SEASONAL LEVELS OF REPRODUCTIVE HORMONES AND THEIR RELATIONSHIP TO THE ANTLER CYCLE OF MALE AND FEMALE REINDEER (RANGIFER TARANDUS)

Seasonal levels of LH, FSH, testosterone (T), estradiol, progesterone (P), and prolactin (PRL) were determined in the plasma of five adult b ulls, and five barren and four pregnant cows of Alaskan reindeer (Rang ifer tarandus), which were sampled every 3 weeks for 54 weeks. The mal e reproductive axis was sequentially activated; LH peaked in May-June (2 ng/ml), FSH in June (51 ng/ml), and T in September (11.8 ng/ml). LH levels in females reached a maximum in both groups at the end of Augu st (the beginning of the rut). Seasonal variation in FSH was minimal i n pregnant cows, but exhibited one elevation (41 ng/ml) in barren ones in November. T levels in cows remained at barely detectable levels. T he decrease of T values observed in both groups in December and March was not significant. PRL peaked in May in cows (135 ng/ml pregnant, 14 0 ng/ml non-pregnant) and in June in bulls (92 ng/ml). Estradiol was h ighest in bulls in the rut (August), in non-pregnant cows in January a nd in pregnant cows in April, shortly before parturition. P levels in the pregnant cows rose from September and peaked (9 ng/ml) shortly bef ore parturition in April. In the non-pregnant females P values increas ed and decreased several times before peaking (5 ng/ml) in March. In t he males, the variation of T and estradiol levels correlated relativel y well with the antler cycle but in the females the variation of neith er estradiol, progesterone nor T appeared to be related to mineralizat ion or casting of antlers. Copyright (C) 1997 Elsevier Science Inc.