Our current reproductive work focuses on the mechanisms of ovarian follicle selection in cattle. Specifically, we are investigating the roles of the insulin-like growth factor (IGF) system in the mechanisms of follicle growth. Ovarian follicles grow throughout the oestrous cycle of cattle. During the luteal phase, there are up to 2 sequential non-ovulatory waves of follicle growth and during the follicular phase the ovulatory wave grows and produces the ovulatory follicle. Growth of a follicle wave involves emergence of a cohort of 4 to 20 follicles, selection down to the ovulatory quota (usually one follicle in cattle); dominance during which the selected follicle continues growing and suppresses the growth of subsequent follicles, and atresia (in the luteal phase) or ovulation (in the follicular phase). The end of dominance, signified by either atresia or ovulation, allows a subsequent wave of follicles to grow. These waves of follicle growth are tightly regulated by transient increases in follicle-stimulating hormone (FSH). However, the mechanism by which selection occurs during declining FSH concentrations remains a subject of intense research. Clearly it has been demonstrated by both our research and that of others that increased bioavailability of IGF-I, facilitated by decreased IGF-binding protein (IGFBP) activity, is involved. Our recent work has studied the roles of both proteolysis on the IGFBPs and their gene expression.

In the area of stress physiology in cattle, using surgical and burdizzo castration as acute stressors, we have studied the roles of non-steroidal anti-inflammatory drugs (NSAIDs) in the mediation of stress-induced changes in the hypothalamus-pituitary-adrenal axis and immune function responses. Currently, our focus is on the identification of key inflammatory genes involved with the inflammatory responses of bull calves following castration. Ketoprofen (Ketofen) was successful in suppressing cortisol secretion and blocking immune suppression following castration of cattle.