Lactation performance of sows injected with growth hormone-releasing factor during gestation and(or) lactation
1992
Farmer, C. | Petitclerc, D. | Pelletier, G. | Brazeau, P.
Fifty-two Yorkshire X Landrace gilts were equally allotted to four treatments: 1) controls, saline injections (CTL); 2) injections of 12 mg of growth hormone-releasing factor (GRF) (1-29)NH2 thrice daily (0700, 1500, and 2300) from d 100 of gestation until parturition (GEST); 3) injections of GRF thrice daily from d 3 to 29 of lactation (LACT); 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 +/- 1 pigs. Weights of the pigs were recorded weekly from birth (< 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 at weaning also were recorded. On d 24 of lactation, milk yield was estimated by the weigh-suckle-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 1200) was obtained on d 29. Daily feed consumption of sows was recorded 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(or) LACT (P < .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 > .1). Mean growth hormone (GH) concentrations, area under the GH curve (P < .01), and insulin-like growth factor I concentrations (P < .05) were increased in sows treated with GRF during lactation. A reduction in daily feed consumption during the 4th wk of lactation (P < .01) also was observed in LACT sows (average = 4.5 vs 5.4 kg, SEM = .2) compared with 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.
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