTED INPUT1 OUTPUT PER COW CALVING FOR INTEGRATED COW-CALP-PEEDLOT PRODUCTION OF SINGLES VS TWIN C A L W MARKETED AT 400 DAYS OF AGE Single Inputs, $ Feed Cowherd Feedlot Total
246.36
Twin
TIS,480
274.14
111
70.15 142.32 - 203 316.51
416.46
132
176.94
230.57
130
2M.10 523.61
293.76 710.22
142 136
302.8
594.6
1%
Other
Cowherd Feedlot Total Total output, kga W d slau. wt cullcow equiv. Total Inputkg output, $ Feed 0thTotal
30.16 63.19 - 210
79.0 87.6 111 381.8 .83
682.2 .61
.54 - .43 -
1.37
1.04
179 74 80 76
Y u U cows valued at 75% of slaughter calf price.
Mortality 13% for single and 18% for twin calves.
only 20% in other costs, largely because 40%
higher cowherd costs for labor and other nonfeed items were assumed for cows producing twins (Table 6). If twin and single calves are marketed at the same weight rather than at the same age, the reduction in cow overhead costs per kilogram of output combined with some increase in feedlot costs for twins would be expected to lower costs/output even more than 24%. The primary reason for interest in twin beef calf production is the potential reduction of one-fourth or more in cost per unit of market value from spreading cow herd costs over greatly increased output. Relative potential for improved efficiency from twincalf production is much less when the major output is milk for human consumption. Historically, selection has not favored twinning, mainly because the handicap in calf birth weight, viability, and preweaning growth has discouraged use of twin-born sires, especially under more traditional extensive systems of production. However, the increased efficiency of beef production from twinning is substantial even under the moderate nutritional environments reported here, and can be increased further by strategic
TWINNING AND EFmcTwcy OF BEEP PRODUCTION
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Friesian d a q herds. Anim. Prod. 18:109. Bellows, R. A,, R. E. Short, J. J. Urich and 0. F. Pannish. 1974. Effects of early weaning on post-partum reproductionand growth of calves born as multiples or singles. J. Anim. Sci. 39:589. Chapin, C. A. and L. D. Van Vleck. 1980. Effects of twinning on lactation and days open in Holsteins. J. Dairy Sci. 63:1887. cunningham, E. P. 1977. ZUchterisch konsequenzen dor aonwendung n d e r biolichnischen verfahren beim Rind. Zuechtungskunde 49449. Davis, M. E. 1989. Use of embryo transfer to produce twinning in beef cattle: postweaning performance of calves. Livest. Prod. Sci. 23:295. Dickerson, G. E. 1970. Efficiency of animal productionmolding the biological components. J. Anim. Sci. 30 849. Dickerson, G. E. 1978. Animal size and efficiency-basic concepts. Anim. Prod. 27367. Dickerson, G. E. 1983. Potential genetic improvements in the efficiency of beef production. In. Y.Yamada (Ed.) Strategies for Efficient Beef Production, Proc. Int. Symp. on Beef Prod. pp 85-119. Kyoto, Japan. Diskin, M.G. and J. M. Sreenan. 1985. Production and management aspects of single and twin-bearing beef cows. Anim. Prod. 40:533 (Abstr.). Echternkamp, S. E., K. E. Gregory, G. E. Dickerson, L. V. Cudiff, R M. Koch and L. D. Van Vleck. 1990. Twinning in cattle: U. Genetic and environmental effects on ovulation rate in puberal heifers and postpartum cows and the effects of ovulation rate on embryonic m i v a l . J. Anim. Sci. 68:1877. Erb, R. E. and R. A. Morrison. 1959. Effects of twinnin8 on Implications reproductive efficiency in a Holstein-Fresh herd. I. Dairy Sci. 42512. Transfer of Hereford x Angus (HA) embryos into 241 heifers and 84 cows of H, A, Ferrell, C. L. and T.G. Jenkins. 1985. Cow type and the nutritional environment: Nutritional aspects. J. Anim. HxA or Holstein breeds were used to study Sci. 61:725. effects of twinning on cow and calf perform- Fnxnd, R. J. and R. C. Littell. 1981. SAS for linear model. A ance. Twinning increased retained placentas, guide to the ANOVA and GLM procedures. SAS Inst., Inc.. Cary, NC. shortened gestation length (-3 d), reduced calf birth (-13%), weaning (-17%) and feedlot Garrett, W. N., G. B. Anderson, P. T.Cupps and N. Hinman. 1982.Influence of twin births on feedlot performance (-9%) weights and viability, but increased of calves. Proc. West. Sect. Am. Soc. Anim. Sci. 33: milk output (25%) and expected herd weight 177. of calves marketed at weaning (79%) and from Gregory, K. E., S. F. Echtemkamp, G. E. Dickerson and L. V. Cundiff. 1988. Twinning in cattle. In: Roc. 6th feedlot at 400 d (96%). Estimated herd input World Cong. on Anim. Prod. Paper 4.10. p 481. costs per unit of beef output value was 24% Helsinki, Finland. lower for twin than for single births. Gains Gregory, K. E., S. F. Echternkamp, G. E.Dickerson, L. V. from genetic twinning could be even greater CumW, R. M Koch and L. D. Van Vleck. 1990. Twinning in cattle: I. Foundation animals and genetic with appropriate nutrition and management, and environmental effects on twinning rate. J. Anim. and marketing at the same final weights. Sci. 68:1867. Serious efforts to utilize genetic twinning in Gum-Martinez, P. 1986. Potential effect of twinning on beef cattle are warranted. the efficiency of meat and milk production in beef cattle. M.S. Thesis. Univ. of Nebraska, Lincoln. Hendy, C.R.C. and J. C. Bowman. 1970. Twinning in cattle. Literature Cited Anim. Breed. Abstr. 38:22. Anderson, G. B., R. H. BonDurant and P. T.Cupps. 1982. Jenkins, T.G. and C. L Femll. 1984. A note on lactation curves of crossbred cows. Anim. Prod. 39:479. Induction of twins in different breeds of cattle. J. Johansson, I., B. Lindh6 and F. Pirchner. 1974. Causes of Anim. Sci. 54:485. variation on frequency of monozygous and dizygous Anderson, G. B., P. T.Cupps and M Drost. 1979. Induction twinning invarious breeds of cattle. Hereditas 78:201. of twins in cattle with bilateral and unilateral embryo Kay, R. M.,W. Little and B. A. Kithenham. 1976. A transfer. J. Anim. Sci. 49:1037. comparison of growth performance and blood comBar-Anon, R. and J. C. Bowman. 1974. Twinning in Israeli-
nutritional and other management appropriate for cattle selected for total genetic ability to consistently produce and rear twins. Although most females born twin with a male are sterile, females from like-sexed twins are fertile and total numbers of fertile females produced would be reduced only by lowered survival of twins (41 vs 44% per calving). Early ultrasonic identification of twin pregnancies will facilitate appropriate nutrition and management of twin vs single pregnancies. Twinning when induced hormonally or by embryo transfer may have advantages or disadvantages in cost or uniformity of results, but it lacks the potential improvement in total maternal adaptation for carrying and rearing twins. Although twinning rate is lowly heritable, a combination of large population screening, family and progeny testing and selection among puberal females for multiple-ovulation embryo-transfer reproduction based on repeated observation of ovulation rates promises to achieve highly useful increases in twinning rate of cattle (Gregory et al., 1988, 1990; Echtemkamp et al., 1990).
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position of twin and singleton calves. Anim.Prod.22: Tuman, E. J., G. B. Laster, R. E. Renbarger and D. F. 19. Stephens. 1971.Multiple births in beef cows treated Koong, L. J., G. B. Anderson and W. N. Garrett. 1982. with w e gonadotropin (PMS) and chorionic Maternal energy status of beef cattle during single and gonadotropin (HCG). J. Anim. Sci. 32:962. twin pregnancy. J. Anim. Sci. 54480. USDA Agricultural Statistics. 1983. U.S. Government Larson,L. L., M. A. Ishak, F.G. Owen, E. D. Ericksonand S. Printing Offlce, Washington. Dc. R Lowry. 1985.Relationship of physiological factors van der Merwe, F.J. and P.Van Rooyen. 1979.Estimates of to placental retention in dairy cattle. Anim. Reprod. metabolizable energy needs for maintenance and gain Sci. 931. in beef steers of four genotypes. In: L. E. Mount (Ed.) Maijala, K. and A. Osva 1988. Genetic correlations of Energy Metabolism. pp 135-139.Publ. No. 26,Eur. twinning frequency with other economic traits in dairy Assoc. Anim. Prod. Butterworths, London. cattle. In:Roc. 6thWorld Congr. on Anim.Prod. Sect. Vincent, C. K. and A. C. Mills. 1972.Gonadotropin levels 4. Paper 4.11. p 482. Helsinki, F i . for multiple births in beef cattle. 1. Anim. Sci. 3477. Nebraska Cooperative Extension Service. 1984. Estimated Wheeler, M.B., G. B. Andemon, R. H.BonDurant and G. H. crop and livestockproductioncosts. EC 84-872.p E14. Stabenfeldt 1982. Postpartum ovarian function and Price, T.D.and J. N. Wiltbank. 1978.Dystocia in cattle. A fertility in beef cattle that produce twins J. Anim.Sci. review and implications. Theriogenology 9 195. 54589. Reid, J. P.,J. W. Wiltonand J. S.Walton. 1986.Comparative Willis, M. B. and A. Wilson.1974.Comparative reproducproductivity of cows after receiving two embryos at tive performance of Brahman and Santa Gerhudis transfer. Can. J. Anim. Sci. 66:373. cattle in hot humid environment. Anim. prod. 18:35. Rutledge, J. J. 1975.Twinning in cattle J. Anim. Sci. 40:803. Wyatt,R D.,M. B.Gould and R. Totusek. 1977.Effects of Syrstad, 0.1977.Effects of hvinningon milk in dairy cattle. single vs twin rearing on cow and calf performame. J. Livest. Prod. Sci. 4:255. Anim. Sci. 45:1409.
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