The effect of short-term lupin (Lupinus angustifolius) feed supplementation on serum steroid hormones, insulin-like growth factor I, and ovarian follicular development and atresia in Merino ewes

Abstract

The effects of short-term lupin supplementation on ovulation rate in ewes during oestrous season are well known. In this study, we tested the effects of an 8-day lupin supplementation on folliculogenesis during anoestrus applied over the hormonal treatment of ewes. Fourteen anoestrous Merino ewes were assigned into 2 groups (n = 7 for each) in which the control group was fed a basal diet and the experimental group was supplemented with lupin groats (500 g per head per day). Both groups were treated intramuscularly with 12.5 μg/head lecirelinum (luteinising hormone releasing hormone super analogue) on the first day of supplementation and 5 days later with 37.5 μg/head cloprostenolum D (prostaglandin F2α analogue). Serum sexual steroid and insulin-like growth factor I (IGF-I) concentrations were assessed using radioimmunoassay and enzyme-linked immunosorbent assay methods, respectively. Folliculogenesis was evaluated using a light microscope. Lupin feeding did not affect progesterone or IGF-I, but it significantly decreased the concentration of oestradiol-17β. Lupin significantly increased the number of follicles of 3-5 mm in diameter and the total rate of atresia. The follicles mainly collapsed and underwent late atresia. The size of healthy and collapsed follicles increased in the lupin-fed group. These results indicated that 8-day lupin supplementation affected follicular development and atresia through an IGF-I/oestradiol feedback system.