Lactation Performance of sows Ini ected with Growth Hormone-Releasing flactor During Gestation and(or) Lactation1 2 3 C. Farmer, D. Petitclerc, G. Pelletier, and P. Brazeau4 Agriculture Canada, Research Station, Lennoxville, Quebec J1M 123, Canada
throughout the study. Weights of the pigs at any one time or survival until weaning were not affected by treatments (P > .1). Sows injected with GRF during GEST ( P = .05) and(or1LACT (P c: .01) were lighter than CTL sows at weaning; in addition, sows treated during lactation had less backfat (P < .01).Milk production or composition and serum prolactin (PRL) concentrations were unaltered by treatments (P > .I). Mean growth hormone (GH) concentrations, area under the GH curve (P < .011, and insulinlike growth factor I concentrations (P e .05) were increased in sows treated with GRF during lactation. A reduction in daily feed consumption during the 4th wk of lactation (P e .01) also was observed in LACT = 4.5 vs 5 . 4 kg, SEM = 2) compared with sows those sows receiving saline during lactation. In conclusion, exogenous GRF given during lactation decreased feed intake of sows, yet they were able to maintain their milk production and litter performance, possibly through better utilization of their protein sources.
(x
Key Words: Lactation, Pregnancy, Sows, Growth Hormone-Releasing Factor, Milk Yield J. Anim. Sci. 1992. 70:2636-2642
Introduction Litter performance is a factor of major economic importance in a swine farrowing unit. One way of improving it may be via a n increase in milk
'Lennoxville Research Station contribution no. 381. 2This work was supported by Sanofi Recherche, Montpellier, France. 3We thank L. Thibault, D. Bournival, J. Brochu, G. Bertrand, L. St-James, D. Dion, and A. Belleau for their invaluable technical assistance; M. Morissette, M. Vanier, I. Bergeron, Y. Dubois, D. Morissette, and S. Morissette for care and injections of the animals; and L. Boisvert for secretarial assistance. 4Univ. of Montreal, Laboratory of Neuroendocrinol., NotreDame Hospital, Montreal, Quebec, Canada H2L 4M1. Received December 18, 1991. Accepted April 14, 1992.
production of the sows, which would in turn improve weaning weights of the pigs (Noblet and Etienne, 1989). 153 Administration of porcine growth hormone [GHI during gestation and lactation or during lactation only was shown to increase milk production of sows by 2 16% in the 3rd or 4th wk of lactation (Spence et al., 1984; Harkins et al., 1989). Growth of the nursing pigs paralleled the increase in milk production of the sow (Harkins et al., 1989). Such increases might also be observed when one injects growth hormone-releasing factor (GRF) into sows; however, twice daily injections of 20 pg/kg of GRF from d 5 to 25 of lactation did not alter milk production or pig weight gain (Dubreuil et al., 199Oa). This lack of effect could be explained by a n insufficient dose of
2636
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ABSTRACT2 Fiftytwo Yorkshire x Landrace gilts were equally allotted to four treatments: 1) controls, saline injections ICTL); 2) injections of 12 mg of growth hormone-releasing factor (GRF) (1-29)NHz thrice daily (0700, 1500, and 2300) from d 100 of gestation until parturition (GEST); 31 injections of GRF thrice daily from d 3 to 29 of lactation (LACTI; and 4) injections of GRF thrice daily during gestation (d 100 to parturition) and lactation (d 3 to 29) (GEST-LACT).Within 48 h of birth, litters were standardized to 9 k 1 pigs. Weights of the pigs were recorded weekly from birth ( e 24 h) until weaning (d 30)and on d 42 and 56. Weights of gilts at mating, d 110 of gestation, 1 d postfarrowing, and a t weaning also were recorded. On d 24 of lactation, milk yield was estimated by the weighsuckle-weigh method, and a representative milk sample was obtained the next day. Jugular vein cannulas were inserted into six sows per treatment on d 26, and a 6-h blood profile (sampling every 20 min from 0600 to 12001 was obtained on d 29. Daily feed consumption of sows was recorded
GRF AND LACTATION IN SOWS
2637
Table 1. Composition of diets
GRF, because only small increases in overall GH concentrations were observed (Dubreuil et al., 1990a).
Materials and Methods Animals and Treatments. Fifty-two Yorkshire x Landrace gilts were equally allotted to the following four treatments: 11 saline injections (CTLI; 2) GRF injections from d 100 of gestation until parturition (GESTI; 3) GRF injections from d 3 until d 29 of lactation (LACTI; and 4) GRF injections from d 100 to the end of gestation and from d 3 to 29 of lactation (GEST-LACT). Injections of GRF (1-29)NH2 (3 mL, 12 mg per injection) or saline were given subcutaneously three times a day, at 0700, 1500, and 2300. Mean BW (k SEMI of the gilts at d 110 of gestation (150.3 f 4.9 kg) was similar across treatments. Backfat thickness a t the last rib (using ultrasound) and BW were recorded at d 110 of gestation, on the day after parturition, and a t weaning (30 d of lactation); BW was also determined a t mating. Animals were fed 2.2 kg/d of a corn-soybean meal diet (14.2% CP, Table 1) and .3 kg/d of wheat bran as top-dressing during gestation. The lactation diet was fed to appetite and contained 18.3% CP (Table 1) in a n attempt to provide sufficient protein in the event that GRF would reduce feed intake. Total feed refusals were weighed daily throughout the experiment. Gilts were transferred to raised farrowing crates on d 110 of gestation and farrowing was induced with prostaglandin (Planate, Coopers Agropharm, Willowdale, ON, Canada) on d 112 (2 mL i.m., 184 pg). All pigs were weighed and sexed within 24 h of birth and litters were standardized to 9 f 1 pigs a t 48 h postpartum. Remaining pigs were then
Gestation diet, %
Ingredient Corn Barley Soybean meal (48% CPI Animal fat Vitamin and mineral premixa Calculated nutrient content, as fed ME, k c a l k g CP, % Lysine, % Ca, % P, %
Na, % ~~
Lactation diet, TO
5
57 11 25 2 5
3,075 14.2 .64 1.2 .72 .18
3,248 18.3 .Q1 1.2 .74 .18
43
40 12
-
~
&Providedthe following per kilogram of complete diet: vitamin A, 15,000 IU; vitamin D, 1,500 IU; vitamin E, 40 IU; choline, 400 mg; niacin, 33 mg; pantothenic acid, 16 mg; riboflavin, 6 mg; menadione 2.2 mg; folic acid, 1 mg; pyridoxine, 3.5 mg; thiamine, 3 m g ;vitamin BIZ, 30 pg;biotin, 200 pg;Zn, 150 mg; Fe, 200 mg; I, 1 mg; Cu, 10 mg; Mg, 30 mg; Co, .5 mg; and Se, . I mg.
weighed and were weighed again a t 7, 14, 21, 30, 42, and 56 d of age. On d 24 of lactation, milk production was estimated using the weigh-suckle-weigh method described by Lewis et al. (1978). The next day, a representative milk sample was obtained by collecting milk from three glands on each side of the udder after a n i.v. injection of 1.5 mL of oxytocin (20 IU/mL; P.V.U., Victoriaville, PQ, Canada). Pigs were separated from their dam for 90 min before oxytocin was injection. On d 26 of lactation, jugular vein cannulas were surgically inserted (Ford and Maurer, 1978) in six sows from each treatment. Three days later, serial blood samples were obtained every 20 min from 0600 to 1200. Blood samples were put on ice and centrifuged within 20 min for glucose, free fatty acids (FFA), and insulin-like growth factor I (IGF-I1 analyses and left at room temperature for 4 h, stored overnight at 4 O C, and centrifuged the following day for other hormonal and metabolite assays. Prolactin (PRL)and GH assays were performed on serum, and IGF-I (EDTA tubes), glucose (heparinized tubes), and FFA (heparinized tubes) assays were done on plasma. Sera and plasma samples were frozen at -2OOC until they were assayed. Concentrations of GH and PRL were determined on all samples, whereas concentrations of IGF-I, albumin, globulin, urea, and protein were determined in the first sample only, and those of glucose, insulin, triiodothyronine (T$, thyroxine (T4),and FFA were obtained on the first three samples. Peptides. Purity of porcine GRF(1-291NH2 (provided by Sanofi Recherche, Montpellier, France) was 93.6%, with a peptide content of 85%. Stock solutions of GRF were prepared a t concen-
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Treatment with GRF during gestation may also prove to have beneficial effects on performance of the pigs. Exogenous GRF during gestation increased milk production of ewes during a 6-wk lactation period (Kann et al., 19881, and administration of porcine GH during gestation improved traits related to blood glucose homeostasis of newborn pigs (Spence et al., 1984; Kveragas et al., 19861. The purpose of the present trial was to determine the effects of thrice-daily injections with 12 mg of GRF during the last 14 d of gestation and(or1 from d 3 to 29 of lactation in sows. Specific objectives were to establish the effects of exogenous GRF on 11 the endocrine and metabolic profiles of sows on d 26 of lactation, 21 milk production and milk composition on d 24 and 25, respectively, 3) BW, backfat thickness, and feed intake of sows, and 4) growth rate of pigs up to 56 d of age.
2638
FARMER ET AL.
Statistical Analyses. The GLM procedure of SAS (1982) was used for statistical analyses. Data from pigs were analyzed according to a split-plot design with treatment, sow (treatment), and sex as main factors. Sow within treatment was the error term for treatment and sow (treatment) x sex was the error term for sex and treatment x sex. Treatment effects were determined with orthogonal contrasts according to a factorial arrangement. Main effects were GRF injections during gestation and during lactation, respectively. Milk production and composition as well as feed intake, weight gain, and backfat data for sows were analyzed as one-way analyses of variance with treatment as main effect. Orthogonal contrasts, according to a factorial arrangement, were used to differentiate treatment effects. The main effects (GEST and LACT) and the interactions were tested. Similar analyses were done for IGF-I, total protein, albumin, globulin, urea, and for the mean of the three values obtained for glucose, insulin, T3, T4, and FFA on d 29 of lactation. Statistical analyses for GH and PRL were done on preinjection levels (mean value of first four samples), area under the curve postinjection (AUC; estimated by the trapezoidal summation method; Abramowitz and Stegun, 19721, peak, and average concentrations.
Results Body weights of pigs a t birth, 2, 7, and 14 d of age (Table 2) were similar across treatments (P > ,I),but there was a tendency (P 5 .1) for pigs to be heavier at 21 and 30 d when the dam was injected with GRF during gestation. However, these tendencies were not maintained in the postweaning period; there was no significant main effect on weights at 42 or 56 d (Table 2). The GEST x LACT interaction, on the other hand, was significant at 42 and 56 d of age but was most likely caused by the heavy weight of CTL pigs, which the GESTLACT pigs had equalled during the postweaning period. Treatments did not alter (P > .1) 1-ittersize at birth or survival until weaning of pigs in litters that had been standardized to nine pigs at 48 h. Male pigs, on the other hand, were heavier (P < .05) than female pigs at birth, 2, 7, 30, 42, and 56 d, whereas female pigs weighed more (P c .05) a t 21 d; there were no significant interactions between sex and treatments. Weight of gilts across treatments were similar (P > . I ) at mating, 110 d of gestation, and on the day after parturition, but all treated gilts weighed less (P c .05) than CTL gilts at weaning (Table 3). Gilts receiving GRF during gestation gained more (P < .05)from mating to 110 d of gestation, whereas weight losses from d 110 of gestation until 24 h postpartum were unaltered by
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trations of 5 mg/mL in 520 cis, of .1 N HC1 and the volume was adjusted by adding 480 pL of .1 N NaOH. Subsequent dilutions were prepared in .9% NaCl. Hormone and Metabolite Assays. Porcine GH was assayed by a n established RIA (Dubreuil et al., 1990b). The first antibody (G. DesCotes, Sanofi) showed no cross-reactivity with I pg/mL of thyrotropin, LH, FSH, or 5 ,ug/mL of PRL. The intra- and interassay CV were 5.7 and 8.7%, respectively. Sensitivity of the assay was .2 ng/mL. Concentrations of IGF-I were determined according to a previously described RIA (the first antibody was graciously donated by L. Underwood and J. J. Van Wyk and the NIDDK through the NHPP, University of Maryland School of Medicine; Farmer et al., 1990). Sensitivity of the assay was 6 pg per tube, and the intraassay CV was 4.9%. Porcine insulin concentrations were determined according to a double-antibody assay procedure (Dubreuil et al., 1990b).Sensitivity of the assay was .02 ng per tube, and the intraassay CV was 5.2%. Serum concentrations of PRL were quantified by a homologous double-antibody RIA procedure (Robert et al., 1989). Sensitivity of the assay was .1 ng per tube. The intra- and interassay CV were 14.2 and 11.3%, respectively. Serum T3 (Immunochem, Carson, CAI and T4(Biomega Diagnostic, Montreal, PQ, Canada) concentrations were obtained by RIA using commercial kits. Intra- and interassay CV were 8.0 and 10.3% for T4, and the intraassay CV was 9.1% for Ts. Glucose was determined by a n enzymatic colorimetric method using a commercial kit (Boehringer Mannheim, Laval, PQ, Canada). The intra- and interassay CV were 1.8 and 1.3%, respectively. An enzymatic analysis (NEFA-C kit; WAKO Chemicals USA, Dallas, TX) was also used for FFA quantification. Intra- and interassay CV were 2.4 and 2.6%, respectively. Total protein, albumin, globulin, and urea content in serum were measured with a n automatic Hitachi 705 blood analyzer (Boehringer Mannheim, Meylan, France), using the Wellcome Clinical Chemistry Quality Control Program (Wellcome Foundation, Temple Hill, Dartford, UK) for daily calibration. Chemical Analyses. Milk protein was determined by a micro-Kjeldahl procedure (Kjeltec Auto System, Tecator AB, Hoganas, Sweden) and milk fat and total milk solids were measured according to standard procedures (AOAC, 1980). Milk lactose was determined enzymatically (Boehringer Mannheim, Indianapolis, IN) as follows: lactose was hydrolyzed to glucose + P-galactose which, when added to nicotinamide adenine dinucleotide (NAD),resulted in NADH formation. The amount of NADH formed was measured by absorbance under ultraviolet wavelength (365 nM). Coefficients of variation were c 5%.
2639
GRF AND LACTATION IN SOWS
Table 2 . Least squares means for body weight (kg) of pigs born of sows injected thrice daily with 12 mg of growth hormone-releasing factor or saline during the last 10 days of gestation (GEST] and(or) lactation (LACT) P-valuea GEST Weightsb
Control
GEST
GESTLACT
LACT
X
GEST ~
h
1.52 2.53 4.11 5.76 8.08 11.84 19.80
d
d d d d d
1.57 2.63 4.42 6.31 8.45 10.99 18.77
1.59 2.69 4.43 6.11 8.17 11.09 18.75
~~
NS
1.52 2.74 4.42 6.23 8.58 11.98 19.92
NS NS .07 .10
NS NS
LACT
SEM
~~
NS NS NS NS NS
NS
NS
NS NS NS NS .o 1
NS
.03
.84 .10 .14 .18 .23 .27 .49
&Probability value of orthogonal contrasts. NS = nonsignificant (P > .11. bMean litter size over all ages was 9.9, 10.8, 10.5 and 10.6 for Control, GEST, LACT and GESTLACT sows, respectively; SEM = .68.
also higher (P < .05) with GRF treatment during lactation, but this is most likely due to the low value for GEST sows (Table 4). There was a tendency (P 5 .1) for FFA concentrations to be increased in gilts from all treatments (Table 4). Milk production of sows on d 24 of lactation was similar across treatments (P > .I) and milk composition was unaltered (P > . l ) , except for a tendency (P = .09)toward greater milk fat in sows receiving GRF during lactation (Table 5). The average of least squares means across treatments were 8.82 kg/d for milk production (SEM = .35), 6.6% milk fat (SEM = .34), 18.3% milk solids (SEM = .37), 5.6% milk protein (SEM = .13), and 4.7% milk lactose (SEM = .12). Daily feed consumption of sows during the first 3 wk of lactation was not affected by treatments (P > .1) but was decreased (P < .0011 during the 4th wk of lactation in animals injected with GRF during lactation (Figure 1).
treatments (P > .01). Weight losses of gilts from parturition until weaning were increased by both treatments, and gilts treated in lactation gained less weight (P < .05) from mating to weaning (Table 3). Backfat was similar at mating and at 24 h postpartum in sows across treatments (P > .1) but was significantly reduced at weaning in sows receiving GRF during lactation (Table 3). However, no detrimental effects of treatments on animal health were noted. Reinjection GH concentrations were similar (P > .l) for gilts across treatments (Table 41. Mean GH concentrations, GH peak, and GH AUC were increased (P = .001) on d 26 of lactation in gilts receiving GRF during lactation (Table 4). None of the PRL variables was affected by treatments (P > .l, Table 41, but concentrations of IGF-I were decreased (P < .05) in GEST and increased (P < .05) in LACT sows (Table 4). Glucose values were
Table 3. Least squares means for body weight, body weight change, and backfat of gilts injected thrice daily with 12 mg of growth hormone-releasing factor (1-29)NHz or saline during the last 10 days of gestation (GEST) and(or) lactation (LACT)
Item
Control ~
GEST
LACT
GESTLACT
P-vduea GEST
LACT
NS NS
NS
SEM
~
Weight, kg Mating 110 d Gestation 24 h Postpartum Weaning Weight change, kg 24 h Postpartum to weaning Mating to weaning Backfat a t weaning, mm
154 217 193 170
151 222 197 166
154 218 192 160
143 209 185 147
-23 16
-3 1 15
-32 6.5
-38 4.7
15.9
16.3
20.8
19.5
NS
NS
.05
,002
5 5 4.5 4.4
.05
NS
.04 .01
3.6 3.9
NS
.005
1.e
NS
&Probability value of orthogonal contrasts. NS = nonsignificant (P > .11. There were no significant interactions.
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48 7 14 21 30 42 56
LACT
FARMER ET AL.
2640
Blood urea was drastically reduced (P .c .001) on d 26 of lactation in LACT sows, whereas globulin (P < .01) and total protein increased (P = .05; Table 5). Albumin decreased (P = .O21 in GEST-LACT gilts (Table 5).
~
A
A
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3rd and 4th wk of lactation. A similar decrease in feed intake was noticed in the 4th wk of lactation in the present trial, but feed intakes of sows from all treatments were lower than in the study of Harkins et al. (1989). This may have counteracted any possible effects of exogenous GRF on milk production, because the greatest increase due to treatment would be expected during that period of Discussion time. The decrease in the a1bumin:globulin ratio observed in LACT sows in the present study In the present study a dose of 12 mg of denotes a protein abnormality that may have been exogenous GRF injected three times daily at the caused by the reduced protein intake. This is end of gestation and(or1 during lactation did not substantiated by the lower blood urea content and increase milk production or alter milk composition higher total protein content. Such results suggest of sows. Whether this lack of effect was due to the a more efficient utilization of protein sources in transient delivery of GRF or to the significant LACT sows, which was sufficient to maintain milk reduction in feed intake during the 4th wk of production, but not to increase it. lactation is not known. The latter explanation Harkins et al. (1989) suggested that the seems most likely. Harkins et al. (19891 observed decreased feed intake in GH-treated sows may be an increase in milk production of sows injected due to alterations in the feedback system that with GH, but feed intake was reduced during the regulates feed intake or to impurity of the hormone preparation. The latter reason may not be the case in the present trial because GRF was produced by chemical synthesis and was purified. The basis for the effect of elevated GH concentrations on feed intake is not clear yet. The decreased 6 feed consumption seen in the present trial could be related to alterations in the system regulating feed intake, such as elevated glucose or FFA concentrations. In sheep, exogenous GRF given to ewes from d 105 to 115 of gestation increased milk yield during the succeeding lactation (Kann et al., 19881, whereas in cattle, prepartum injections of a GRF agonist had no effect on milk production and on calf ADG during the first 2 mo of lactation (Simpson et al., 1989). With regard to sows, immunization against GRF before breeding, which prevented pulsatile release of GH during gestation and lactation, decreased milk production on d 19 of lactation, without affecting growth of pigs (Esbenshade et al., 1989). It is not known whether CTL the immunization exerted its effects on milk 1 GEST via the increased antibody titers production I LACT against GRF during gestation and(or1during lactaI G EST- LACT tion. Moreover, experiments with exogenous GH showed that the increases in milk production observed in sows injected with GH were not higher 2 3 4 WEEK OF LACTATION when the animals were treated during gestation and lactation than when they were treated only during lactation (Spence et al., 1984; Harkins et al., Figure 1. Feed consumption (least squares means) 1989). Cromwell et al. (198913) also found that throughout lactation for gilts injected thrice daily with exogenous GH given during late gestation did not 12 mg of growth hormone-releasing factor(1-29)NHz or increase milk production of lactating sows, and saline (CTL = control) during the last 10 d of gestation Kveragas et al. (1986) observed that exogenous GH (GEST) and(or)lactation (LACT).Values of SEM are .12, given during the last 21 d before farrowing did not .24, .23,and .24 for wk 1 to 4 of lactation, respectively. significantly increase milk volume on d 14 of The probability level is > .1 for wk 1 to 3 and < ,001 lactation. These results corroborate our finding for wk 4.
2641
GRF AND LACTATION IN SOWS
Table 4. Least squares means for growth hormone (GH) variables, insulin-like growth factor I (IGF-I), prolactin (PRL), free fatty acids (FFA), and glucose concentrations in gilts injected thrice daily with 12 mg of growth hormone-releasing factor(1-29)NHZ or saline during the last 10 days of gestation (GEST) and(or) lactation (LACT)"
GEST Item
GEST
LACT
5.7 5.6 8.2 1,779 88.3 44.1 250 5.O
4.8 6.1 9.0 1,912 64.8 36.1 517 4.3
6.0 13.0 33.4 4,149 118.5 38.0 53 1 5.1
5.0 11.8 33.3 3,768 80.7 27.9 512 5.2
X
GEST
LACT
LACT
SEM
NS
.6 1 .o 4.1 332 1.1 5.9 73 .2
.01
.001 .001 .001 .03
NS
NS
NS NS NS NS NS NS
.10
.07 .03
.06 .07
NS NS NS NS
NS
&Blood samples were obtained every 20 min for 8 h on d 26 of lactation. "Probability value of orthogonal contrasts; NS = nonsignificant (P > .I).
that GRF injections during late gestation do not increase milk production of lactating sows. The discrepancy between our results and those obtained with GRF immunization (Esbenshade et al., 1989) may result from the large individual variations in milk production and the small sample size of the latter study (five treated sows vs four controls). Even though positive effects of GH on milk production of sows were reported (Spence et al., 1984; Harkins et al., 1989; Smith et al., 19911, it is still debatable whether GH does have a galactopoietic effect in swine, because other experiments have shown no increase in milk production
of sows injected daily (Cromwell et al., 1989a) or once every 3 d (Crenshaw et al., 1989; Cromwell et al., 1989b) with GH. Biological activity of GRF in the present trial is indicated by the increased GH and IGF-I concentrations seen in sows treated during lactation and by the decreased backfat thickness observed at weaning in these same animals. The increased FFA concentration in treated sows also denotes their negative energy balance and the utilization of body reserves. Unlike GH, which caused the deaths of a number of sows (Kveragas et al., 1986; Cromwell et al., 1989b; Smith et al., 19911, GRF showed no harmful effect on health of lactating
Table 5. Least squares means for milk yield and composition, and urea, total protein, albumin, and globulin content in gilts injected thrice daily with 12 mg of growth hormone-releasing factor(1-29)NHz or saline during the last 10 days of gestation (GEST) and(or] lactation (LACT)" P-value" GEST Item Milk yieldc, kg/d Milk DMd, % Milk fatd, % Milk lactosed, O/O Milk proteind, O h Urea, mmol/L Total protein, g/L Albumin, g/L Globulin, g/L Albumin:globulin ratio
Control
GEST
LACT
GESTLACT
8.5 17.9 8.2 4.9 5.6 8.1 71.5 44.8 28.7 1.139
9.0 18.2 6.3 4.6 5.6 8.7 72.6 47.2 25.4 1.87
9.0 18.7 7.0 4.6 5.7 4.9 75.5 46.4 29.0 1.60
8.7 18.4 6.8 4.6 5.7 4.2 74.1 44.4 29.7 1.52
X
GEST NS NS NS NS NS NS NS NS NS NS
LACT
NS NS .09
NS NS
LACT
SEM
NS NS NS NS
.35 .36 34 .12 .13 .5 1.3 .8 1.1 .07
.0001 .05
NS NS NS
NS
.02
.008 .008
NS NS
&Blood samples collected on d 28 of lactation. "Probability value of orthogonal contrasts; NS = nonsignificant (P > .1). d 24 of lactation. d 25 of lactation.
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GH preinjection, ng/mL Mean GH, ng/mL GH peak, ng/mL GH area under the curve, ng.rnin-'.mL-l IGF-I, ng/mL Mean PRL, ng/mL FFA, mEq/L Glucose, mmol/L
Control
GESTLACT
FARMER ET AL.
2642
Implications Treatment of sows with exogenous growth hormone-releasing factor did not increase their milk yield or improve litter performance, most likely because of the decreased feed intake of treated sows during lactation. To assess the full potential of growth hormone-releasing factor for lactating sows, the nutrient requirements of sows with increased milk production must be assessed and a better understanding of the factors that regulate feed intake in sows with elevated growth hormone concentrations must be achieved.
Literature Cited Abramowitz, M., and I. A. Stegun. 1972. Handbook of Mathematical Functions. M. Abramowitz (Ed.). Dover, New York. AOAC. 1980. Official Methods of Analysis (13th Ed.).Association of Official Analytical Chemists, Washington, DC. Crenshaw, T. D., C. M. Grieshop, J. P. McMurtry, and B. R. Schricker. 1989. Exogenous porcine prolactin and somatotropin injections did not alter sow lactation performance. J. Anim. Sci. 67(Suppl. 1):258 (Abstr.1. Cromwell, G. L., T. S. Stahly, L. A. Edgerton, H. J. Monegue, T. W. Burnell, B. C. Schenck, and M. K. Dunlap. 1989a. Weekly administration of recombinant porcine somatotropin to lactating sows. J. Anim. Sci. 67(Suppl. 1):258 LAbstr.1. Cromwell, G. L., T. S. Stahly, L. A. Edgerton, H. J. Monegue, T. W. Burnell, B. C. Schenck, and T. T. Elkins. 1989b. Recombinant porcine somatotropin for lactating sows. J. Anim. Sci. 67(Suppl. 1):257 (Abstr.). Dubreuil, P., G. Pelletier, D. Petitclerc, H. Lapierre, Y.Couture, P. Gaudreau, J. Morisset, and P. Brazeau. 1990a. Influence
of growth hormone-releasing factor and(or) thyrotropin-releasing factor on sow blood components, milk composition and piglet performance. Can. J. Anim. Sci. 70:821. Dubreuil, P., D. Petitclerc, G. Pelletier, P. Gaudreau, C. Farmer, T. F. Mowles, and P. Brazeau. 199Ob. Effect of dose and frequency of administration of a potent analog of human growth hormone-releasing factor on hormone secretion and growth in pigs. J. h i m . Sci. 68:1254. Esbenshade, K. L., J. D. Armstrong, M. T. Coffey, and C. A. Bowie. 1989. Reproductive performance of sows actively immunized against growth hormone-releasing factor (GRF). J. h i m . Sci. 67(Suppl. 1):197 L4bstr.l. Farmer, C., P. Dubreuil, G. Pelletier, D. Petitclerc, and P. Brazeau. 1990. Active immunization against somatostatin in gestating gilts and the effect of transferred immunity on piglets. Can. J. Anim. Sci. 70:211. Ford, J. J.,and R. R. Maurer. 1978. Simple technique for chronic venous catheterization of swine. Lab. Anim. Sci. 28:615. Harkins, M., R. D. Boyd, and D. E. Bauman. 1989. Effect of recombinant porcine somatotropin on lactational performance and metabolite patterns in sows and growth of nursing pigs. J. Anim. Sci. 67:1997. Kann, G., A. PBrier, and J. Martinet. 1988. Use of human growth hormone-releasing factor hGRF 1-29)NHz as a mammotropic hormone in the ewe. J. Anim. Sci. 66(Suppl. 1):389 (Abstr.). Kveragas, C. L., R. W. Seerley, R. J. Martin, and W. L. Vandergrift. 1986. Influence of exogenous growth hormone and gestational diet on sow blood and milk characteristics and on baby pig blood, body composition and performance. J. Anim. sci. 63:1877. Lewis, A. J., V. C. Speer, and D. G. Haught. 1978. Relationship between yield and composition of sow’s milk and weight gains of nursing pigs. J. Anim. Sci. 473334. Noblet, J., and M. Etienne. 1989. Estimation of sow milk nutrient output. J. Anim. Sci. 67:3352. Robert, S., A.M.B. de PassillB, N. St-Pierre, P. Dubreuil, G. Pelletier, D. Petitclerc, and P. Brazeau. 1989. Effect of the stress of injection on the serum concentrations of cortisol, prolactin, and growth hormone in gilts and lactating sows. Can. J. Anim. sci. 69:663. SAS. 1982. SAS User’s Guide: Statistics. SAS Inst. Inc., Cary, NC. Simpson, R. B., J. D. Armstrong, and R. W. Harvey. 1989. Effect of prepartum administration of a growth hormone releasing factor agonist on growth hormone, milk production and interval to ovarian activity in primiparous beef heifers. J. h i m . Sci. 67(Suppl. 11:331 (Abstr.). Smith, V. G., A. D. Leman, W. J. Seaman, and F. VanRavensw a y . 1991. Pig weaning weight and changes in hematology and blood chemistry of sows injected with recombinant porcine somatotropin during lactation. J. Anim. Sci. 69: 350 1.
Spence, C. A,, R. D. Boyd, D. E. Bauman, W. R. Butler, and C. D. Wray. 1984. Effect of exogenous growth hormone on fetal energy storage and lactation performance in sows. J. Anim. Sci. 59(Suppl. 1):246 (Abstr.).
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sows. The reason for this difference is not clear but may be related to hormonal preparation. We can conclude, therefore, that exogenous GRF given during gestation has no beneficial effect on performance of lactating sows and their litters. However, sows receiving GRF during lactation may utilize protein more efficiently, enabling them to maintain their milk production and litter performance in spite of a decreased feed intake. Therefore, the nutritional requirements of animals receiving such treatments would have to be reevaluated to determine the real potential of GRF for lactating sows.
throughout the study. Weights of the pigs at any one time or survival until weaning were not affected by treatments (P > .1). Sows injected with GRF during GEST ( P = .05) and(or1LACT (P c: .01) were lighter than CTL sows at weaning; in addition, sows treated during lactation had less backfat (P < .01).Milk production or composition and serum prolactin (PRL) concentrations were unaltered by treatments (P > .I). Mean growth hormone (GH) concentrations, area under the GH curve (P < .011, and insulinlike growth factor I concentrations (P e .05) were increased in sows treated with GRF during lactation. A reduction in daily feed consumption during the 4th wk of lactation (P e .01) also was observed in LACT = 4.5 vs 5 . 4 kg, SEM = 2) compared with sows those sows receiving saline during lactation. In conclusion, exogenous GRF given during lactation decreased feed intake of sows, yet they were able to maintain their milk production and litter performance, possibly through better utilization of their protein sources.
(x
Key Words: Lactation, Pregnancy, Sows, Growth Hormone-Releasing Factor, Milk Yield J. Anim. Sci. 1992. 70:2636-2642
Introduction Litter performance is a factor of major economic importance in a swine farrowing unit. One way of improving it may be via a n increase in milk
'Lennoxville Research Station contribution no. 381. 2This work was supported by Sanofi Recherche, Montpellier, France. 3We thank L. Thibault, D. Bournival, J. Brochu, G. Bertrand, L. St-James, D. Dion, and A. Belleau for their invaluable technical assistance; M. Morissette, M. Vanier, I. Bergeron, Y. Dubois, D. Morissette, and S. Morissette for care and injections of the animals; and L. Boisvert for secretarial assistance. 4Univ. of Montreal, Laboratory of Neuroendocrinol., NotreDame Hospital, Montreal, Quebec, Canada H2L 4M1. Received December 18, 1991. Accepted April 14, 1992.
production of the sows, which would in turn improve weaning weights of the pigs (Noblet and Etienne, 1989). 153 Administration of porcine growth hormone [GHI during gestation and lactation or during lactation only was shown to increase milk production of sows by 2 16% in the 3rd or 4th wk of lactation (Spence et al., 1984; Harkins et al., 1989). Growth of the nursing pigs paralleled the increase in milk production of the sow (Harkins et al., 1989). Such increases might also be observed when one injects growth hormone-releasing factor (GRF) into sows; however, twice daily injections of 20 pg/kg of GRF from d 5 to 25 of lactation did not alter milk production or pig weight gain (Dubreuil et al., 199Oa). This lack of effect could be explained by a n insufficient dose of
2636
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ABSTRACT2 Fiftytwo Yorkshire x Landrace gilts were equally allotted to four treatments: 1) controls, saline injections ICTL); 2) injections of 12 mg of growth hormone-releasing factor (GRF) (1-29)NHz thrice daily (0700, 1500, and 2300) from d 100 of gestation until parturition (GEST); 31 injections of GRF thrice daily from d 3 to 29 of lactation (LACTI; and 4) injections of GRF thrice daily during gestation (d 100 to parturition) and lactation (d 3 to 29) (GEST-LACT).Within 48 h of birth, litters were standardized to 9 k 1 pigs. Weights of the pigs were recorded weekly from birth ( e 24 h) until weaning (d 30)and on d 42 and 56. Weights of gilts at mating, d 110 of gestation, 1 d postfarrowing, and a t weaning also were recorded. On d 24 of lactation, milk yield was estimated by the weighsuckle-weigh method, and a representative milk sample was obtained the next day. Jugular vein cannulas were inserted into six sows per treatment on d 26, and a 6-h blood profile (sampling every 20 min from 0600 to 12001 was obtained on d 29. Daily feed consumption of sows was recorded
GRF AND LACTATION IN SOWS
2637
Table 1. Composition of diets
GRF, because only small increases in overall GH concentrations were observed (Dubreuil et al., 1990a).
Materials and Methods Animals and Treatments. Fifty-two Yorkshire x Landrace gilts were equally allotted to the following four treatments: 11 saline injections (CTLI; 2) GRF injections from d 100 of gestation until parturition (GESTI; 3) GRF injections from d 3 until d 29 of lactation (LACTI; and 4) GRF injections from d 100 to the end of gestation and from d 3 to 29 of lactation (GEST-LACT). Injections of GRF (1-29)NH2 (3 mL, 12 mg per injection) or saline were given subcutaneously three times a day, at 0700, 1500, and 2300. Mean BW (k SEMI of the gilts at d 110 of gestation (150.3 f 4.9 kg) was similar across treatments. Backfat thickness a t the last rib (using ultrasound) and BW were recorded at d 110 of gestation, on the day after parturition, and a t weaning (30 d of lactation); BW was also determined a t mating. Animals were fed 2.2 kg/d of a corn-soybean meal diet (14.2% CP, Table 1) and .3 kg/d of wheat bran as top-dressing during gestation. The lactation diet was fed to appetite and contained 18.3% CP (Table 1) in a n attempt to provide sufficient protein in the event that GRF would reduce feed intake. Total feed refusals were weighed daily throughout the experiment. Gilts were transferred to raised farrowing crates on d 110 of gestation and farrowing was induced with prostaglandin (Planate, Coopers Agropharm, Willowdale, ON, Canada) on d 112 (2 mL i.m., 184 pg). All pigs were weighed and sexed within 24 h of birth and litters were standardized to 9 f 1 pigs a t 48 h postpartum. Remaining pigs were then
Gestation diet, %
Ingredient Corn Barley Soybean meal (48% CPI Animal fat Vitamin and mineral premixa Calculated nutrient content, as fed ME, k c a l k g CP, % Lysine, % Ca, % P, %
Na, % ~~
Lactation diet, TO
5
57 11 25 2 5
3,075 14.2 .64 1.2 .72 .18
3,248 18.3 .Q1 1.2 .74 .18
43
40 12
-
~
&Providedthe following per kilogram of complete diet: vitamin A, 15,000 IU; vitamin D, 1,500 IU; vitamin E, 40 IU; choline, 400 mg; niacin, 33 mg; pantothenic acid, 16 mg; riboflavin, 6 mg; menadione 2.2 mg; folic acid, 1 mg; pyridoxine, 3.5 mg; thiamine, 3 m g ;vitamin BIZ, 30 pg;biotin, 200 pg;Zn, 150 mg; Fe, 200 mg; I, 1 mg; Cu, 10 mg; Mg, 30 mg; Co, .5 mg; and Se, . I mg.
weighed and were weighed again a t 7, 14, 21, 30, 42, and 56 d of age. On d 24 of lactation, milk production was estimated using the weigh-suckle-weigh method described by Lewis et al. (1978). The next day, a representative milk sample was obtained by collecting milk from three glands on each side of the udder after a n i.v. injection of 1.5 mL of oxytocin (20 IU/mL; P.V.U., Victoriaville, PQ, Canada). Pigs were separated from their dam for 90 min before oxytocin was injection. On d 26 of lactation, jugular vein cannulas were surgically inserted (Ford and Maurer, 1978) in six sows from each treatment. Three days later, serial blood samples were obtained every 20 min from 0600 to 1200. Blood samples were put on ice and centrifuged within 20 min for glucose, free fatty acids (FFA), and insulin-like growth factor I (IGF-I1 analyses and left at room temperature for 4 h, stored overnight at 4 O C, and centrifuged the following day for other hormonal and metabolite assays. Prolactin (PRL)and GH assays were performed on serum, and IGF-I (EDTA tubes), glucose (heparinized tubes), and FFA (heparinized tubes) assays were done on plasma. Sera and plasma samples were frozen at -2OOC until they were assayed. Concentrations of GH and PRL were determined on all samples, whereas concentrations of IGF-I, albumin, globulin, urea, and protein were determined in the first sample only, and those of glucose, insulin, triiodothyronine (T$, thyroxine (T4),and FFA were obtained on the first three samples. Peptides. Purity of porcine GRF(1-291NH2 (provided by Sanofi Recherche, Montpellier, France) was 93.6%, with a peptide content of 85%. Stock solutions of GRF were prepared a t concen-
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Treatment with GRF during gestation may also prove to have beneficial effects on performance of the pigs. Exogenous GRF during gestation increased milk production of ewes during a 6-wk lactation period (Kann et al., 19881, and administration of porcine GH during gestation improved traits related to blood glucose homeostasis of newborn pigs (Spence et al., 1984; Kveragas et al., 19861. The purpose of the present trial was to determine the effects of thrice-daily injections with 12 mg of GRF during the last 14 d of gestation and(or1 from d 3 to 29 of lactation in sows. Specific objectives were to establish the effects of exogenous GRF on 11 the endocrine and metabolic profiles of sows on d 26 of lactation, 21 milk production and milk composition on d 24 and 25, respectively, 3) BW, backfat thickness, and feed intake of sows, and 4) growth rate of pigs up to 56 d of age.
2638
FARMER ET AL.
Statistical Analyses. The GLM procedure of SAS (1982) was used for statistical analyses. Data from pigs were analyzed according to a split-plot design with treatment, sow (treatment), and sex as main factors. Sow within treatment was the error term for treatment and sow (treatment) x sex was the error term for sex and treatment x sex. Treatment effects were determined with orthogonal contrasts according to a factorial arrangement. Main effects were GRF injections during gestation and during lactation, respectively. Milk production and composition as well as feed intake, weight gain, and backfat data for sows were analyzed as one-way analyses of variance with treatment as main effect. Orthogonal contrasts, according to a factorial arrangement, were used to differentiate treatment effects. The main effects (GEST and LACT) and the interactions were tested. Similar analyses were done for IGF-I, total protein, albumin, globulin, urea, and for the mean of the three values obtained for glucose, insulin, T3, T4, and FFA on d 29 of lactation. Statistical analyses for GH and PRL were done on preinjection levels (mean value of first four samples), area under the curve postinjection (AUC; estimated by the trapezoidal summation method; Abramowitz and Stegun, 19721, peak, and average concentrations.
Results Body weights of pigs a t birth, 2, 7, and 14 d of age (Table 2) were similar across treatments (P > ,I),but there was a tendency (P 5 .1) for pigs to be heavier at 21 and 30 d when the dam was injected with GRF during gestation. However, these tendencies were not maintained in the postweaning period; there was no significant main effect on weights at 42 or 56 d (Table 2). The GEST x LACT interaction, on the other hand, was significant at 42 and 56 d of age but was most likely caused by the heavy weight of CTL pigs, which the GESTLACT pigs had equalled during the postweaning period. Treatments did not alter (P > .1) 1-ittersize at birth or survival until weaning of pigs in litters that had been standardized to nine pigs at 48 h. Male pigs, on the other hand, were heavier (P < .05) than female pigs at birth, 2, 7, 30, 42, and 56 d, whereas female pigs weighed more (P c .05) a t 21 d; there were no significant interactions between sex and treatments. Weight of gilts across treatments were similar (P > . I ) at mating, 110 d of gestation, and on the day after parturition, but all treated gilts weighed less (P c .05) than CTL gilts at weaning (Table 3). Gilts receiving GRF during gestation gained more (P < .05)from mating to 110 d of gestation, whereas weight losses from d 110 of gestation until 24 h postpartum were unaltered by
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trations of 5 mg/mL in 520 cis, of .1 N HC1 and the volume was adjusted by adding 480 pL of .1 N NaOH. Subsequent dilutions were prepared in .9% NaCl. Hormone and Metabolite Assays. Porcine GH was assayed by a n established RIA (Dubreuil et al., 1990b). The first antibody (G. DesCotes, Sanofi) showed no cross-reactivity with I pg/mL of thyrotropin, LH, FSH, or 5 ,ug/mL of PRL. The intra- and interassay CV were 5.7 and 8.7%, respectively. Sensitivity of the assay was .2 ng/mL. Concentrations of IGF-I were determined according to a previously described RIA (the first antibody was graciously donated by L. Underwood and J. J. Van Wyk and the NIDDK through the NHPP, University of Maryland School of Medicine; Farmer et al., 1990). Sensitivity of the assay was 6 pg per tube, and the intraassay CV was 4.9%. Porcine insulin concentrations were determined according to a double-antibody assay procedure (Dubreuil et al., 1990b).Sensitivity of the assay was .02 ng per tube, and the intraassay CV was 5.2%. Serum concentrations of PRL were quantified by a homologous double-antibody RIA procedure (Robert et al., 1989). Sensitivity of the assay was .1 ng per tube. The intra- and interassay CV were 14.2 and 11.3%, respectively. Serum T3 (Immunochem, Carson, CAI and T4(Biomega Diagnostic, Montreal, PQ, Canada) concentrations were obtained by RIA using commercial kits. Intra- and interassay CV were 8.0 and 10.3% for T4, and the intraassay CV was 9.1% for Ts. Glucose was determined by a n enzymatic colorimetric method using a commercial kit (Boehringer Mannheim, Laval, PQ, Canada). The intra- and interassay CV were 1.8 and 1.3%, respectively. An enzymatic analysis (NEFA-C kit; WAKO Chemicals USA, Dallas, TX) was also used for FFA quantification. Intra- and interassay CV were 2.4 and 2.6%, respectively. Total protein, albumin, globulin, and urea content in serum were measured with a n automatic Hitachi 705 blood analyzer (Boehringer Mannheim, Meylan, France), using the Wellcome Clinical Chemistry Quality Control Program (Wellcome Foundation, Temple Hill, Dartford, UK) for daily calibration. Chemical Analyses. Milk protein was determined by a micro-Kjeldahl procedure (Kjeltec Auto System, Tecator AB, Hoganas, Sweden) and milk fat and total milk solids were measured according to standard procedures (AOAC, 1980). Milk lactose was determined enzymatically (Boehringer Mannheim, Indianapolis, IN) as follows: lactose was hydrolyzed to glucose + P-galactose which, when added to nicotinamide adenine dinucleotide (NAD),resulted in NADH formation. The amount of NADH formed was measured by absorbance under ultraviolet wavelength (365 nM). Coefficients of variation were c 5%.
2639
GRF AND LACTATION IN SOWS
Table 2 . Least squares means for body weight (kg) of pigs born of sows injected thrice daily with 12 mg of growth hormone-releasing factor or saline during the last 10 days of gestation (GEST] and(or) lactation (LACT) P-valuea GEST Weightsb
Control
GEST
GESTLACT
LACT
X
GEST ~
h
1.52 2.53 4.11 5.76 8.08 11.84 19.80
d
d d d d d
1.57 2.63 4.42 6.31 8.45 10.99 18.77
1.59 2.69 4.43 6.11 8.17 11.09 18.75
~~
NS
1.52 2.74 4.42 6.23 8.58 11.98 19.92
NS NS .07 .10
NS NS
LACT
SEM
~~
NS NS NS NS NS
NS
NS
NS NS NS NS .o 1
NS
.03
.84 .10 .14 .18 .23 .27 .49
&Probability value of orthogonal contrasts. NS = nonsignificant (P > .11. bMean litter size over all ages was 9.9, 10.8, 10.5 and 10.6 for Control, GEST, LACT and GESTLACT sows, respectively; SEM = .68.
also higher (P < .05) with GRF treatment during lactation, but this is most likely due to the low value for GEST sows (Table 4). There was a tendency (P 5 .1) for FFA concentrations to be increased in gilts from all treatments (Table 4). Milk production of sows on d 24 of lactation was similar across treatments (P > .I) and milk composition was unaltered (P > . l ) , except for a tendency (P = .09)toward greater milk fat in sows receiving GRF during lactation (Table 5). The average of least squares means across treatments were 8.82 kg/d for milk production (SEM = .35), 6.6% milk fat (SEM = .34), 18.3% milk solids (SEM = .37), 5.6% milk protein (SEM = .13), and 4.7% milk lactose (SEM = .12). Daily feed consumption of sows during the first 3 wk of lactation was not affected by treatments (P > .1) but was decreased (P < .0011 during the 4th wk of lactation in animals injected with GRF during lactation (Figure 1).
treatments (P > .01). Weight losses of gilts from parturition until weaning were increased by both treatments, and gilts treated in lactation gained less weight (P < .05) from mating to weaning (Table 3). Backfat was similar at mating and at 24 h postpartum in sows across treatments (P > .1) but was significantly reduced at weaning in sows receiving GRF during lactation (Table 3). However, no detrimental effects of treatments on animal health were noted. Reinjection GH concentrations were similar (P > .l) for gilts across treatments (Table 41. Mean GH concentrations, GH peak, and GH AUC were increased (P = .001) on d 26 of lactation in gilts receiving GRF during lactation (Table 4). None of the PRL variables was affected by treatments (P > .l, Table 41, but concentrations of IGF-I were decreased (P < .05) in GEST and increased (P < .05) in LACT sows (Table 4). Glucose values were
Table 3. Least squares means for body weight, body weight change, and backfat of gilts injected thrice daily with 12 mg of growth hormone-releasing factor (1-29)NHz or saline during the last 10 days of gestation (GEST) and(or) lactation (LACT)
Item
Control ~
GEST
LACT
GESTLACT
P-vduea GEST
LACT
NS NS
NS
SEM
~
Weight, kg Mating 110 d Gestation 24 h Postpartum Weaning Weight change, kg 24 h Postpartum to weaning Mating to weaning Backfat a t weaning, mm
154 217 193 170
151 222 197 166
154 218 192 160
143 209 185 147
-23 16
-3 1 15
-32 6.5
-38 4.7
15.9
16.3
20.8
19.5
NS
NS
.05
,002
5 5 4.5 4.4
.05
NS
.04 .01
3.6 3.9
NS
.005
1.e
NS
&Probability value of orthogonal contrasts. NS = nonsignificant (P > .11. There were no significant interactions.
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48 7 14 21 30 42 56
LACT
FARMER ET AL.
2640
Blood urea was drastically reduced (P .c .001) on d 26 of lactation in LACT sows, whereas globulin (P < .01) and total protein increased (P = .05; Table 5). Albumin decreased (P = .O21 in GEST-LACT gilts (Table 5).
~
A
A
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3rd and 4th wk of lactation. A similar decrease in feed intake was noticed in the 4th wk of lactation in the present trial, but feed intakes of sows from all treatments were lower than in the study of Harkins et al. (1989). This may have counteracted any possible effects of exogenous GRF on milk production, because the greatest increase due to treatment would be expected during that period of Discussion time. The decrease in the a1bumin:globulin ratio observed in LACT sows in the present study In the present study a dose of 12 mg of denotes a protein abnormality that may have been exogenous GRF injected three times daily at the caused by the reduced protein intake. This is end of gestation and(or1 during lactation did not substantiated by the lower blood urea content and increase milk production or alter milk composition higher total protein content. Such results suggest of sows. Whether this lack of effect was due to the a more efficient utilization of protein sources in transient delivery of GRF or to the significant LACT sows, which was sufficient to maintain milk reduction in feed intake during the 4th wk of production, but not to increase it. lactation is not known. The latter explanation Harkins et al. (1989) suggested that the seems most likely. Harkins et al. (19891 observed decreased feed intake in GH-treated sows may be an increase in milk production of sows injected due to alterations in the feedback system that with GH, but feed intake was reduced during the regulates feed intake or to impurity of the hormone preparation. The latter reason may not be the case in the present trial because GRF was produced by chemical synthesis and was purified. The basis for the effect of elevated GH concentrations on feed intake is not clear yet. The decreased 6 feed consumption seen in the present trial could be related to alterations in the system regulating feed intake, such as elevated glucose or FFA concentrations. In sheep, exogenous GRF given to ewes from d 105 to 115 of gestation increased milk yield during the succeeding lactation (Kann et al., 19881, whereas in cattle, prepartum injections of a GRF agonist had no effect on milk production and on calf ADG during the first 2 mo of lactation (Simpson et al., 1989). With regard to sows, immunization against GRF before breeding, which prevented pulsatile release of GH during gestation and lactation, decreased milk production on d 19 of lactation, without affecting growth of pigs (Esbenshade et al., 1989). It is not known whether CTL the immunization exerted its effects on milk 1 GEST via the increased antibody titers production I LACT against GRF during gestation and(or1during lactaI G EST- LACT tion. Moreover, experiments with exogenous GH showed that the increases in milk production observed in sows injected with GH were not higher 2 3 4 WEEK OF LACTATION when the animals were treated during gestation and lactation than when they were treated only during lactation (Spence et al., 1984; Harkins et al., Figure 1. Feed consumption (least squares means) 1989). Cromwell et al. (198913) also found that throughout lactation for gilts injected thrice daily with exogenous GH given during late gestation did not 12 mg of growth hormone-releasing factor(1-29)NHz or increase milk production of lactating sows, and saline (CTL = control) during the last 10 d of gestation Kveragas et al. (1986) observed that exogenous GH (GEST) and(or)lactation (LACT).Values of SEM are .12, given during the last 21 d before farrowing did not .24, .23,and .24 for wk 1 to 4 of lactation, respectively. significantly increase milk volume on d 14 of The probability level is > .1 for wk 1 to 3 and < ,001 lactation. These results corroborate our finding for wk 4.
2641
GRF AND LACTATION IN SOWS
Table 4. Least squares means for growth hormone (GH) variables, insulin-like growth factor I (IGF-I), prolactin (PRL), free fatty acids (FFA), and glucose concentrations in gilts injected thrice daily with 12 mg of growth hormone-releasing factor(1-29)NHZ or saline during the last 10 days of gestation (GEST) and(or) lactation (LACT)"
GEST Item
GEST
LACT
5.7 5.6 8.2 1,779 88.3 44.1 250 5.O
4.8 6.1 9.0 1,912 64.8 36.1 517 4.3
6.0 13.0 33.4 4,149 118.5 38.0 53 1 5.1
5.0 11.8 33.3 3,768 80.7 27.9 512 5.2
X
GEST
LACT
LACT
SEM
NS
.6 1 .o 4.1 332 1.1 5.9 73 .2
.01
.001 .001 .001 .03
NS
NS
NS NS NS NS NS NS
.10
.07 .03
.06 .07
NS NS NS NS
NS
&Blood samples were obtained every 20 min for 8 h on d 26 of lactation. "Probability value of orthogonal contrasts; NS = nonsignificant (P > .I).
that GRF injections during late gestation do not increase milk production of lactating sows. The discrepancy between our results and those obtained with GRF immunization (Esbenshade et al., 1989) may result from the large individual variations in milk production and the small sample size of the latter study (five treated sows vs four controls). Even though positive effects of GH on milk production of sows were reported (Spence et al., 1984; Harkins et al., 1989; Smith et al., 19911, it is still debatable whether GH does have a galactopoietic effect in swine, because other experiments have shown no increase in milk production
of sows injected daily (Cromwell et al., 1989a) or once every 3 d (Crenshaw et al., 1989; Cromwell et al., 1989b) with GH. Biological activity of GRF in the present trial is indicated by the increased GH and IGF-I concentrations seen in sows treated during lactation and by the decreased backfat thickness observed at weaning in these same animals. The increased FFA concentration in treated sows also denotes their negative energy balance and the utilization of body reserves. Unlike GH, which caused the deaths of a number of sows (Kveragas et al., 1986; Cromwell et al., 1989b; Smith et al., 19911, GRF showed no harmful effect on health of lactating
Table 5. Least squares means for milk yield and composition, and urea, total protein, albumin, and globulin content in gilts injected thrice daily with 12 mg of growth hormone-releasing factor(1-29)NHz or saline during the last 10 days of gestation (GEST) and(or] lactation (LACT)" P-value" GEST Item Milk yieldc, kg/d Milk DMd, % Milk fatd, % Milk lactosed, O/O Milk proteind, O h Urea, mmol/L Total protein, g/L Albumin, g/L Globulin, g/L Albumin:globulin ratio
Control
GEST
LACT
GESTLACT
8.5 17.9 8.2 4.9 5.6 8.1 71.5 44.8 28.7 1.139
9.0 18.2 6.3 4.6 5.6 8.7 72.6 47.2 25.4 1.87
9.0 18.7 7.0 4.6 5.7 4.9 75.5 46.4 29.0 1.60
8.7 18.4 6.8 4.6 5.7 4.2 74.1 44.4 29.7 1.52
X
GEST NS NS NS NS NS NS NS NS NS NS
LACT
NS NS .09
NS NS
LACT
SEM
NS NS NS NS
.35 .36 34 .12 .13 .5 1.3 .8 1.1 .07
.0001 .05
NS NS NS
NS
.02
.008 .008
NS NS
&Blood samples collected on d 28 of lactation. "Probability value of orthogonal contrasts; NS = nonsignificant (P > .1). d 24 of lactation. d 25 of lactation.
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GH preinjection, ng/mL Mean GH, ng/mL GH peak, ng/mL GH area under the curve, ng.rnin-'.mL-l IGF-I, ng/mL Mean PRL, ng/mL FFA, mEq/L Glucose, mmol/L
Control
GESTLACT
FARMER ET AL.
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Implications Treatment of sows with exogenous growth hormone-releasing factor did not increase their milk yield or improve litter performance, most likely because of the decreased feed intake of treated sows during lactation. To assess the full potential of growth hormone-releasing factor for lactating sows, the nutrient requirements of sows with increased milk production must be assessed and a better understanding of the factors that regulate feed intake in sows with elevated growth hormone concentrations must be achieved.
Literature Cited Abramowitz, M., and I. A. Stegun. 1972. Handbook of Mathematical Functions. M. Abramowitz (Ed.). Dover, New York. AOAC. 1980. Official Methods of Analysis (13th Ed.).Association of Official Analytical Chemists, Washington, DC. Crenshaw, T. D., C. M. Grieshop, J. P. McMurtry, and B. R. Schricker. 1989. Exogenous porcine prolactin and somatotropin injections did not alter sow lactation performance. J. Anim. Sci. 67(Suppl. 1):258 (Abstr.1. Cromwell, G. L., T. S. Stahly, L. A. Edgerton, H. J. Monegue, T. W. Burnell, B. C. Schenck, and M. K. Dunlap. 1989a. Weekly administration of recombinant porcine somatotropin to lactating sows. J. Anim. Sci. 67(Suppl. 1):258 LAbstr.1. Cromwell, G. L., T. S. Stahly, L. A. Edgerton, H. J. Monegue, T. W. Burnell, B. C. Schenck, and T. T. Elkins. 1989b. Recombinant porcine somatotropin for lactating sows. J. Anim. Sci. 67(Suppl. 1):257 (Abstr.). Dubreuil, P., G. Pelletier, D. Petitclerc, H. Lapierre, Y.Couture, P. Gaudreau, J. Morisset, and P. Brazeau. 1990a. Influence
of growth hormone-releasing factor and(or) thyrotropin-releasing factor on sow blood components, milk composition and piglet performance. Can. J. Anim. Sci. 70:821. Dubreuil, P., D. Petitclerc, G. Pelletier, P. Gaudreau, C. Farmer, T. F. Mowles, and P. Brazeau. 199Ob. Effect of dose and frequency of administration of a potent analog of human growth hormone-releasing factor on hormone secretion and growth in pigs. J. h i m . Sci. 68:1254. Esbenshade, K. L., J. D. Armstrong, M. T. Coffey, and C. A. Bowie. 1989. Reproductive performance of sows actively immunized against growth hormone-releasing factor (GRF). J. h i m . Sci. 67(Suppl. 1):197 L4bstr.l. Farmer, C., P. Dubreuil, G. Pelletier, D. Petitclerc, and P. Brazeau. 1990. Active immunization against somatostatin in gestating gilts and the effect of transferred immunity on piglets. Can. J. Anim. Sci. 70:211. Ford, J. J.,and R. R. Maurer. 1978. Simple technique for chronic venous catheterization of swine. Lab. Anim. Sci. 28:615. Harkins, M., R. D. Boyd, and D. E. Bauman. 1989. Effect of recombinant porcine somatotropin on lactational performance and metabolite patterns in sows and growth of nursing pigs. J. Anim. Sci. 67:1997. Kann, G., A. PBrier, and J. Martinet. 1988. Use of human growth hormone-releasing factor hGRF 1-29)NHz as a mammotropic hormone in the ewe. J. Anim. Sci. 66(Suppl. 1):389 (Abstr.). Kveragas, C. L., R. W. Seerley, R. J. Martin, and W. L. Vandergrift. 1986. Influence of exogenous growth hormone and gestational diet on sow blood and milk characteristics and on baby pig blood, body composition and performance. J. Anim. sci. 63:1877. Lewis, A. J., V. C. Speer, and D. G. Haught. 1978. Relationship between yield and composition of sow’s milk and weight gains of nursing pigs. J. Anim. Sci. 473334. Noblet, J., and M. Etienne. 1989. Estimation of sow milk nutrient output. J. Anim. Sci. 67:3352. Robert, S., A.M.B. de PassillB, N. St-Pierre, P. Dubreuil, G. Pelletier, D. Petitclerc, and P. Brazeau. 1989. Effect of the stress of injection on the serum concentrations of cortisol, prolactin, and growth hormone in gilts and lactating sows. Can. J. Anim. sci. 69:663. SAS. 1982. SAS User’s Guide: Statistics. SAS Inst. Inc., Cary, NC. Simpson, R. B., J. D. Armstrong, and R. W. Harvey. 1989. Effect of prepartum administration of a growth hormone releasing factor agonist on growth hormone, milk production and interval to ovarian activity in primiparous beef heifers. J. h i m . Sci. 67(Suppl. 11:331 (Abstr.). Smith, V. G., A. D. Leman, W. J. Seaman, and F. VanRavensw a y . 1991. Pig weaning weight and changes in hematology and blood chemistry of sows injected with recombinant porcine somatotropin during lactation. J. Anim. Sci. 69: 350 1.
Spence, C. A,, R. D. Boyd, D. E. Bauman, W. R. Butler, and C. D. Wray. 1984. Effect of exogenous growth hormone on fetal energy storage and lactation performance in sows. J. Anim. Sci. 59(Suppl. 1):246 (Abstr.).
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sows. The reason for this difference is not clear but may be related to hormonal preparation. We can conclude, therefore, that exogenous GRF given during gestation has no beneficial effect on performance of lactating sows and their litters. However, sows receiving GRF during lactation may utilize protein more efficiently, enabling them to maintain their milk production and litter performance in spite of a decreased feed intake. Therefore, the nutritional requirements of animals receiving such treatments would have to be reevaluated to determine the real potential of GRF for lactating sows.
