Protein supplementation, body condition and ovarian activity in goats -Pre-ovulatory serum profile of insulin

This study evaluated the effect of level of by-pass protein supplementation (PSL) and body condition (BC) on ovarian activity and serum insulin (INS) concentrations on does. Does (n = 32, 19 mo.) with either a low BC (LBC = 2.1 ± 0.3; n = 16; 28.8 ± 0.72 kg body weight, BW), or a high score (HBC = 3.2 ± 0.3; n = 16, 35.1 ± 0.72 kg body weight) received one of two levels of protein supplementation: Without supplemental protein (NPROT) or 120 g protein as blood meal/d (PROT) during a 40-d pre-ovulatory period. Once oestrous was synchronized, blood samples were collected during the mid-follicular phase at 60 min intervals during a 6-h period, to quantify serum INS concentration. During the late luteal phase (postovulation), total ovarian activity (TOA) was evaluated by transrectal ultrasonographic scanning, counting the total number of follicles (FT) and corpus lutea (CLT). While the HBC group had significantly more CLT than the LBC (2.81 ± 0.20 vs. 1.87 ± 0.20, respectively), no differences occurred between BC groups with respect to FT (2.43 ± 0.25 vs. 2.18 ± 0.25). While PSL affected CL and FT, favouring the PROT-goats (2.62 ± 0.21 vs. 2.06 ± 0.21, and 2.68 ± 0.25 vs. 1.92 ± 0.17, respectively), the HBC goats had significantly higher serum INS levels than the LBC group (1.92 ± 0.17 vs. 0.81 ± 0.17 ng/mL, respectively). The protein supplemented goats also displayed an increased serum INS concentration compared to the non-supplemented goats. A positive correlation was observed between serum INS concentrations and CLT (r = 0.46) and FT (r = 0.38) concentrations. Both the static effect (live weight body condition) and the dynamic effect (by-pass protein supplementation) of nutrition promoted a metabolic status characterized by high insulin levels and an increased ovarian activity.