Effects of nutrition on seasonal changes in testosterone levels in young male reindeer (Rangifer tarandus tarandus).

Food restriction during autumn in male reindeer calves decreased peak testosterone levels at 4-6 months, and also at 16-17 months of age. Peak testosterone levels at the age of 16-17 months were significantly correlated to body weight at 6 months but not to body weight at 16 months of age. There were small secondary testosterone peaks (1-3 ng/ml) in March or April in 11 of 16 animals. Testosterone levels started to increase before summer solstice in 50% of the yearlings.