Characteristics of Small Antral Follicles in Heifers Carrying the Bovine High Fecundity Allele Trio

Trio, a bovine high fecundity allele, results in ovarian antral follicles that develop at a slower rate, acquire ovulatory capacity at smaller sizes, and have a 3-fold greater ovulation rate. Results from recent research indicate that, after primordial follicle activation, follicles in Trio carriers have slower progression through the primary stage. However, the effect of the Trio allele on small antral follicles remains unknown. Thus, the objective of the present study was to compare the morphological characteristics of small antral follicles of Trio carrier and non-carrier cattle. Ovarian tissue from Trio carrier (n=9) and non-carrier heifers (n=6) was collected, fixed, and paraffin embedded. Six sections of each ovary were stained with hematoxylin-eosin and evaluated under a bright field microscope. Small antral follicles (0.3) in granulosa cell layer area (130,614±13,039 µm^2), antrum area (50,314±7,677 µm^2), or oocyte area (8,000±610 µm^2) between Trio carrier and non-carrier follicles. The percentage of the total follicle area occupied by the antrum (22.8% ± 1.6) or the granulosa cell layer (71.5%±1.3) was not different (P>0.20) between gentoypes. There was, however, a tendency (P=0.07) for the oocyte to occupy a larger percentage of the follicle area in Trio carrier (6.3%±0.8) than non-carrier (4.1%±0.6) follicles. In conclusion, presence of the Trio allele does not affect the morphological characteristics of small antral follicles.Will C. Hauk Endowment fund to The Ohio State University College of Food, Agricultural, and Environmental SciencesNo embargoAcademic Major: Animal Science