Luteinizing hormone in nutrient-restricted ovariectomized ewes2

Abstract

Abstract This study was designed to evaluate profiles of serum concentrations of LH, pituitary content of LH and GnRH receptors, and hypothalamic content of GnRH in undernourished, ovariectomized ewes. In earlier studies, pulsatile secretion of LH diminished as duration of undernutrition progressed in prepubertal or adult ovariectomized ewes. Ewes having similar body condition scores (CS) of 5 to 9 (1 = extremely thin, 5 = moderate, 9 = obese) were fed maintenance or low-energy diets (100% and 60% of NRC requirements, respectively). Blood samples for analysis of LH were collected at 15-min intervals for 4 h at initiation of the project and immediately prior to slaughter. Serum concentrations of LH did not differ (P > .05) among groups at the initial sampling period. At slaughter, ewes with CS ≤ 2 (n = 7) had lost 26.8 kg (42% of initial weight). Ewes with CS ≥ 3 (n = 12) had lost an average of 13.7 kg (18% of initial weight). Concentrations of LH in ewes with final CS ≥ 3 was similar (P > .05) to that observed during the initial sampling period. However, release of LH was reduced (P < .01) in ewes with CS ≤ 2 compared with ewes with CS ≥ 3 (2.6 vs 9.5 and 3.2 vs 10.5 ng/ml for basal and mean concentrations, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)