NUTRITIONAL MANIPULATION OF GROWTH AND METABOLIC AND REPRODUCTIVE STATUS IN PREPUBERTAL GILTS

Reproductive status, metabolic state, and carcass composition were com pared in prepubertal littermate gilts of 85 kg BW and identical ages a fter allocation to one of two feeding regimens at 75 kg, either twice- daily feeding to appetite up to 85 kg and then maintenance feeding unt il slaughter (Group 85AR) or an initial period of maintenance feeding at 75 kg and then feeding to appetite to reach 85 kg (Group 85RA). Oth er littermates were studied at the start of treatment (Group 75C) and after the initial period of feeding to appetite (Group 85A) or mainten ance feeding (Group 75R). In the absence of differences in backfat dep th or longissimus muscle area, Group 85RA gilts showed increased folli cular development (P <.001) compared with their feed-restricted Group 85AR littermates. Plasma LH (P <.001) and FSH (P <.02) responses to an LHRH challenge differed between these same groups. Feed restriction r educed preprandial glucose, postprandial cortisol, and insulin(P <.05) , total plasma IGF-I, and basal and postprandial free triiodothyronine (T-3; all P <.001) at all stages of the experiment. Postprandial insu lin, pre-(P <.001) and postprandial free T-3, and plasma IGF-I (P <.00 1) increased in response to refeeding (Group 75R vs 85RA). These data indicate that changes in metabolic status can mediate shortterm nutrit ional effects on reproductive function, in the absence of changes in a ge, weight, and widely used indices of body composition, and also esta blish the short-term, feed-restricted, prepubertal gilt as an effectiv e model for studying the mechanisms mediating nutrition-reproduction i nteractions.