Prof. David Wolfenson

Researcher interests: My research centers on reproduction in the dairy cow. I focus on the two major stresses affecting reproduction and fertitliy of cows - environmental heat stress and pathogenic stress. Regarding heat stress, we characterized impairments of follicular and luteal functions related to steroidogeneis, attenuation of follicular dominance and other preovulatory follicle-related functions. Regarding subclinical, chronic mastitis, we found that 1/3 of mastitic cows exhibited delayed ovulation. This syndrome involves disruption of follicular steroidogeneis, low gene expression in theca and granulosa cells and low and delayed LH surge. Attepts to improve fertility of subclinical mastitic cows are currently examined. We found that small early antral follicles are susceptible to long-term, exposure to minimal doses of both Gram-positive and Gram-negative toxins, and the induced damage is then carried over to the preovulatory follicles, corresponding well with the long-term chronic nature of subclinical mastitis. We also found lack of association between clinical mastitic events and premature induction of luteal regression, suggesting that the main cause of low fertility caused by E. coli mastitis post-AI is directed at the embryo rather than the corpus luteum.