Reproductive behaviour of Saint Croix and Suffolk rams at medium latitudes (19º N) during long days while being exposed to Suffolk ewes in seasonal anestrus

Abstract

Sexual behaviour decreases in sheep breeds of temperate origin during long day length, while tropical rams have been reported to be almost aseasonal. However, changes in sexual behaviour have not been compared between these two breeds, and besides day length no further analysis has been made for other environmental factors. The purpose of this preliminary study was to evaluate the sexual behaviour of Saint Croix and Suffolk rams at medium latitudes (19º N) during long day length, while being exposed to Suffolk ewes in seasonal anestrus, to avoid sexual feedback from the females. In the first group (T1), three Suffolk males were exposed continuously to females during 13 days, while in the second group (T2) three Saint Croix rams were used. Saint Croix rams displayed more (P < 0.05) vocalizations and sniffs than Suffolks (60.6 ± 12.4 vs. 26.8 ± 5.4 and 141.9 ± 17.1 vs. 62.5 ± 11.2, frequencies/h, respectively). Sexual behaviour decreased (P < 0.01) in Suffolk males as the experiment progressed (y = –1.72x + 42.76; P < 0.05) suggesting habituation to the females. In addition, sexual activity also decreased during noon hours in a pattern that was highly correlated (r = –0,8; P < 0.05) with sunlight, while Saint Croix rams maintained a more constant pattern of sexual activity among and within days. It is concluded that at medium latitudes (19º N), sexual behaviour in Suffolk compared to Saint Croix rams during long days decreases as a consequence of the solar radiation and habituation to the anestrous ewes.