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 Actividad reproductiva de carneros Santa Cruz y Suffolk en latitudes medias (19o N) durante días largos mientras son expuestas ante hembras Suffolk en anestro estacional

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. En las razas de origen templado, la conducta sexual disminuye durante los días largos, mientras que en los carneros tropicales se observa poco este efecto. Sin embargo, los cambios en la conducta sexual entre estas dos razas no se han comparado, y tampoco se han considerado para su análisis otros factores ambientales que pudieran estar involucrados, diferentes a la longitud del día. El propósito de este estudio preliminar fue el de evaluar la conducta sexual de carneros Santa Cruz y Suffolk a latitudes medias (19o N), durante días largos, durante su exposición a borregas Suffolk en anestro estacional, con el fin de evitar la retroalimentación sexual de las hembras. En el primer grupo (T1), tres machos Suffolk se expusieron de manera continua por 13 días a las hembras, mientras que en el segundo grupo (T2) se utilizaron tres machos Santa Cruz. Los machos Santa Cruz realizaron más (P < 0,05) vocalizaciones y olfateos que los Suffolks (60,6 ± 12.4 vs. 26,8 ± 5,4 y 141,9 ± 17,1 vs. 62,5 ± 11,2, frecuencias/h, respectivamente). La actividad sexual disminuyó (P