Co-Authors:
Landau, S., Sheep and Coats Department, Extension Service, Ministry of Agriculture, P.O. Box 7054, Hakirya, Tel Aviv, Israel
Houghton, J.A.S., Department of Animal and Veterinary Science, West Virginia University, P.O. Box 6108, Morgantown, WV, United States
Mawhinney, J.R., Department of Animal and Veterinary Science, West Virginia University, P.O. Box 6108, Morgantown, WV, United States
Inskeep, E.K., Sheep and Coats Department, Extension Service, Ministry of Agriculture, P.O. Box 7054, Hakirya, Tel Aviv, Israel
Abstract:
The influence of source of protein during the luteal phase before a synchronized oestrus on the dynamics of follicular development, observed daily by ultrasonography, was assessed in ewes that were beginning the sexual season. Iso-nitrogenous amounts of soybean meal (SBM) or of a corn-gluten meal-ground-corn grain mixture (CGM-GC), or an iso-energetic amount of ground-corn grain (GC), were fed from four days before to four days after treatment with prostaglandin F(2α) (PGF(2α). Feeding with SBM was associated with a higher frequency of short luteal phases (P < 0.02). Dynamics of follicular population were studied in ewes that ovulated after normal cycles. More follicles ≤ 2 mm in diameter were observed on the ovaries of ewes fed SBM four days before PGF(2α), treatment (P < 0.02), but the highest number was seen in ewes fed CGM-GC at the time of injection of PGF(2α), (P < 0.08). Ewes fed SBM had larger follicles at last detection and ovulated earlier after PGF(2α), treatment than their counterparts fed other diets (P < 0.001). Ovulatory follicles developed over a greater range of days in ewes with twin ovulations compared with ewes with single ovulations (P < 0.08). Serum concentrations of insulin were increased after four days of feeding with CGM-GC (P < 0.01), but not with SBM or GC, and reached a peak at the time of oestrus. In summary: (1) the source of dietary protein during the late-luteal phase affected follicular maturation after PGF(2α), treatment; (2) insulin and glucose may be involved in this response and may play a role in ovarian follicular activity; and (3) twin ovulations appeared to result from both reduced atresia and increased recruitment of follicles.