ENDOCRINE AND METABOLIC RESPONSES TO REALIMENTATION IN FEED-RESTRICTED PREPUBERTAL GILTS - ASSOCIATIONS AMONG GONADOTROPINS, METABOLIC HORMONES, GLUCOSE, AND UTEROOVARIAN DEVELOPMENT

Temporal relationships among plasma LH, FSH, metabolic hormones, and g lucose concentrations were studied in nutritionally manipulated prepub ertal gilts. Twenty-four growth-matched littermate gilts (73.6 +/- 1.2 kg) were fed at maintenance for 7 d (d 1 to 7), From d 8 to 14, litte rmates were divided between two treatments and were either fed twice d aily to appetite or continued on feed restriction. Feeding to appetite increased episodic LH secretion during the first 6 h of sampling on d 8 (P < .05). Plasma FSH concentrations were not affected by treatment between d 8 and 14. Nocturnal increases in plasma LH (P < .01) and FS H (P < .002) concentrations were detected in feed-restricted gilts but not realimented gilts. Mean total plasma IGF-I concentrations gradual ly increased in gilts fed to appetite (d 12, P < .02; d 13 to 14, P < .001). Mean postprandial insulin concentrations were also greater in g ilts fed to appetite (P < .01). Treatment differences in mean postpran dial glucose concentrations on d 9 and 10 indicate that normoglycemia was established by d 9 in gilts fed to appetite. At slaughter on d 15, numbers of ovarian follicles (P < .01), follicular volume (P < .001), and uterine weight (P < .05) were greater in gilts fed to appetite, I n conclusion, uteroovarian responses to realimentation after short-ter m feed restriction in prepubertal gilts are mediated by enhanced LH se cretion. This rapid enhancement of LH secretion in response to dietary repletion might have been mediated by changes in glucose and insulin status. Ovarian responses to gonadotropins may also be potentiated by observed increases in plasma glucose, insulin, and IGF-I. During feed restriction, a distinct diurnal rhythm in gonadotropin secretion was e vident.