Sexual/Endocrine Parameters in Peul and Tuareg Rams: Genetic Type and Seasonal Influence

Abstract

Endocrinal parameters of two sexual hormones [luteinizing hormone (LH) and testosterone] were studied in three Tuareg rams and two bicolor Peul rams during April and October 1997. Blood samples were collected at 15 min intervals from 1h00 to 7h00 AM. Means (± standard error) obtained for the various parameters studied in Peul and Tuareg rams were as follows, respectively: basal levels of testosterone 4.17 ± 1.82 and 4.55 ± 2.71 ng/ml, and LH 0.80 ± 0.13 and 0.96 ± 0.33 ng/ml; peaks of testosterone 10.16 ± 3.11 and 11.09 ± 2.82 ng/ml, and LH 1.75 ± 0.90 and 2.65 ± 1.29 ng/ml; duration of peaks of testosterone 85 ± 18.7 and 88.63 ± 27.47 min, and LH 75 ± 23.71 and 61.87 ± 24.23 min; frequency of peaks of testosterone 2.38 ± 1.3 and 2.03 ± 1.2 peaks/6h, and LH 1.08 ± 0.15 and 1.85 ± 0.97 peaks/6h. Time intervals between the peak of LH and the first significant rise of testosterone were 26.25 ± 6.49 and 31.87 ± 15.79 min, respectively. The only significant (p < 0.05) differences between the two breeds were their average amplitude of LH. Tuareg rams had an amplitude higher than that of Peuls (2.65 ± 1.29 ng/ml vs 1.75 ± 0.90 ng/ml). For all the other parameters studied, the differences between the two breeds were not significant (p > 0.05). The duration of the peak of LH was significantly affected by the season (p < 0.05), whereas the other parameters were not. Parallel evolutions of the basal levels of testosterone and LH during both seasons highlighted the interaction between the two hormones.