Serum testosterone concentration during two breeding cycles of turkeys with low and high ejaculate volumes

Serum testosterone, ejaculate volume, sperm concentration, and total sperm per ejaculate were followed from 24 to 80 weeks of age in Large White breeder turkeys. Blood was collected immediately after the weekly semen collection and serum testosterone was determined by radioimmunoassay. Males were classified as low semen producers (LSP; ejaculate volume <.25 ml) or high semen producers (HSP; ejaculate volume >.50 ml). Semen production, which had started in all males at 28 weeks of age, stopped at 57 ± 2.4 and 62 ± 1.6 weeks, and resumed at 72 ± 0.2 and 71 ± 0.6 weeks (mean ± SEM) for LSP and HSP, respectively. Semen production (volume, concentration, and total sperm) of the second cycle was comparable to that of the first cycle. However, serum testosterone ranged from <.05 ng to 6.0 ng per ml and showed considerable variation within and between males with no significant relationship to either age or ejaculate volume.