LACTATION PERFORMANCE OF SOWS FED A BULKY DIET DURING GESTATION AND RECEIVING GROWTH HORMONE-RELEASING FACTOR DURING LACTATION

Forty-eight crossbred gilts were used in an experiment with a 2 x 2 x 2 factorial arrangement of treatments. Treatments were control or bulk y diet during gestation (4.1 vs 15.3% crude fiber), number of meals se rved daily in lactation (2 vs 4), and three daily s.c. injections of s aline or of 1 mg of a human growth hormone-releasing factor analog (GR F-AN) from d 3 to 29 of lactation. Weights of pigs were recorded weekl y until weaning on d 33. On d 29 of lactation, milk yield was estimate d and a milk sample was obtained the next day. Jugular blood samples w ere collected from the sows on d 3 and 28 of lactation. Feed and water intake of sows were recorded throughout the study. Feeding the bulky diet decreased water intake in gestation (P < .001) and increased feed intake in lactation (P < .03). The number of meals served daily had n o effect on feed intake during lactation (P > .1). Injections of GRF-A N increased IGF-I concentrations in blood (P < .01) and in milk (P < . 001) and decreased backfat thickness (P < .001) and feed intake (P < . 001) of sows during lactation. Pigs from sows injected with GRF-AN wei ghed more on d 14 (P < .05) and had a tendency to weigh more on d 7 (P = .09) and d 21 (P = .06). The incidence of sows showing estrus withi n 10 d of weaning was reduced with exogenous GRF (P < .01). The use of exogenous GRF in lactating sows may therefore have beneficial effects on growth of the pigs, yet the optimal nutritional and hormonal. cond itions needed for GRF to exert its full potential still need to be det ermined.