Cyclic changes in bovine vesicular follicles.

K N O W L E D G E of the normal quantitative cyclic changes in the ovarian follicular system would be a meaningful aid in assessing the influence of exogenous agents on the ovary. Previous reports on cyclic changes in bovine vesicular follicles (Hammond, 1927: Cole, 1930; McNutt , 1927: Cupps et al., 19,59; Hansel, 1959) were based on gross counts, or study of the largest follicle in isolated sections. Rajakoski (1960) made an intensive study of the quantitative variations in bovine vesicular follicles during the estrous cycle: however, follicles tinder 1.0 ram. were not included. Erickson (1966), after a detailed study of follicles of all sizes in postnatal bovine ovaries, reported that the number of normal vesicular follicles generally equals or exceeds the number of atretic follicles in ovaries from cows tip to 10 years of age. No effort was made to determine different proportions of these follicles in various phases of the reproductive cycle. Systematic quantitative study of bovine vesicular follicles during pregnancy has not been reported. The present study was an effort to identify cyclic changes in vesicular follicles during normal estrous cycles and pregnancy.