Relationship between ovarian Follicles and Peripheral Levels of Sex Steroid Hormones during Early Midpregnancy in Cows

Abstract

A transrectal real-time ultrasound scanner was used to study the structures of the ovaries during early midpregnancy in cows. The serum concentrations of sex steroids between cows with large and small or no follicles in the ovaries were not significantly different. The presence of large follicles in the ovaries was not consistently associated with an increase in serum estrogen levels and did not have a luteolytic effect on the corpus luteum of pregnancy. The changes in the serum concentration of sex steroids before and after the puncture of large follicles in the ovaries of 4 pregnant cows were also examined, together with six steroids concentration in the follicular fluid. The findings suggest that although large follicles are present in the ovaries of cows during midpregnancy, they do not significantly contribute to peripheral levels of sex steroids.