Resumen

MENDEZ VILLALOBOS, Guadalupe et al. Reproductive function in rams imported from New Zealand during their first reproductive season in Mexico. Vet. Méx [online]. 2009, vol.40, n.2, pp.123-131. ISSN 0301-5092.

Importation of rams of high genetic value is a common practice in Mexico; nevertheless, reproductive variables of imported animals have not been followed along. The objective of this study was to evaluate the reproductive function of Suffolk rams along their first reproductive season in Mexico (October to February). The behavior of values of scrotal circumference, sperm count and morphology, and circulating testosterone in Suffolk ram during its first reproductive season in Mexico are in line with the ones reported for Suffolk rams in other latitudes; however, in Mexico such changes are lower in magnitude. Neuroendocrine-reproductive changes induced by environmental stimuli such as changes in duration of light-dark cycles have been broadly documented and are accepted as inducers of seasonal changes in the ram's behavior. In this work, both testosterone concentration and sperm production were observed in December. These results show that Suffolk ram imported to Mexico maintain their cyclic testicular function, although it has a lower magnitude than in other latitudes. Causes of this condition are unknown, but they may be related to changes in the duration of the light-dark cycles prevailing in Mexico.

Palabras llave : reproductive function; sperm; sexual steroid hormones; progesterone; testosterone; estradiol; Suffolk rams.