A bovine model to study reproductive aging

Abstract

Decline in fertility with age has been well documented in women. There are ethical limitations to use humans as a model for basic research, and there is a lack of well characterized animal model. The objective was to characterize and validate a bovine model for the study of age-associated subfertility. All experiments were conducted on the same group of 13-14 year old cows (n=10), and their 1-4 year old young daughters (n=10). Mother-daughter pairs were used to reduce genetic variations. Follicular wave pattern in a natural reproductive cycle was maintained in old cows similar to that in daughters. We hypothesized that aging in cattle is associated with elevated circulating concentrations of FSH, and reduced concentrations of steroid hormones. As stated, circulating FSH concentrations were higher (P=0.009) during follicular waves in old than young cows. The ovulatory follicle in 2-wave cycles was smaller in old cows (P=0.04), but plasma estradiol concentrations were higher (P=0.01). Luteal phase progesterone tended to be lower in old than young cows (P=0.1). The number of 4-5 mm follicles recruited into a follicular wave was lower (P