The effects of short-term nutritional stimulus before and after the luteolysis on metabolic status, reproductive hormones and ovarian activity in goats.

The effect of short-term nutritional supplementation on hormonal and ovarian dynamics was studied in goats. Cycling Shiba goats were divided randomly into maintenance (group M, n=4) and high-energy (group H, n=4) groups. After the detection of the ovulation (Day 0, 1(st) ovulation), group H received a high-energy diet providing 2.5 times of the maintenance energy requirement for 7 days from Day 7 to Day 13 and were administered 2 mg of prostaglandin F(2alpha) (PGF(2alpha)) on Day 10 to induce luteal regression followed by the follicular phase. Follicular and luteal dynamics were monitored using ultrasonography daily or every other day, and blood samples were collected daily from Day 0 to the third ovulation (3(rd) ovulation) following the second ovulation (2(nd) ovulation) induced by PGF(2alpha) administration. Blood samples were also collected at 10-min intervals for 6 h on Day 9 and Day 11 for analysis of pulsatile LH secretion. The mean concentrations of glucose and insulin were significantly (P<0.05) higher in group H than in group M on Days 8, 9, 12, 13 and Days 8, 9 and 10, respectively. For both the 2(nd) and 3(rd) ovulations, no significant difference was detected in ovulation rate between groups M and H. On the other hand, the interpeak interval for wave-like patterns of FSH in group H was significantly (P<0.05) shorter than in group M during the period between the 1(st) and 2(nd) ovulations (4.3 +/- 0.3 vs. 6.5 +/- 1.5 days). The mean LH pulse frequency in group H was significantly (P<0.05) greater than in group M on Day 11 (4.5 +/- 0.6 vs. 3.3 +/- 0.5 pulses/6 h). The present study clearly demonstrated that short-term (7 days) nutritional supplementation promoted pulsatile LH and wave-like FSH secretions in cycling goats. However, no significant increase in ovarian performance was found under such endocrine and metabolic conditions.