ORIGINAL A RTICLE Effects of summer heat stress on physiological variables, ovulation and progesterone secretion in Pelibuey ewes under natural outdoor conditions in an arid region

ABSTRACT Ten non-lactating multiparous Pelibuey breed ewes were housed in a corral to evaluate the effects of summer thermal stresson physiologic variables, estrous behavior, ovulation and corpus luteum functionality under natural conditions of an arid re-gion. In summer and autumn, daily estrous detection with a ram fitted with an apron and blood sample collections were per-formed during two natural estrous cycles. An environment of heat stress was detected in summer and thermoneutral inautumn. Rectal temperature and respiratory frequency were greater (P 0.05) live weight, body condition, length of estrous cycle or percentage of ewesin estrous and ovulating. Compared with autumn, serum progesterone concentrations in summer decreased (P<0.05) be-tween days 8 and 14 of the estrous cycle. It is concluded that under outdoor conditions of arid regions, while estrous andovulatory activities of Pelibuey ewes were not affected by summer thermal stress, the corpus luteum functionality wasdecreased.