Reproduction Abstracts

Introduction: The continued decline in fertility is a multifactorial problem and has severe adverse impact on a farm’s profitability. Under-nutrition during pregnancy can subsequently affect the cardiovascular system, renal function and fertility in the offspring. This study tested the hypothesis that maternal protein restriction would adversely affect fetal ovarian development and number of germ cells.

Methods: Fourteen Scottish Blackface ewes were fed either control (CP n=6) or low protein diet (LP n=8 17 vs 8.7 g crude protein/MJ metabolisable energy) from conception to day 65 of gestation when the ewes were euthanised. Fetal ovaries were weighed, fixed in Bouin’s and paraffin-embedded. Sections (5 μm) were subjected to histological and immunohistochemical analysis for the oogonia/oocyte markers: OCT4, DAZL and VASA. The oogonia/oocyte counts were determined by image analysis and groups compared by t-test.

Results and discussion: Fetal ovaries tended to be smaller in the LP (201.2 mg) versus CP (252.6 mg) diet (P=0.08). There was no difference in ovarian histological morphology between the two groups. There was an abundance of OCT4, DAZL and VASA-positive cells in the fetal ovarian cortex on day 65 of gestation. The numbers of OCT4, DAZL, and VASA-positive cells within the ovigerous cords was similar in both dietary groups (P>0.05). Furthermore, the estimated total number of OCT4, DAZL, and VASA-positive cells in the whole fetal ovary were unaffected by maternal diet (P>0.05). OCT4-positive cells were more abundant than DAZL (P<0.01), which was 2-fold more abundant than VASA-positive cells (P<0.001), suggesting germ cell development was occurring at this time. However, the ratios between different germ cell markers was the same across the different diets (P>0.05). In conclusion, there is no evidence that on day 65 of gestation the gross fetal ovarian structure or number of germ cells were influenced by dietary protein restriction in sheep.

Funded by TETFUND, Nigeria.