Effects of season on the secretion of LH and testosterone in intact and castrated red deer stags (Cervus elaphus)

At 2--4 monthly intervals during the year blood samples were collected every 15 min for 6 h from 2 intact and 3 castrated red deer stags to study the relationship between season and the secretion of LH and testosterone. In the intact stags plasma LH and testosterone concentrations changed during the year; the LH levels were maximal in August during the phase of testicular redevelopment, while the testosterone levels were maximal from September to November coinciding with the time of peak testicular activity and the mating season. The castrated stags had higher plasma levels of LH than the intact stags at all times of the year, and there was no clear seasonal cycle in LH levels in these animals.