Meeting Abstract

P1.223  Friday, Jan. 4  High dose testosterone causes oocyte reabsorption in chickens NAVARA, KJ*; PINSON, SE; LITTLE, T; The University of Georgia; The University of Georgia; The University of Georgia knavara@uga.edu

It has been shown that hormones, including testosterone and corticosterone, influence offspring sex when given during a very critical window surrounding ovulation in birds. One of the potential mechanisms posited for this influence is that females may preferentially discard oocytes of the unwanted sex before fertilization and development can occur. It is known, particularly in the poultry industry, that even in normal reproductive hens, a small percentage of oocytes are ovulated into the peritoneal cavity rather than the infundibulum of the reproductive tract, a phenomenon called oocyte reabsorption. It is not known, however, to what extent testosterone and corticosterone exert control over the process of oocyte reabsorption in chickens. We treated hens with pharmacological doses of testostosterone and corticosterone as well as a control vehicle 5h prior to ovulation and monitored egg-laying behavior in all treated hens as well as a set of hens that went untreated. Significantly more testosterone-treated hens failed to lay the egg that would have been ovulated compared with control, corticosterone-treated, and untreated hens. We then killed and dissected a subset of hens from the testosterone group that laid (n=10) or failed to lay (n = 18) as well as hens that failed to lay from the corticosterone and control groups (n = 9) and untreated hens that laid eggs at the time the treated hens were expected to lay (n = 11). Ruptured yolks lined the peritoneal cavities of 11 of 18 testosterone-treated hens that did not lay eggs, while only three out of all 47 remaining hens had yolk in the peritoneal cavity. These results suggest that high-dose testosterone causes oocyte reabsorption, perhaps by uncoupling the infundibulum from the ovary. The next step is to examine whether oocytes are reabsorbed in a sex-specific manner.