FEED INTAKE AND WEIGHT GAIN OF GROWING GOATS FED DIETS OF VARIOUS ENERGY AND PROTEIN LEVELS'
Langston University2, Langston, OK 73050 ABSTRACT
Growing goats, 45 Alpine and 45 Nubian, were used in a 3 x 3 factorial arrangement to quantify the influence of dietary energy and protein levels on daily DM intake and nument utilization for growth. Goats had ad libitum access to complete mixed diets containing either 2.46, 2.77 or 3.05 McaI/kg ME plus 11.2, 12.7 or 15.1% CP for 16 wk. Dry matter intake decreased curvilinearly as dietary ME density increased (P < .001). Dry matter intake increased linearly ( P < .OS) as dietary CP level increased during all growth intervals except wk 25 to 28 of age. Average daily gain was 115, 113 and 99 g/d for goats fed diets containing 2.46, 2.77 and 3.05 Mcal/kg ME, respectively. Average daily gain was 104, 106 and 117 g/d for goats fed diets with 11.2, 12.7 and 15.1% CP, respectively. Dry matter intake was higher (P < .01) for Alpine than for Nubian goats, whereas ADG was similar between breeds. Intake of ME was 248, 260 and 198 k ~ a l / ( k g . ~ ~for . d )goats fed the lowmedium- and high-energy diets, respectively. Intake of CP was 9.1, 10.7 and 13.2 g/ (kg 75.d) for goats fed low-, medium- and high-protein diets, respectively. Average requirements for growth derived from regression analysis of all data points were 4.6 kcal ME and .26 g CP/g ADG. The prediction equation for intake of growing goats of 4 to 8 mo of age was: DMI, g/d = 1,749 - 496 DE, kcal/g + 18 live weight, kg + 3 ADG, g/d; r2 = .73 (Sy.x = 127, P < .OOO1,n = 90). The requirement of ME for growth was 33% lower than the value recommended in 1981 by the National Research Council. (Key Words: Goats, Growth, Intake, Energy, Protein.) J. h i m . Sci. 1990. 68:1751-1759
(NRC, 1978, 1985). The protein requirement for goats is the mean of ,274, .139 and .173 g The National Research Council indicated digestible protein (DP)/g of gain based on that 7.25 kcal ME and .284 g CP were required calorie-to-protein ratios (Devendra, 1967; per gram of gain by goats (NRC, 1981). This Akinsoyinu, 1974 Rajpoot, 1979). Because of requirement is the mean of 10.18, 5.14, and the relatively small number of observations in 6.43 kcal ME/g of gain derived from experi- these three studies and the difference in intake ments that utilized indigenous Malaysian and growth rate between goats produced in goats, West African dwarf goats and various tropical versus temperate zones, protein rebreeds of Indian goats, respectively (Devendra, quirements for growth need further evaluation. 1967; Akinsoyinu, 1974; Rajpoot, 1979). This This study 1) investigated the effect of dietary mean ME requirement, with a coefficient of energy and protein concentrations on utilizavariation of 36%, is considerably greater than tion of nutrients for growth, 2) estimated DMI the requirements for dauy cattle and sheep, in growing goats and 3) estimated energy and 2.90 and 3.32 kcal ME/g of gain, respectively protein requirements of growing goats. Introduction
Materialsand Methods €XI.
'Scientific Paper Number OKLP-107,A&. hog. 2 ~ Inst.. for Goat RCS. Received May 30.1989. Accepted October 22.1989.
Res. and
Ninety growing goats, 45 Alpine and 45 Nubian, 18 male castrates and 27 female of each breed, were used in a 16-wk continuousfeeding experiment. Animals (16 wk of age)
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C. D. Lu and M. J. Potchoiba
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LU AND POTCHOIBA
TABLE 1. COMPOSITIONa OF DIETS FED TO GOATS ~
~~
Item
saltc
HH
HM
HL
MH
34.4 3.8 .7 .I 9.4
34.3 .9 .7
49.7 7 .O
22.8 29.7
18.4 29.4
.1
.4
.1
.3
9.8 40.0
9.8 50.3
10.0 30.5
6.9 6.0 19.6
6.9 21.9 15.7 5.4
6.9 4.8 9.4
1.O .9
1.o .9 .1
1 .o
2.75 10.2 22.7 .54
2.46 15.2 25.8 .5 1 .42
.6
2.0
12.6 1.0
Pellet binde8 .9 Vitamins A,D,Ee .I Chemical composition, DM basisf ME. Mcalkg 3.08 cp,% 14.4 ADF. W 17.8 Ca. % .54 P. 40 .50
1.o .9 .1
1.0 .9
.I
.9 .1
3.03 12.5 16.3 .56 .48
3.04 11.0 17.4 .49 .5 1
2.78 15.6 20.2 .59 A6
1.0
.I 2.78 12.4 22.9 .52 .4 3
34.3 39.2 .1 .7 2.1
LH
LM
72.5 .8 .1 3.9
76.8 .2 .8 17.1
LL 3.5 75.5
.I .9 11.1
3.1
6.9
1.o .9 .1
I .o .9 .I
2.45 13.0
2.47 12.2 26.6 .5 1 .47
21.2
.44
.9
.1
25.7 .53 .42
aAir-dry basis. bFirst letter in each treatment name designates energy level, and rhe second letter designates protein level: H, high; M, medium; L, low. ‘Contained (%) NaCI, 94 to95; Mn, > .20;ferrous iron, >.16; ferric iron, >.14; Cu, >.033; Zn.>.lo; I, >.007; Co, >.005. dLignosulfonatecompound. eContained2,200IU vitamin A, 2,200 IU vitamin D and .2 IU vitamin Wg. fFecal and urinary energy, CP,ADF, Ca and P were measured; methane energy was estimated.
were blocked by live BW, breed and sex and assigned randomly within block to one of nine dietary treatments. Diets contained either 2.46, 2.77 or 3.05 Mcal ME/kg DM and either 11.2, 12.7 or 15.1% CP; diets were fed in a 3 x 3 factorial arrangement in randomized complete blocks (Cochran and Cox, 1957). Each diet was mixed and pelleted to minimize differences in physical form and to prevent sorting by animals. Compositions of the nine experimental diets are presented in Table 1. All chemical compositions except ME were measured. Feed, urinary and fecal energy were measured, whereas methane energy was calculated from digestibility. Values of ME were calculated by difference. Dietary Ca and P concentrations among diets were similar. Before the experiment was begun, animals were fed a standard starter-grower diet (16.0% CP and 3.04 Mcal ME/kg DM) for 4 wk and were
dewormed with Amprolium3. Goats, housed in individual pens (61 x 122 cm2), had ad libitum access to their diet with 10% orts daily. Animals were allowed to exercise outside of their pens in a group for 3 h each day. Intake was measured daily and live weight was recorded immediately prior to addition of fresh feed on two consecutive days each week. Feed samples were taken weekly and subjected to chemical analyses. Live weight gain was calculated as the difference between initial and final live weights over specified intervals. Growth requirements were calculated both by the difference between intake and the calculated maintenance requirement (NRC, 1981) and by regressing growth rate on nutrient intake. The requirement (b, the slope) for growth considering maintenance alone was calculated as: ME intake, kcal/d = 101.38 BWkg,75 t b ADG,g/d
3Merck and Co., Rahway. NJ.
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Ingredient Corn Cottonseed hulls Limestone Dicalcium phosphate Soybean meal Dry molasses, Sugarcane Oats Alfalfa meal Cottonseed meal Trace mineralized
Treaunentb hlM ML
INTAKE AND GROWTH OF GOATS
CP intake, g/d = 4.15 BWkg.75 + b ADG, g/d
ME intake, kcal/d = 177.41 BWkg.75 + b’ ADG, gJd CP intake, g/d = 7.26 BW,,.75 + b’ ADG, g/d
Diet DM content was determined by ovendrying at 60°C for 48 h, GE with a Parr Adiabatic oxygen bomb calorimetefl, and N, Ca, P (AOAC, 1984) and ADF (Goering and Van Soest, 1970)) by standard procedures. Digestible energy and ME contents of experimental diets were determined in concurrent metabolism studies. Four animals per treatment were used in metabolism studies, which included a 14-d adjustment and a 7-d collection phase. Diets were fed twice daily, and water was available ad libitum. During the collection phase, feed supply was limited to the level of intake determined during the adjustment phase. Feed, fecal and urinary samples were collected daily. Digestibility of energy was 80.4, 71.8 and 64.2% for high-, medium- and low-energy diets, respectively. Urinary energy was determined on lyophilized samples. Methane energy loss was calculated according to Blaxter and Clappenon (1965) as: CH;1 (kcaV100 kcd feed) = 3.67 + .062 x energy digestibility (%).
Metabolizable energy (96) was calculated to be 71.9, 64.1 and 56.3% for high-, medium- and low-energy diets, respectively. The average ME to DE ratio in experimental diets (39) was higher than 32, which was used to calculate tabular values (NRC, 1981). This ratio resulted in higher ME values in experimental diets than those ME values calculated from tabular values. This higher ME to DE ratio is consistent with one previous report (Moe and Tyrrell, 1976). Data were subjected to ANOVA using the GLM procedure (SAS, 1979). Sources of
4Parr Instrument Co.. Moline, IL.
variation and corresponding error terms were energy, protein, energy x protein, sex, breed, block and residual. Energy and protein effects were determined by orthogonal contrasts when treatment effects were significant (Snedecor and Cochran, 1967). Regression analyses (SAS, 1979) were conducted to determine requirements for growth. Stepwise regression analysis aiming for maximal R improvement (SAS, 1979) was conducted to determine the factors affecting DMI and to develop prediction equations for DMI. Results and Discussion
Except for ME intake (Mcal/d or kcall ( k ~ . ~ ~ .and d ) )ME utilization for growth (kcal ME consumedg gain), interactions between energy and protein concentrations were not detected ( P > .05) for the parameters estimated. Dry matter intake was influenced by detary energy in a curvilinear fashion (Table 2). Values for wk 1 and wk 16 (final) for kids 17 and 32 wk of age are presented. During each growth interval observed, DMI expressed as gJd decreased as dietary energy density increased, This finding is in agreement with the principle that in ruminants, feed intake is regulated by dietary energy density. ME intake, rather than physical fill, appeared to be the dominant factor influencing DMI for our diets, all of which contained more than the low ME diet (2.46 Mcal ME/kg DM). However, ME intake would be expected to be similar among diets if the decrease in DMI with increasing energy density resulted from metabolic control of energy intake alone. Hence, the ME intake of goats fed the diet containing 3.05 Mcal MEkg DM suggests that additional factors might have been involved (Table 3). Because deposition of fat increased with dietary energy density in growing goats (Jindal et al.. 1980), feedback from adipose tissue might have contributed to the intake control (NRC, 1987). The curved response to Mcal MEkg suggests that intake could be controlled by gut fill when dietary energy density was below 2.46 Mcal MEkg DM. This assumption is based on the observation that change in DMI per unit change of ME was 400 @tal between diets of 2.46 and 2.77 Mcalkg versus 1,164 meal between diets of 2.77 and 3.05 Mcalkg; ME intake was similar in goats fed diets containing 2.46 and those fed 2.77 Mcal MEkg DM. Results derived from Garrett’s equation converting ME to NE (Garrett, 1980)
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Requirements (b’, the slope) for growth, considering expenditures for maintenance plus high activity, was calculated as:
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LU AND POTCHOIBA
TABLE 2. EFFECTS OF DIETARY ENERGY DENSITY AND PROTEIN LEVEL ON LIVE WEIGHT GAIN AND INTAKE Pa
Energy Itcm
Final W,I kg DMI, % BW 17b 32 DMI, g/kg 75 17 32 Live wt gain. g/d 17 10 20b 21 t o 2 4 25 to 28 29 IO 32 17 IO 32 DMI, g/d I7 lo 20 21 to24 25 to 28 29 10 32 17 to 32
Medium
30 19.6 325
30
High
L
Q
31.5
30 19.2 30.3
41 36
3.4 2.5
NS
4.1
***
NS
78.2 978
85.8 84.6
70.6
NS
**
18.Y
3.7
136 116 1w
127
104
98 113
119 109
115 933 1,142 1.259 1.336 1.168
902 1.028 1,103 1,143 1,044
S8.1
125 88 97 87 99
670 6%) 750 753 718
NS NS
***
NS NS
**
NS
NS
NS
NS NS
t NS NS NS
*
*
*** *** **n
*** ***
Low
r*
***
ap.level of significance; NS, p > .IO; +,P < .IO;*, P < .OS;
Pd
High
L
Q
SE
30 19.1 30.8
30 19.6 31.5
30 18.8 31.9
NS NS
NS NS
3.6 3.3
3.8 3.2
3.9 3.6
NS NS
NS
NS
.8 .7
75.1 77.9
78.6 76.3
81.0 86.4
NS I
NS NS
16.0 16.9
+
NS
46 46 50 53 26
122 105 97 94
*** ** *
Protein Medium
104
123 I08 108 86 106
142 110 106 109 I17
785 915 1,011 1,027 934
858 961 1,070 1,066 987
863 994 1 0 31 1.147 1.009
NS
NS NS t n
NS NS NS NS
2.6 4.5
*
KS
129
NS
144
NS
NS
*n
NS
193 163 131
*
NS
**, P < .OI;***, P < ,001;L, linear; Q, quadratic.
bAge of goal kids, wk.
indicate that 1.65 Mcal XE,,/kg would be the energy level with maximal feed intake. This value is considerably lower than 1.8 to 1.9 Mcal NE,/kg for cattle and for sheep (NRC, 1987). Compared with cattle and sheep grazing one range pasture, faster turnover rate and shorter retention time in the digestive tract were observed in goats (Huston et al., 1986). Ruminal turnover rate and total mean retention time was 5.5%/h and 31.5 h, respectively, in goats fed alfalfa hay (Lu et al., 1980). Perhaps control of intake by gut fill is species-specific. Dry matter intake was influenced by dietary CP level in a linear fashion (Table 2). Except during wk 25 to 28, intake increased as dietary CP level increased. Increases i n DMI per gram increase in CP was 35 g/g between 11.2 and 12.7% CP versus 9 g/g between 12.7 and 15.1% CP. Average live weight gain was not influenced by dietary energy density in any growth interval except during wk 21 to 24 and wk 17 to 32 (Table 2). Average live weight gain was related negatively to dietary energy density during wk 17 to 32. This finding is attributed to the inverse relationship between DMI and dietary energy density. In this study, intake of' ME was lower for the diet containing 3.05
Mcal ME/kg DM. Jindal et al. (1980) observed that growth rate (g/d) of Alpine x Beetal goats decreased from 109 to 68 when dietary energy density was increased from 78 to 86% TDN. Average ME intake (Mcal/d) was 2.93, 2.98 and 2.24 for diets of 2.46, 2.77 and 3.05 Mcal/ kg ME, respectively. These values correspond with growth rates of 115, 113 and 99 g/d for these respective dietary energy densities. Although composition of weight gain was not determined in this study, one might speculate that the highest energy diet resulted in greater fat deposition in tissue. Body fat of growing goats increased from 16 to 27% when dietary energy density was increased by 29% {Jindal et al., 1980). Energetic efficiencies for live weight gain (Mcal ME intake/g of gain) were similar between low-energy (.025) and highenergy (.023) diets. Because of larger gut fill as a result of ingesting the low-energy diet, one would expect that the efficiency of empty BW gain was higher for goats fed the highenergy diet. Average diiily gain increased as dietary protein level increased during wk 17 to 32 of age. Because DMI was related positively to dietary CP level, increased ADG could be explained as a response to increased protein intake. However, the increased ADG during
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Number lni~ialwt, kg
Low
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INTAKE AND GROWTH OF GOATS TABLE 3. FACTORS AFFECTING ME AND CP INTAKE ME intake Item
McaI/da
k~aI/(kg.~’.d)~
g/d‘
g/(kg75.d)d
30 30 30
2.93 2.98 2.24
248 260 198
181
13.4 11.5 8.1
30 30 30
2.61 2.66 2.89
228 228 250
125 153
36 54
2.81 2.65
2 34 236
132 125
10.9
45 45
2.86 2.57 .37
242 229
134 121 18
11.3
145 9l
Protein LOW MCdllUll
Iiigh Sex
Male casu-ales Female Breed Alpine Nubian SE
21
105
9.1 10.7
13.2 11.1
10.7
2.4
aEnergy:linear and quadratic. P < ,001; protein: linear, P < .01; quadratic. P > .IO; sex, P < .05; breed, P c .001. bEnergy: linear and quadratic, P < .001; protein: linear, P < ,001; quadratic, P < .05; sex, P > .lo; breed, P< .01. ‘Energy: 1inear.P < .0001, quadratic, P < .IO; protein: linear, P < .W1. quadratic, P > .IO; sex, P < .IO. breed, P < ,001. dEnergy: linear, P < .001. quadratic. P < .01; protein: linear, P < .001. quadratic, P < .05; sex, P > .IO; breed, P c .01.
the entire experimental period was attributed largely to the increase in ADG between 17 and 20 wk of age. This implies that growing goats responded to dietary protein concentration only at younger ages. In addition to dietary energy density and CP level, breed and sex influenced DMI by growing goats (Table 4). Except during 29 to 32 wk of age, DMI was higher ( P < .01) in Alpine goats than in Nubian goats in all growth intervals observed. However, no difference was observed in ADG between these breeds. Dry matter intake was higher for male castrate kids than for female kids during intervals of 21 to 24 ( P < .lo), 29 to 32 ( P < .01) and 17 to 32 wk (P < .05) of age. Average daily gain was not different ( P > .lo) between male castrates and females in any growth interval. Factors affecting ME and CP intakes are presented in Table 3. Intake of ME (Mcal/d and k ~ a l / ( k g . ~ ~ .was d ) ) affected curvilinearly ( P < .001) by dietary energy density. Intake of ME (Mcal/d) was affected linearly ( P < .01) by dietary protein level, and ME intake (kcal/ ( k ~ . ~ ~ -was d ) )affected curvilinearly (linear, P < ,001; quadratic, P < .05) by dietary protein concentration. The effects of dietary energy and protein concentrations on energy intake were consistent with their effect on DMI. Because sex affected ME intake, expressed as Mcal/d but not as kcal/(kg75.d), the effect of
sex on ME intake can be attributed to body size differences between male castrates and females. Breed influenced ME intake expressed either as Mcal/d or as k ~ a l / ( k g . ~ ~A .d). confounding effect of dietary energy density on CP intake was observed. The decrease in CP intake as a result of ar~increase in dietary energy density contributed to the negative effect of dietary energy density on DMI. Protein levels may not have been adequate for maximal growth rate in the high-energy, lowprotein diet. This is evidenced by the effects of interaction of energy and protein concentrations on ME intake (Mcal/d, P < .05; kcal/ kg.75.d, P < .01) and on ME utilization for growth (kcal ME consumed/g gain, P < .001). Goats fed the high-energy, low-protein diet had lower ME intakes (1.90 Mcal/d or 155 k ~ a l / ( k g . ~ ~ .and d ) ) ME utilization for growth (6.1 kcal ME consumed d/g gain) compared with treatment means of goats fed the other eight diets. Average daily gain for the 16-wk period was 88, 97 and 113 g/d for the high-energy diet with low-, medium- and highprotein levels, respectively. This trend was similar for all growth intervals observed. However, the interaction of energy and protein concentrations on ADG was not significant. The effect of sex on protein intake was largely due to body size differences, as observed for ME intake. Breed affected CP intake independently of body size.
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Energy Low Medium
CP intake
No.
1756
LU AND POTCHOLBA TABLE 4. EFFECT OF BREED AND SEX ON LlVE WEIGHT GAlN AND INTAKE Breed
Item
45
45
133 104 100 91 107
127 111 106 101 111
895 1,016
775 897 978 1,053 926
1
.ow
1,102 1,028
Sex
Nubian
Male castrates
54
36
NS NS NS NS NS
130 105
128 111
1W
102 110
*** ** **
823 935 1,016 1,041 954
853 989 1,070 1,132 1,011
**
Pa
NS NS NS NS NS
97
107 92
NS
aP, level of significance; NS, P > .10 ', P < .lo; *, P < .05; **, P < .01; bAge of goat kids, wk
Estimates of ME and CP utilization for growth above maintenance are given in Table 5. Dietary energy density affected energy utilization for growth curvilinearly and for protein utilization linearly ( P < .001). Dietary protein level affected protein but not energy utilization for growth. No effect of sex on energy and protein utilization for growth was detected. However, Nubian kids appeared to be more efficient in energy and protein utilization for growth, as evidenced by lower kcal ME and g CP for each gram of gain (P < .OOl>. Nubian goats in general have a greater mature size than Alpine goats. The effect of dietary energy density on energy utilization for gain could be attributed to differences in gut fill and composition of gain, as discussed previously. Effect of dietary energy density on utilization of protein for gain could be attributed to the energy to protein ratio. The highest concentrate diet may have enhanced microbial incorporation of NH3, which in turn contributed to a higher non-ammonia N flow in the duodenum. The effect of dietary protein level on protein utilization for gain could be explained by an excess of CP and loss of ammonia N in the urine. Such diminishing returns are observed commonly in growing and lactating ruminants. Presumably the Nubian is more efficient in BW gain but less efficient in milk production than is the Alpine goat. Alpine goats produced more milk than the Nubian when dietary, physiological and environmental conditions were similar (Lu et al., 1987). When monthly ME intake was regressed on live weight gain, the slope was 4.60 kcal ME/g
Female
Pa
NS i
NS
** *
***, P < ,001.
of gain (Figure 1). This value was much lower than the recommended value (NRC, 1981). However, the recommended value, 7.25 kcal ME/g of gain, is the mean of three separate observations, 10.18, 5.14 and 6.43 kcal ME/g of g&n, observed from indigenous Malaysian, West African Dwarf and various breeds of Indian goats. The SE for the ME requirement indicated a 95% confidence interval between 3.3 and 5.9 kcal/g of gain, which is slightly to
TABLE 5 . FACTORS AFFECTING UTILIZATION OF ME AND CP FOR GROWTH ABOVE MAlNTENANCE
hem
Energy Low Medium High Protein Low Medium High Sex Male castrates Female
No.
kcal ME g C P consumed/ consumed/ g gaina g gainb
30 30 30
13.0 14.0 8.7
.97
30 30 30
11.4 11.8 12.6
.55
36 54
12.0 11.8
.74 .73
45 45
13.1 10.7 2.5
,615 .15
.77 .47 .74 .92
Breed
Alpine Nubian SE
.%I
aEnergy: linear and quadratic, P < ,001; protein: linear and quadratic, P > .lo; sex, P > .IO; breed, P < .001. bEnergy: linear, P < .001, quadratic, P > .IO;protein: linear, P < ,001, quadratic, P > .IO; sex, P > .lo; breed, P < ,001.
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h'umber Live wt gain, g/d 17 to 20b 21 to 24 25 to 28 29 to 32 17 to 32 DMI. g/d 17 to 20 21 to24 25 to 28 29 to 32 17 to 32
Alpine
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INTAKE AND GROWTH OF GOATS
4 4
M
200 -
Y = 2216 (+79)t 4 60 i+ 65iX
500
r = 35
S ~ =X627 p' 0001 n = 360 (48 hidden)
M M
M
'
39003 600
L
I
1
M LML M
m
1
M
M L
i
u
I
-
2 3300L1
3000
-
2 700
-
2 400
-
2 100
-
800
-
1.500
-
w
1
1,200
M
"
#
H
L
M H
M H
n "
H
Y
H
"
H
L H HL M LH H H
i
L
M h H
...
.
n n
n
HM
M
k"
"H
L "
I
1
h
H
M
H
I
l
I
1
I
,
,
I
,
I
,
I
I
I
,
I
I
,
,
substantially lower than all of the values used (Table 6). Requirement values derived from by NRC (1981). When monthly live weight regression and empirical approaches tended to gain was regressed on CP intake, the slope was be lower during 17 to 20 wk of age than at .26 g CP/g of gain (Figure 2). The recom- other intervals. This is attributed to differences mended value (NRC, 1981), .28 g CP or .20 g in composition of gain as discussed previously. DP/g of gain, is the mean of .27, .14 and .17 g The protein-to-fat ratio of gain decreases as DP/g of gain observed for non-dairy breeds. age of ruminants increases. Y intercept values, Different regression equations were derived 2,216 kcal ME and 99 g CP, were equivalent when the requirements were adjusted for BW to values for maintenance plus high activity differences. The equation for the energy recommended by NRC (1981). This implies requirement is y = 197 (f5)+ .35 (k .04)x, r = that goats require substantial amounts of ME .40, where y is ME intake (k~al/(BWk,.~~.d)) and CP for activity during 4 to 8 mo of age. and x is rowth rate (g/d). The intercept, 197 Although kids were housed in individual pens, ) , size of pens was large enough to allow k ~ a l / ( k g Sd), . ~ is larger than 101 k ~ a l / ( k g ~ ~ . dthe which was used to calculate maintenance active exercise. Compared with calves and requirement by M C (1981). This implies that lambs, kids were extremely active in jumping additional energy might have been needed for and moving both in and out of pens. When the activity. The equation for the protein require- growth requirements considering high activity ment is y = 8.78 (f.37) + .02 (f.OO)x, r = .33, ( 3 5 x maintenance) are calculated using the where y is CP intake (g/(BWkg.75-d))and x is empirical approach, the difference between regression and empirical approaches was regrowth rate (g/d). When energy and protein requirements per duced (Table 6). Regardless of sex and breed, three facunit of weight gain were derived from regression analysis, values were much smaller than tors-dietary DE, live BW and ADG-were the those derived from the empirical approach best variables to predict DMI of growing kids,
s
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M
1758 275
250
LU AND POTCHOIBA
,
Y
=
I =
99 (55) + 2612 0 4 ) X
40
Syx=408 p c 0007 n = 360 (36 hidden)
b
M
i
200
-
D 0,
w Y
2
175
z_
," +
B
150
'$
125
t
7
a
0
100
75
5c I
I
I
100
80
I
60
I
40
1
1
1
1
1
20
0
20
40
60
1
80
1
100
1
120
1
140
1
160
1
180
1
200
1
1
1
1
220 240
1
260
280
300
LIVE WEIGHT GAIN g d
Figure 2 The relauonship betueen monthly CP make and live weight gam in Alpme and Nubian goats fed high (H)-, medium (M)and low (L)-protem diets
except for goats 29 to 32 wk of age (Table 7). Dietary ADF substituted for dietary DE to best estimate DMI of goats during 29 to 32 wk of age. In addition to dietary DE, live BW and AM;, the independent variables tested in stepwise regression analysis were dietary CP and ADF concenmations. Although dietary CP affected DMl (Table 2), it was not among the best three variables to predict DMI in growing
goats. Dietary ADF, live BW and ADG were the best three variables to predict DMI of Nubian and of female goats 17 to 32 wk of age. The R2 for intake increased from .58 to .76 as the age of kids increased from 17 to 32 wk. The R2 for intake of all kids from 17 to 32 wk of age was .73 with a Sy.x equal to 13% of the mean. A slight improvement in R' was detected when separate prediction equations
TABLE 6. METABOLIZABLE ENERGY AND CF' REQUIREMENTS FOR GROWTHa kcal ME& gain Age, wk
Regression
Maintenance Maintenance + onlyb activityC
17 to 20 21 10 24 25 to 28 29 to 32 17 to 32
4.6 5.7 7.1 6.9 4.6
9.3 14.3 12.8 15.6 11.9
aN = 90.
bME or CP = aW.75 + b (ADG). 'ME or CP = 1.75 aW.75 + b (ADG).
4.8
I .9 7.2 9.3 5.9
Regression
g CP/g gain Maintenance Maintenance + onlyb activity'
.32 .33 .34 .36 .26
.57 .9 1 .80 .96 .74
30 .54
.47 .57 .39
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225
1759
IhTAKE AND GROWTH OF GOATS
TABLE 7. PREDICTION EQUATIONS FOR DMI OF GROWING GOATS AT VARIOUS GROWING PERIODS ~~
171032
Class
Breed Alpine Nubian Sex Male castrates Female
~~~
Equation Yab = 1042.2 - 2973x1 + 254x2 + 1 . 7 ~ 3 Y = 16.11 -466.9~1+ 28.3X2 + 1 . 2 ~ 3 Y = 1966.7 - 590.7X1 + 2 9 . 1 ~ 2+ 1.4X3 Y =-901.6+5482.5x4+23.4x2+ l.lx3 Y = 1748.7 - 4 9 5 . 7 ~+~ 1 8 . 4 +~ 3~. 0 ~ 3
No. 90
r2
%.x
p
.58
123
90
152
90 90 90
.64 .68 .76 .73
I67 154
,000 1 ,000 1 .000 1 .0001 ,000I
Y = 1804-487.5~1+ 13.6X2+3.8~3 Y = 4 9 1 + 4128x4 + 1 6 . 7 ~ + 2 2.9~3
45 45
.78 .?5
117 118
.ooo1
Y = 1301 - 356.2~1+ 1551x4 + 47x3
36 54
.70
141 117
,0001
Y =-726 + 3891x4 + 2 6 . 7 ~ 2+ 1.7X3
.77
127
.om1 ,0001
a Y , DMl (g/d); X I . dietary DE (Kcal/g); x2. BW (kg); x3, ADG (g/d); x4. dietary ADF (8). bBased on the best three variables model lound.
were developed for Alpine. Nubian and female kids. Implications
The estimated energy requirement for growth determined by regression was 33% lower than current (1981) NRC recommendations. The overestimation presumably resulted from underestimating energy needs for activity. The protein requirement for growth was 7% lower than current NRC (1981) recommendations. Prediction equations considering BW, growth rate, sex, breed and dietary energy density allowed estimation of DMI of growing goats. Differences between goat breeds in efficiencies of ME and CP utilization for gain suggest that mature weight (Nubian > Alpine) should be considered when nutrient requirements are estimated. Literature Cited AOAC. 1984. Official Methods of Analysis (13th Ed.). Association of Official Analytical Chemisb. Washington. DC. Akinsoyinu, A. 0. 1974. Studies on protein and energy utilization by the West African dwarf goats. Ph. D. Dissertation. University of Ibadan. Nigeria. Blaxier. K. L. and J . L. Clapperton. 1965. Prediction of the amount of rnelhane produced by ruminants. Br. J. Nutr. 19:511.
Cochran. W. G. and G. W.Cox. 1957. Experimental Designs (2nd Ed.). John Wiley. New York. Devendra. C. 1967. Studies in the nutrition of h e indigenous goat of Malaysia. 11. The requirements of live weight gain. Malays. Agnc. J . 46:98.
Garrett. W. N. 1980. Energy utilization of growing cattle as determined in 72 comparative slaughter experiments. In: L. E. Mount (Ed.) Energy Metabolism. pp 3-7. Buttenvonhs, London, U K . Goering. H. K.. and P. J. Van Soest. 1970. Forage fiber analyses (apparatus, reagents, procedures, and some applications). Agnc. Handbook 379, ARS, USDA, Washington, DC. Huston, J . E., B. S. Rector. W. C. Ellis and M. L. Allen. 1986. Dynamics of digestion in cattle. sheep, goats and deer. J . Anim. Sci. 62208. Jindal, S. K., A. K. Mehta and M.V.N. Rao. 1980. Influence of dietary energy on the body composition and feed conversion efficiency during growth in goats. Indian J. Nutr. Dirt. 17:95. Lu, C. D., N. A. Jorgensen and G. P. Barrington. 1980. Intake, digestibility and rate of passage of silages and hays from wet fractionation of alfalfa. J. Dairy Sci. 63: 2051. Lu, C. D., T. Sahlu and J. M. Fernandez. 1987. Assessment of energy and protein requirements for growth and lactation in goats. h o c . 1V Int. Conf. on Goats 2:1229. Moe. P. W. and H. F. Tyrrell. 1976. Estimating metabohable and net energy of feeds. Prcc. 1st hi. Symp. on Feed Composition, Animal Nutrient Requirements. and Compuierization, Feedstuffs lnst.. Logan, UT. NRC. 1978. Nutrient Requirements of Dairy Catlle (5th Ed.). National Academy Press, Washington, DC. NRC. 1981. Nutnent Requirements of Goats. National Academy Press, Washinyon, DC. NRC. 1985. Nutrient Requirements of Sheep (6th Ed.). National Academy Press, Washington, DC. NRC. 1987. Predicting feed intake of food-producing animals. National Academy Press, Washington, DC. Rajpoot, R. L. 1979. Energy and protein in goat nutnilon. Ph.D. Dissenation. Raja Balwant Singh College. Bichpuri (Agra), India. Snedecor, G. W. and W. G. Cochran. 1967. Statistical Methods (6th Ed.). Iowa State Univ. Press, Ames. SAS. 1979. SAS User’s Guide: Statistics. SAS Inst.. Inc.. Cary, NC.
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Age, wk 17 to 20 21 10 26 25 to 28 29 10 32 17 to 32 171032
Langston University2, Langston, OK 73050 ABSTRACT
Growing goats, 45 Alpine and 45 Nubian, were used in a 3 x 3 factorial arrangement to quantify the influence of dietary energy and protein levels on daily DM intake and nument utilization for growth. Goats had ad libitum access to complete mixed diets containing either 2.46, 2.77 or 3.05 McaI/kg ME plus 11.2, 12.7 or 15.1% CP for 16 wk. Dry matter intake decreased curvilinearly as dietary ME density increased (P < .001). Dry matter intake increased linearly ( P < .OS) as dietary CP level increased during all growth intervals except wk 25 to 28 of age. Average daily gain was 115, 113 and 99 g/d for goats fed diets containing 2.46, 2.77 and 3.05 Mcal/kg ME, respectively. Average daily gain was 104, 106 and 117 g/d for goats fed diets with 11.2, 12.7 and 15.1% CP, respectively. Dry matter intake was higher (P < .01) for Alpine than for Nubian goats, whereas ADG was similar between breeds. Intake of ME was 248, 260 and 198 k ~ a l / ( k g . ~ ~for . d )goats fed the lowmedium- and high-energy diets, respectively. Intake of CP was 9.1, 10.7 and 13.2 g/ (kg 75.d) for goats fed low-, medium- and high-protein diets, respectively. Average requirements for growth derived from regression analysis of all data points were 4.6 kcal ME and .26 g CP/g ADG. The prediction equation for intake of growing goats of 4 to 8 mo of age was: DMI, g/d = 1,749 - 496 DE, kcal/g + 18 live weight, kg + 3 ADG, g/d; r2 = .73 (Sy.x = 127, P < .OOO1,n = 90). The requirement of ME for growth was 33% lower than the value recommended in 1981 by the National Research Council. (Key Words: Goats, Growth, Intake, Energy, Protein.) J. h i m . Sci. 1990. 68:1751-1759
(NRC, 1978, 1985). The protein requirement for goats is the mean of ,274, .139 and .173 g The National Research Council indicated digestible protein (DP)/g of gain based on that 7.25 kcal ME and .284 g CP were required calorie-to-protein ratios (Devendra, 1967; per gram of gain by goats (NRC, 1981). This Akinsoyinu, 1974 Rajpoot, 1979). Because of requirement is the mean of 10.18, 5.14, and the relatively small number of observations in 6.43 kcal ME/g of gain derived from experi- these three studies and the difference in intake ments that utilized indigenous Malaysian and growth rate between goats produced in goats, West African dwarf goats and various tropical versus temperate zones, protein rebreeds of Indian goats, respectively (Devendra, quirements for growth need further evaluation. 1967; Akinsoyinu, 1974; Rajpoot, 1979). This This study 1) investigated the effect of dietary mean ME requirement, with a coefficient of energy and protein concentrations on utilizavariation of 36%, is considerably greater than tion of nutrients for growth, 2) estimated DMI the requirements for dauy cattle and sheep, in growing goats and 3) estimated energy and 2.90 and 3.32 kcal ME/g of gain, respectively protein requirements of growing goats. Introduction
Materialsand Methods €XI.
'Scientific Paper Number OKLP-107,A&. hog. 2 ~ Inst.. for Goat RCS. Received May 30.1989. Accepted October 22.1989.
Res. and
Ninety growing goats, 45 Alpine and 45 Nubian, 18 male castrates and 27 female of each breed, were used in a 16-wk continuousfeeding experiment. Animals (16 wk of age)
1751
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C. D. Lu and M. J. Potchoiba
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LU AND POTCHOIBA
TABLE 1. COMPOSITIONa OF DIETS FED TO GOATS ~
~~
Item
saltc
HH
HM
HL
MH
34.4 3.8 .7 .I 9.4
34.3 .9 .7
49.7 7 .O
22.8 29.7
18.4 29.4
.1
.4
.1
.3
9.8 40.0
9.8 50.3
10.0 30.5
6.9 6.0 19.6
6.9 21.9 15.7 5.4
6.9 4.8 9.4
1.O .9
1.o .9 .1
1 .o
2.75 10.2 22.7 .54
2.46 15.2 25.8 .5 1 .42
.6
2.0
12.6 1.0
Pellet binde8 .9 Vitamins A,D,Ee .I Chemical composition, DM basisf ME. Mcalkg 3.08 cp,% 14.4 ADF. W 17.8 Ca. % .54 P. 40 .50
1.o .9 .1
1.0 .9
.I
.9 .1
3.03 12.5 16.3 .56 .48
3.04 11.0 17.4 .49 .5 1
2.78 15.6 20.2 .59 A6
1.0
.I 2.78 12.4 22.9 .52 .4 3
34.3 39.2 .1 .7 2.1
LH
LM
72.5 .8 .1 3.9
76.8 .2 .8 17.1
LL 3.5 75.5
.I .9 11.1
3.1
6.9
1.o .9 .1
I .o .9 .I
2.45 13.0
2.47 12.2 26.6 .5 1 .47
21.2
.44
.9
.1
25.7 .53 .42
aAir-dry basis. bFirst letter in each treatment name designates energy level, and rhe second letter designates protein level: H, high; M, medium; L, low. ‘Contained (%) NaCI, 94 to95; Mn, > .20;ferrous iron, >.16; ferric iron, >.14; Cu, >.033; Zn.>.lo; I, >.007; Co, >.005. dLignosulfonatecompound. eContained2,200IU vitamin A, 2,200 IU vitamin D and .2 IU vitamin Wg. fFecal and urinary energy, CP,ADF, Ca and P were measured; methane energy was estimated.
were blocked by live BW, breed and sex and assigned randomly within block to one of nine dietary treatments. Diets contained either 2.46, 2.77 or 3.05 Mcal ME/kg DM and either 11.2, 12.7 or 15.1% CP; diets were fed in a 3 x 3 factorial arrangement in randomized complete blocks (Cochran and Cox, 1957). Each diet was mixed and pelleted to minimize differences in physical form and to prevent sorting by animals. Compositions of the nine experimental diets are presented in Table 1. All chemical compositions except ME were measured. Feed, urinary and fecal energy were measured, whereas methane energy was calculated from digestibility. Values of ME were calculated by difference. Dietary Ca and P concentrations among diets were similar. Before the experiment was begun, animals were fed a standard starter-grower diet (16.0% CP and 3.04 Mcal ME/kg DM) for 4 wk and were
dewormed with Amprolium3. Goats, housed in individual pens (61 x 122 cm2), had ad libitum access to their diet with 10% orts daily. Animals were allowed to exercise outside of their pens in a group for 3 h each day. Intake was measured daily and live weight was recorded immediately prior to addition of fresh feed on two consecutive days each week. Feed samples were taken weekly and subjected to chemical analyses. Live weight gain was calculated as the difference between initial and final live weights over specified intervals. Growth requirements were calculated both by the difference between intake and the calculated maintenance requirement (NRC, 1981) and by regressing growth rate on nutrient intake. The requirement (b, the slope) for growth considering maintenance alone was calculated as: ME intake, kcal/d = 101.38 BWkg,75 t b ADG,g/d
3Merck and Co., Rahway. NJ.
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Ingredient Corn Cottonseed hulls Limestone Dicalcium phosphate Soybean meal Dry molasses, Sugarcane Oats Alfalfa meal Cottonseed meal Trace mineralized
Treaunentb hlM ML
INTAKE AND GROWTH OF GOATS
CP intake, g/d = 4.15 BWkg.75 + b ADG, g/d
ME intake, kcal/d = 177.41 BWkg.75 + b’ ADG, gJd CP intake, g/d = 7.26 BW,,.75 + b’ ADG, g/d
Diet DM content was determined by ovendrying at 60°C for 48 h, GE with a Parr Adiabatic oxygen bomb calorimetefl, and N, Ca, P (AOAC, 1984) and ADF (Goering and Van Soest, 1970)) by standard procedures. Digestible energy and ME contents of experimental diets were determined in concurrent metabolism studies. Four animals per treatment were used in metabolism studies, which included a 14-d adjustment and a 7-d collection phase. Diets were fed twice daily, and water was available ad libitum. During the collection phase, feed supply was limited to the level of intake determined during the adjustment phase. Feed, fecal and urinary samples were collected daily. Digestibility of energy was 80.4, 71.8 and 64.2% for high-, medium- and low-energy diets, respectively. Urinary energy was determined on lyophilized samples. Methane energy loss was calculated according to Blaxter and Clappenon (1965) as: CH;1 (kcaV100 kcd feed) = 3.67 + .062 x energy digestibility (%).
Metabolizable energy (96) was calculated to be 71.9, 64.1 and 56.3% for high-, medium- and low-energy diets, respectively. The average ME to DE ratio in experimental diets (39) was higher than 32, which was used to calculate tabular values (NRC, 1981). This ratio resulted in higher ME values in experimental diets than those ME values calculated from tabular values. This higher ME to DE ratio is consistent with one previous report (Moe and Tyrrell, 1976). Data were subjected to ANOVA using the GLM procedure (SAS, 1979). Sources of
4Parr Instrument Co.. Moline, IL.
variation and corresponding error terms were energy, protein, energy x protein, sex, breed, block and residual. Energy and protein effects were determined by orthogonal contrasts when treatment effects were significant (Snedecor and Cochran, 1967). Regression analyses (SAS, 1979) were conducted to determine requirements for growth. Stepwise regression analysis aiming for maximal R improvement (SAS, 1979) was conducted to determine the factors affecting DMI and to develop prediction equations for DMI. Results and Discussion
Except for ME intake (Mcal/d or kcall ( k ~ . ~ ~ .and d ) )ME utilization for growth (kcal ME consumedg gain), interactions between energy and protein concentrations were not detected ( P > .05) for the parameters estimated. Dry matter intake was influenced by detary energy in a curvilinear fashion (Table 2). Values for wk 1 and wk 16 (final) for kids 17 and 32 wk of age are presented. During each growth interval observed, DMI expressed as gJd decreased as dietary energy density increased, This finding is in agreement with the principle that in ruminants, feed intake is regulated by dietary energy density. ME intake, rather than physical fill, appeared to be the dominant factor influencing DMI for our diets, all of which contained more than the low ME diet (2.46 Mcal ME/kg DM). However, ME intake would be expected to be similar among diets if the decrease in DMI with increasing energy density resulted from metabolic control of energy intake alone. Hence, the ME intake of goats fed the diet containing 3.05 Mcal MEkg DM suggests that additional factors might have been involved (Table 3). Because deposition of fat increased with dietary energy density in growing goats (Jindal et al.. 1980), feedback from adipose tissue might have contributed to the intake control (NRC, 1987). The curved response to Mcal MEkg suggests that intake could be controlled by gut fill when dietary energy density was below 2.46 Mcal MEkg DM. This assumption is based on the observation that change in DMI per unit change of ME was 400 @tal between diets of 2.46 and 2.77 Mcalkg versus 1,164 meal between diets of 2.77 and 3.05 Mcalkg; ME intake was similar in goats fed diets containing 2.46 and those fed 2.77 Mcal MEkg DM. Results derived from Garrett’s equation converting ME to NE (Garrett, 1980)
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Requirements (b’, the slope) for growth, considering expenditures for maintenance plus high activity, was calculated as:
1753
1754
LU AND POTCHOIBA
TABLE 2. EFFECTS OF DIETARY ENERGY DENSITY AND PROTEIN LEVEL ON LIVE WEIGHT GAIN AND INTAKE Pa
Energy Itcm
Final W,I kg DMI, % BW 17b 32 DMI, g/kg 75 17 32 Live wt gain. g/d 17 10 20b 21 t o 2 4 25 to 28 29 IO 32 17 IO 32 DMI, g/d I7 lo 20 21 to24 25 to 28 29 10 32 17 to 32
Medium
30 19.6 325
30
High
L
Q
31.5
30 19.2 30.3
41 36
3.4 2.5
NS
4.1
***
NS
78.2 978
85.8 84.6
70.6
NS
**
18.Y
3.7
136 116 1w
127
104
98 113
119 109
115 933 1,142 1.259 1.336 1.168
902 1.028 1,103 1,143 1,044
S8.1
125 88 97 87 99
670 6%) 750 753 718
NS NS
***
NS NS
**
NS
NS
NS
NS NS
t NS NS NS
*
*
*** *** **n
*** ***
Low
r*
***
ap.level of significance; NS, p > .IO; +,P < .IO;*, P < .OS;
Pd
High
L
Q
SE
30 19.1 30.8
30 19.6 31.5
30 18.8 31.9
NS NS
NS NS
3.6 3.3
3.8 3.2
3.9 3.6
NS NS
NS
NS
.8 .7
75.1 77.9
78.6 76.3
81.0 86.4
NS I
NS NS
16.0 16.9
+
NS
46 46 50 53 26
122 105 97 94
*** ** *
Protein Medium
104
123 I08 108 86 106
142 110 106 109 I17
785 915 1,011 1,027 934
858 961 1,070 1,066 987
863 994 1 0 31 1.147 1.009
NS
NS NS t n
NS NS NS NS
2.6 4.5
*
KS
129
NS
144
NS
NS
*n
NS
193 163 131
*
NS
**, P < .OI;***, P < ,001;L, linear; Q, quadratic.
bAge of goal kids, wk.
indicate that 1.65 Mcal XE,,/kg would be the energy level with maximal feed intake. This value is considerably lower than 1.8 to 1.9 Mcal NE,/kg for cattle and for sheep (NRC, 1987). Compared with cattle and sheep grazing one range pasture, faster turnover rate and shorter retention time in the digestive tract were observed in goats (Huston et al., 1986). Ruminal turnover rate and total mean retention time was 5.5%/h and 31.5 h, respectively, in goats fed alfalfa hay (Lu et al., 1980). Perhaps control of intake by gut fill is species-specific. Dry matter intake was influenced by dietary CP level in a linear fashion (Table 2). Except during wk 25 to 28, intake increased as dietary CP level increased. Increases i n DMI per gram increase in CP was 35 g/g between 11.2 and 12.7% CP versus 9 g/g between 12.7 and 15.1% CP. Average live weight gain was not influenced by dietary energy density in any growth interval except during wk 21 to 24 and wk 17 to 32 (Table 2). Average live weight gain was related negatively to dietary energy density during wk 17 to 32. This finding is attributed to the inverse relationship between DMI and dietary energy density. In this study, intake of' ME was lower for the diet containing 3.05
Mcal ME/kg DM. Jindal et al. (1980) observed that growth rate (g/d) of Alpine x Beetal goats decreased from 109 to 68 when dietary energy density was increased from 78 to 86% TDN. Average ME intake (Mcal/d) was 2.93, 2.98 and 2.24 for diets of 2.46, 2.77 and 3.05 Mcal/ kg ME, respectively. These values correspond with growth rates of 115, 113 and 99 g/d for these respective dietary energy densities. Although composition of weight gain was not determined in this study, one might speculate that the highest energy diet resulted in greater fat deposition in tissue. Body fat of growing goats increased from 16 to 27% when dietary energy density was increased by 29% {Jindal et al., 1980). Energetic efficiencies for live weight gain (Mcal ME intake/g of gain) were similar between low-energy (.025) and highenergy (.023) diets. Because of larger gut fill as a result of ingesting the low-energy diet, one would expect that the efficiency of empty BW gain was higher for goats fed the highenergy diet. Average diiily gain increased as dietary protein level increased during wk 17 to 32 of age. Because DMI was related positively to dietary CP level, increased ADG could be explained as a response to increased protein intake. However, the increased ADG during
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Number lni~ialwt, kg
Low
1755
INTAKE AND GROWTH OF GOATS TABLE 3. FACTORS AFFECTING ME AND CP INTAKE ME intake Item
McaI/da
k~aI/(kg.~’.d)~
g/d‘
g/(kg75.d)d
30 30 30
2.93 2.98 2.24
248 260 198
181
13.4 11.5 8.1
30 30 30
2.61 2.66 2.89
228 228 250
125 153
36 54
2.81 2.65
2 34 236
132 125
10.9
45 45
2.86 2.57 .37
242 229
134 121 18
11.3
145 9l
Protein LOW MCdllUll
Iiigh Sex
Male casu-ales Female Breed Alpine Nubian SE
21
105
9.1 10.7
13.2 11.1
10.7
2.4
aEnergy:linear and quadratic. P < ,001; protein: linear, P < .01; quadratic. P > .IO; sex, P < .05; breed, P c .001. bEnergy: linear and quadratic, P < .001; protein: linear, P < ,001; quadratic, P < .05; sex, P > .lo; breed, P< .01. ‘Energy: 1inear.P < .0001, quadratic, P < .IO; protein: linear, P < .W1. quadratic, P > .IO; sex, P < .IO. breed, P < ,001. dEnergy: linear, P < .001. quadratic. P < .01; protein: linear, P < .001. quadratic, P < .05; sex, P > .IO; breed, P c .01.
the entire experimental period was attributed largely to the increase in ADG between 17 and 20 wk of age. This implies that growing goats responded to dietary protein concentration only at younger ages. In addition to dietary energy density and CP level, breed and sex influenced DMI by growing goats (Table 4). Except during 29 to 32 wk of age, DMI was higher ( P < .01) in Alpine goats than in Nubian goats in all growth intervals observed. However, no difference was observed in ADG between these breeds. Dry matter intake was higher for male castrate kids than for female kids during intervals of 21 to 24 ( P < .lo), 29 to 32 ( P < .01) and 17 to 32 wk (P < .05) of age. Average daily gain was not different ( P > .lo) between male castrates and females in any growth interval. Factors affecting ME and CP intakes are presented in Table 3. Intake of ME (Mcal/d and k ~ a l / ( k g . ~ ~ .was d ) ) affected curvilinearly ( P < .001) by dietary energy density. Intake of ME (Mcal/d) was affected linearly ( P < .01) by dietary protein level, and ME intake (kcal/ ( k ~ . ~ ~ -was d ) )affected curvilinearly (linear, P < ,001; quadratic, P < .05) by dietary protein concentration. The effects of dietary energy and protein concentrations on energy intake were consistent with their effect on DMI. Because sex affected ME intake, expressed as Mcal/d but not as kcal/(kg75.d), the effect of
sex on ME intake can be attributed to body size differences between male castrates and females. Breed influenced ME intake expressed either as Mcal/d or as k ~ a l / ( k g . ~ ~A .d). confounding effect of dietary energy density on CP intake was observed. The decrease in CP intake as a result of ar~increase in dietary energy density contributed to the negative effect of dietary energy density on DMI. Protein levels may not have been adequate for maximal growth rate in the high-energy, lowprotein diet. This is evidenced by the effects of interaction of energy and protein concentrations on ME intake (Mcal/d, P < .05; kcal/ kg.75.d, P < .01) and on ME utilization for growth (kcal ME consumed/g gain, P < .001). Goats fed the high-energy, low-protein diet had lower ME intakes (1.90 Mcal/d or 155 k ~ a l / ( k g . ~ ~ .and d ) ) ME utilization for growth (6.1 kcal ME consumed d/g gain) compared with treatment means of goats fed the other eight diets. Average daily gain for the 16-wk period was 88, 97 and 113 g/d for the high-energy diet with low-, medium- and highprotein levels, respectively. This trend was similar for all growth intervals observed. However, the interaction of energy and protein concentrations on ADG was not significant. The effect of sex on protein intake was largely due to body size differences, as observed for ME intake. Breed affected CP intake independently of body size.
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Energy Low Medium
CP intake
No.
1756
LU AND POTCHOLBA TABLE 4. EFFECT OF BREED AND SEX ON LlVE WEIGHT GAlN AND INTAKE Breed
Item
45
45
133 104 100 91 107
127 111 106 101 111
895 1,016
775 897 978 1,053 926
1
.ow
1,102 1,028
Sex
Nubian
Male castrates
54
36
NS NS NS NS NS
130 105
128 111
1W
102 110
*** ** **
823 935 1,016 1,041 954
853 989 1,070 1,132 1,011
**
Pa
NS NS NS NS NS
97
107 92
NS
aP, level of significance; NS, P > .10 ', P < .lo; *, P < .05; **, P < .01; bAge of goat kids, wk
Estimates of ME and CP utilization for growth above maintenance are given in Table 5. Dietary energy density affected energy utilization for growth curvilinearly and for protein utilization linearly ( P < .001). Dietary protein level affected protein but not energy utilization for growth. No effect of sex on energy and protein utilization for growth was detected. However, Nubian kids appeared to be more efficient in energy and protein utilization for growth, as evidenced by lower kcal ME and g CP for each gram of gain (P < .OOl>. Nubian goats in general have a greater mature size than Alpine goats. The effect of dietary energy density on energy utilization for gain could be attributed to differences in gut fill and composition of gain, as discussed previously. Effect of dietary energy density on utilization of protein for gain could be attributed to the energy to protein ratio. The highest concentrate diet may have enhanced microbial incorporation of NH3, which in turn contributed to a higher non-ammonia N flow in the duodenum. The effect of dietary protein level on protein utilization for gain could be explained by an excess of CP and loss of ammonia N in the urine. Such diminishing returns are observed commonly in growing and lactating ruminants. Presumably the Nubian is more efficient in BW gain but less efficient in milk production than is the Alpine goat. Alpine goats produced more milk than the Nubian when dietary, physiological and environmental conditions were similar (Lu et al., 1987). When monthly ME intake was regressed on live weight gain, the slope was 4.60 kcal ME/g
Female
Pa
NS i
NS
** *
***, P < ,001.
of gain (Figure 1). This value was much lower than the recommended value (NRC, 1981). However, the recommended value, 7.25 kcal ME/g of gain, is the mean of three separate observations, 10.18, 5.14 and 6.43 kcal ME/g of g&n, observed from indigenous Malaysian, West African Dwarf and various breeds of Indian goats. The SE for the ME requirement indicated a 95% confidence interval between 3.3 and 5.9 kcal/g of gain, which is slightly to
TABLE 5 . FACTORS AFFECTING UTILIZATION OF ME AND CP FOR GROWTH ABOVE MAlNTENANCE
hem
Energy Low Medium High Protein Low Medium High Sex Male castrates Female
No.
kcal ME g C P consumed/ consumed/ g gaina g gainb
30 30 30
13.0 14.0 8.7
.97
30 30 30
11.4 11.8 12.6
.55
36 54
12.0 11.8
.74 .73
45 45
13.1 10.7 2.5
,615 .15
.77 .47 .74 .92
Breed
Alpine Nubian SE
.%I
aEnergy: linear and quadratic, P < ,001; protein: linear and quadratic, P > .lo; sex, P > .IO; breed, P < .001. bEnergy: linear, P < .001, quadratic, P > .IO;protein: linear, P < ,001, quadratic, P > .IO; sex, P > .lo; breed, P < ,001.
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h'umber Live wt gain, g/d 17 to 20b 21 to 24 25 to 28 29 to 32 17 to 32 DMI. g/d 17 to 20 21 to24 25 to 28 29 to 32 17 to 32
Alpine
1757
INTAKE AND GROWTH OF GOATS
4 4
M
200 -
Y = 2216 (+79)t 4 60 i+ 65iX
500
r = 35
S ~ =X627 p' 0001 n = 360 (48 hidden)
M M
M
'
39003 600
L
I
1
M LML M
m
1
M
M L
i
u
I
-
2 3300L1
3000
-
2 700
-
2 400
-
2 100
-
800
-
1.500
-
w
1
1,200
M
"
#
H
L
M H
M H
n "
H
Y
H
"
H
L H HL M LH H H
i
L
M h H
...
.
n n
n
HM
M
k"
"H
L "
I
1
h
H
M
H
I
l
I
1
I
,
,
I
,
I
,
I
I
I
,
I
I
,
,
substantially lower than all of the values used (Table 6). Requirement values derived from by NRC (1981). When monthly live weight regression and empirical approaches tended to gain was regressed on CP intake, the slope was be lower during 17 to 20 wk of age than at .26 g CP/g of gain (Figure 2). The recom- other intervals. This is attributed to differences mended value (NRC, 1981), .28 g CP or .20 g in composition of gain as discussed previously. DP/g of gain, is the mean of .27, .14 and .17 g The protein-to-fat ratio of gain decreases as DP/g of gain observed for non-dairy breeds. age of ruminants increases. Y intercept values, Different regression equations were derived 2,216 kcal ME and 99 g CP, were equivalent when the requirements were adjusted for BW to values for maintenance plus high activity differences. The equation for the energy recommended by NRC (1981). This implies requirement is y = 197 (f5)+ .35 (k .04)x, r = that goats require substantial amounts of ME .40, where y is ME intake (k~al/(BWk,.~~.d)) and CP for activity during 4 to 8 mo of age. and x is rowth rate (g/d). The intercept, 197 Although kids were housed in individual pens, ) , size of pens was large enough to allow k ~ a l / ( k g Sd), . ~ is larger than 101 k ~ a l / ( k g ~ ~ . dthe which was used to calculate maintenance active exercise. Compared with calves and requirement by M C (1981). This implies that lambs, kids were extremely active in jumping additional energy might have been needed for and moving both in and out of pens. When the activity. The equation for the protein require- growth requirements considering high activity ment is y = 8.78 (f.37) + .02 (f.OO)x, r = .33, ( 3 5 x maintenance) are calculated using the where y is CP intake (g/(BWkg.75-d))and x is empirical approach, the difference between regression and empirical approaches was regrowth rate (g/d). When energy and protein requirements per duced (Table 6). Regardless of sex and breed, three facunit of weight gain were derived from regression analysis, values were much smaller than tors-dietary DE, live BW and ADG-were the those derived from the empirical approach best variables to predict DMI of growing kids,
s
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M
1758 275
250
LU AND POTCHOIBA
,
Y
=
I =
99 (55) + 2612 0 4 ) X
40
Syx=408 p c 0007 n = 360 (36 hidden)
b
M
i
200
-
D 0,
w Y
2
175
z_
," +
B
150
'$
125
t
7
a
0
100
75
5c I
I
I
100
80
I
60
I
40
1
1
1
1
1
20
0
20
40
60
1
80
1
100
1
120
1
140
1
160
1
180
1
200
1
1
1
1
220 240
1
260
280
300
LIVE WEIGHT GAIN g d
Figure 2 The relauonship betueen monthly CP make and live weight gam in Alpme and Nubian goats fed high (H)-, medium (M)and low (L)-protem diets
except for goats 29 to 32 wk of age (Table 7). Dietary ADF substituted for dietary DE to best estimate DMI of goats during 29 to 32 wk of age. In addition to dietary DE, live BW and AM;, the independent variables tested in stepwise regression analysis were dietary CP and ADF concenmations. Although dietary CP affected DMl (Table 2), it was not among the best three variables to predict DMI in growing
goats. Dietary ADF, live BW and ADG were the best three variables to predict DMI of Nubian and of female goats 17 to 32 wk of age. The R2 for intake increased from .58 to .76 as the age of kids increased from 17 to 32 wk. The R2 for intake of all kids from 17 to 32 wk of age was .73 with a Sy.x equal to 13% of the mean. A slight improvement in R' was detected when separate prediction equations
TABLE 6. METABOLIZABLE ENERGY AND CF' REQUIREMENTS FOR GROWTHa kcal ME& gain Age, wk
Regression
Maintenance Maintenance + onlyb activityC
17 to 20 21 10 24 25 to 28 29 to 32 17 to 32
4.6 5.7 7.1 6.9 4.6
9.3 14.3 12.8 15.6 11.9
aN = 90.
bME or CP = aW.75 + b (ADG). 'ME or CP = 1.75 aW.75 + b (ADG).
4.8
I .9 7.2 9.3 5.9
Regression
g CP/g gain Maintenance Maintenance + onlyb activity'
.32 .33 .34 .36 .26
.57 .9 1 .80 .96 .74
30 .54
.47 .57 .39
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225
1759
IhTAKE AND GROWTH OF GOATS
TABLE 7. PREDICTION EQUATIONS FOR DMI OF GROWING GOATS AT VARIOUS GROWING PERIODS ~~
171032
Class
Breed Alpine Nubian Sex Male castrates Female
~~~
Equation Yab = 1042.2 - 2973x1 + 254x2 + 1 . 7 ~ 3 Y = 16.11 -466.9~1+ 28.3X2 + 1 . 2 ~ 3 Y = 1966.7 - 590.7X1 + 2 9 . 1 ~ 2+ 1.4X3 Y =-901.6+5482.5x4+23.4x2+ l.lx3 Y = 1748.7 - 4 9 5 . 7 ~+~ 1 8 . 4 +~ 3~. 0 ~ 3
No. 90
r2
%.x
p
.58
123
90
152
90 90 90
.64 .68 .76 .73
I67 154
,000 1 ,000 1 .000 1 .0001 ,000I
Y = 1804-487.5~1+ 13.6X2+3.8~3 Y = 4 9 1 + 4128x4 + 1 6 . 7 ~ + 2 2.9~3
45 45
.78 .?5
117 118
.ooo1
Y = 1301 - 356.2~1+ 1551x4 + 47x3
36 54
.70
141 117
,0001
Y =-726 + 3891x4 + 2 6 . 7 ~ 2+ 1.7X3
.77
127
.om1 ,0001
a Y , DMl (g/d); X I . dietary DE (Kcal/g); x2. BW (kg); x3, ADG (g/d); x4. dietary ADF (8). bBased on the best three variables model lound.
were developed for Alpine. Nubian and female kids. Implications
The estimated energy requirement for growth determined by regression was 33% lower than current (1981) NRC recommendations. The overestimation presumably resulted from underestimating energy needs for activity. The protein requirement for growth was 7% lower than current NRC (1981) recommendations. Prediction equations considering BW, growth rate, sex, breed and dietary energy density allowed estimation of DMI of growing goats. Differences between goat breeds in efficiencies of ME and CP utilization for gain suggest that mature weight (Nubian > Alpine) should be considered when nutrient requirements are estimated. Literature Cited AOAC. 1984. Official Methods of Analysis (13th Ed.). Association of Official Analytical Chemisb. Washington. DC. Akinsoyinu, A. 0. 1974. Studies on protein and energy utilization by the West African dwarf goats. Ph. D. Dissertation. University of Ibadan. Nigeria. Blaxier. K. L. and J . L. Clapperton. 1965. Prediction of the amount of rnelhane produced by ruminants. Br. J. Nutr. 19:511.
Cochran. W. G. and G. W.Cox. 1957. Experimental Designs (2nd Ed.). John Wiley. New York. Devendra. C. 1967. Studies in the nutrition of h e indigenous goat of Malaysia. 11. The requirements of live weight gain. Malays. Agnc. J . 46:98.
Garrett. W. N. 1980. Energy utilization of growing cattle as determined in 72 comparative slaughter experiments. In: L. E. Mount (Ed.) Energy Metabolism. pp 3-7. Buttenvonhs, London, U K . Goering. H. K.. and P. J. Van Soest. 1970. Forage fiber analyses (apparatus, reagents, procedures, and some applications). Agnc. Handbook 379, ARS, USDA, Washington, DC. Huston, J . E., B. S. Rector. W. C. Ellis and M. L. Allen. 1986. Dynamics of digestion in cattle. sheep, goats and deer. J . Anim. Sci. 62208. Jindal, S. K., A. K. Mehta and M.V.N. Rao. 1980. Influence of dietary energy on the body composition and feed conversion efficiency during growth in goats. Indian J. Nutr. Dirt. 17:95. Lu, C. D., N. A. Jorgensen and G. P. Barrington. 1980. Intake, digestibility and rate of passage of silages and hays from wet fractionation of alfalfa. J. Dairy Sci. 63: 2051. Lu, C. D., T. Sahlu and J. M. Fernandez. 1987. Assessment of energy and protein requirements for growth and lactation in goats. h o c . 1V Int. Conf. on Goats 2:1229. Moe. P. W. and H. F. Tyrrell. 1976. Estimating metabohable and net energy of feeds. Prcc. 1st hi. Symp. on Feed Composition, Animal Nutrient Requirements. and Compuierization, Feedstuffs lnst.. Logan, UT. NRC. 1978. Nutrient Requirements of Dairy Catlle (5th Ed.). National Academy Press, Washington, DC. NRC. 1981. Nutnent Requirements of Goats. National Academy Press, Washinyon, DC. NRC. 1985. Nutrient Requirements of Sheep (6th Ed.). National Academy Press, Washington, DC. NRC. 1987. Predicting feed intake of food-producing animals. National Academy Press, Washington, DC. Rajpoot, R. L. 1979. Energy and protein in goat nutnilon. Ph.D. Dissenation. Raja Balwant Singh College. Bichpuri (Agra), India. Snedecor, G. W. and W. G. Cochran. 1967. Statistical Methods (6th Ed.). Iowa State Univ. Press, Ames. SAS. 1979. SAS User’s Guide: Statistics. SAS Inst.. Inc.. Cary, NC.
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Age, wk 17 to 20 21 10 26 25 to 28 29 10 32 17 to 32 171032
