Serum testosterone concentrations in alpacas and llamas after human chorionic gonadotropin stimulation before and after castration

Veterinarians perform testosterone stimulation tests in animals suspected of bilateral cryptorchidism and/or incomplete castration. Period for circulating testosterone to become undetectable after castration varies among species. To our knowledge, clearance of circulating testosterone in camelids after castration has not been examined. Testosterone stimulation with human chorionic gonadotropin (hCG) has been described in several species, including alpacas. However, there is limited information regarding responses to hCG in male llamas. Purpose was to measure serum testosterone concentrations [T] in llamas and alpacas after hCG stimulation before and after castration. We hypothesized that [T] significantly increases after hCG treatment and decreases rapidly after castration. Testosterone stimulation test (using hCG) was performed in mature male alpacas (n = 9) and llamas (n = 7) 1 day prior to and 1 day after castration. Blood samples were collected; 1 sample before and 3 samples (2, 4, and 8 hours) after hCG treatment. In llamas and alpacas [T] increased (p < 0.05) > 2 fold (from prehCG values) within 2 hours after hCG treatment. PrehCG [T] were higher (p < 0.05) in alpacas than llamas but did not differ significantly between them after hCG stimulation; 24 hours after castration [T] were < 0.05 ng/ml.