56.6 Thursday, Jan. 6 Elevated testosterone during meiotic segregation stimulates laying hens to produce more sons. PINSON, SE*; NAVARA, KJ; University of Georgia, Athens; University of Georgia, Athens firstname.lastname@example.org
Birds have demonstrated a remarkable ability to manipulate offspring sex. Previous studies suggest that treatment with hormones can stimulate females to manipulate offspring sex, and that this effect occurs before the oocyte is even ovulated. For example, acute and chronic treatments with testosterone stimulated significant skews towards male offspring. It has been suggested that hormones may act by influencing which sex chromosome is donated by the heterogametic female bird into the ovulated ovarian follicle. However, it is difficult to pinpoint when the effects of testosterone on offspring sex occurred in previous experiments because these testosterone treatments were given either chronically over the entire period of follicular development or many hours before the critical period of chromosome segregation. We treated laying hens with testosterone injections 5h prior to ovulation to target this critical period and quantified the sexes of the subsequently ovulated eggs. We hypothesized that an injection of testosterone coincident with segregation of the sex chromosomes would stimulate hens to produce more male than female offspring. As hypothesized, hens injected with testosterone produced a significant bias towards male offspring compared to controls, nearly 70% (p=0.05). These results suggest that acute testosterone elevation during meiotic segregation may mediate skews in primary sex ratios by female birds.