Enhancement of Ovulatory Follicle Development in Maiden Sheep by Short-term Supplementation with Steam-flaked Corn

Abstract

The effect of a short-term nutritional supplementation with steam-flaked corn on metabolism and folliculogenesis was evaluated in 14 maiden sheep. Oestrus was synchronized with two prostaglandin F(2alpha) doses given 10 days apart. From day 11 to 15 of the oestrous cycle induced with prostaglandins, half of the ewes (group 2M) were supplemented with steam-flaked corn, double the daily maintenance ration of the control sheep (group 1M). Body weight and condition remained unaffected, but the energetic supply increased plasma concentrations of glucose (3.6 +/- 0.1 vs 4.3 +/- 0.1 mmol/l, p < 0.0001) for the first 4 days and 3-hydroxybutyrate (0.323 +/- 0.58 vs 0.582 +/- 0.04 mmol/l, p < 0.005) from day 2 to 4. The profile of insulin secretion was also affected by the treatment, increasing in group 2M to reach significant differences on days 13 and 14 (p < 0.05). From similar values at the start of the food supply, the treatment induced a higher follicular development in group 2M (1.1 +/- 1.2 vs 7.4 +/- 1.06 total follicles in day 15, p < 0.05), as evidenced by the lineal increase in the number of larger follicles (>4 mm, p < 0.005). Then, the number of follicles >4 mm in size in 2M was around 60% higher on day 16 (7.86 +/- 0.45 vs 4.86 +/- 0.63, p < 0.005). Thereafter, the mean number of corpora lutea per ewe was around 30% higher in group 2M (1.43 +/- 0.2 vs 1.10 +/- 0.1, although differences were not found to be statistically significant). These data suggest that the use of diets containing high starch sources, like the steam-flaked corn, increases folliculogenesis and ovulation rate in sheep and can be applied in short-term feeding practices.