Acute prenatal androgen treatment increases birth weights and growth rates in lambs.

One hundred seventy-four Border Leicester x Merino ewes were mated to Romney Marsh rams. The ewes were randomly allocated to either an untreated control group or to one of four treatment groups. The treated groups were defined by the time (days postcoitus) of acute prenatal androgen treatment (APAT). The selected treatment times were 30, 40, 50, and 60 d postcoitus. Acute prenatal androgen treatment involved a single 2-mL i.m. injection of 100 mg/mL testosterone propionate. The statistical analysis of all measured parameters was performed using an analysis of variance via a general linear model. Postnatal plasma testosterone concentrations were not affected by treatment (P > .05). The time of treatment affected the observed responses to APAT (P < .05). Acute prenatal androgen treatment increased birth weight, ADG, and live weight and altered wool growth, plasma insulin levels, and ano-genital distance (P < .05).