Effects of administration of growth hormone-releasing factor to sows during late gestation on growth hormone secretion, reproductive traits, and performance of progeny from birth to 100 kilograms live weight.

The effects of growth hormone-releasing factor (GHRF) injections to sows during late gestation were investigated in two experiments. In the first one, four treatments were applied to eight catheterized sows according to two 4 x 4 Latin squares: oral administration of 2 mg of pyridostigmine, a cholinesterase inhibitor, per kilogram of BW (PYR group); i.m. injection of 50 micrograms of GHRF/kg BW (GHRF group); a combination of the pyridostigmine and GHRF treatments (PYR+GHRF); or i.m. injection of glucose (control). Pyridostigmine slightly increased the plasma concentration of growth hormone (GH). Growth hormone responses to GHRF and PYR+GHRF treatments were similar, with significantly elevated GH concentrations from 5 to 240 min after GHRF injection. In the second experiment, 36 sows were allocated to two treatments at 102 d of gestation. Until farrowing, they were injected twice daily with 50 micrograms of GHRF/kg BW (GHRF group) or isotonic glucose (control). The DM, N, fat, and energy content of 24 pigs per group was determined at weaning at 22 d. Six pigs per litter had ad libitum access to feed until slaughter at 100 kg BW and their carcasses were evaluated. Treatment with GHRF increased pregnancy duration (114.8 vs 113.6 d, P less than .05), weight of pigs at 13 d (3.69 vs 3.54 kg, P less than .05) and at weaning (5.74 vs 5.48 kg, P less than .05), and improved pig survival (86 vs 71%, P less than .05). Lipid (on a DM basis) and energy contents of the pigs slaughtered at weaning were significantly higher in the GHRF group than in the control group (14.4 vs 12.5% and 2,178 vs 2,029 kcal/kg, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)