Abstract. 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 F2α (PGF2α) 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 PGF2α 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. Key words: Follicle stimulating hormone (FSH), Goat, Luteinizing hormone (LH), Nutritional stimulus, Ovarian activity (J. Reprod. Dev. 55: [39][40][41][42][43][44] 2009) t is well known that nutritional manipulation modulates ovarian functions such as follicular development and ovulation rate in polyovular domestic animals including ewes [1], gilts [2], and goats [3]. There have been several reports of increases in ovulation rate in ewes treated with short-term dietary supplementation of lupin grain, such as for 4 [4], 7 [5], or 11 [6] days during the estrous cycle. Although the nutritional condition in domestic animals has been recognized as a key determinant of reproductive performance, the stimulatory effect of nutritional supplementation on reproductive function remains equivocal. In a recent report that contradicts the above studies, short-term nutritional stimulation of ewes with corn grain and soybean meal during the luteal phase did not increase their ovulation rate [7]. Previous studies have demonstrated that the pattern of daily follicle stimulating hormone (FSH) secretion is wave-like in ewes [8] and goats [9]. There are contradictory results regarding the relationship between ovu...
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