Rank-dependent plasma levels of LH, FSH and testosterone in male pudu (Pudu puda) after GnRH administration

Pudu (Pudu puda) is the smallest deer of the world. It exhibits a unique se asonal cycle of reproduction, characterized by the biannual peaks of LH and testosterone. In order to elucidate the regulation of reproduction in pudu , plasma concentrations of LH, FSH and testosterone were measured in 3 pair s of adult males (dominant and subordinate), sampled before and after intra muscular administration of GnRH (50 mu g/deer) given at the end of January, one month before the onset of the rut. The hormonal response to GnRH, stud ied in three pairs of bucks (each pair sharing one pen) was evaluated accor ding to dominance relationship. Unlike the subordinate bucks, the dominant animals responded to pretreatment procedures with rising levels of all thre e hormones. In all deer, GnRH administration substantially increased LH and testosterone levels, whereas FSH levels did not change significantly. The elevation in testosterone levels after GnRH was significantly higher in dom inant bucks, as compared to subordinate ones. Conversely, an opposite trend , higher LH values were detected in the subordinate deer. The variation of FSH levels after GnRH did not differ between both groups. The data from pud u were compared to GnRH stimulation tests performed in other cervids.