
%0 Journal Article
%A Landau, S 
%A Houghton, JA 
%A Mawhinney, JR 
%A Inskeep, EK 
%T Protein sources affect follicular dynamics in ewes near the onset of the breeding season
%J Reproduction, Fertility and Development
%D 1996/10/01
%V 8
%N 6
%P 1021-1028
%K 
%R https://doi.org/10.1071/RD9961021
%U https://www.publish.csiro.au/paper/RD9961021 
%X 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 F2 alpha (PGF2 alpha). 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 > or = 2 mm in diameter were observed on the ovaries of ewes fed SBM four days before PGF2 alpha treatment (P < 0.02), but the highest number was seen in ewes fed CGM-GC at the time of injection of PGF2 alpha (P < 0.08). Ewes fed SBM had larger follicles at last detection and ovulated earlier after PGF2 alpha 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 PGF2 alpha 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. 
