Journal of Fisheries & Livestock Production
Open Access

Abstract

Thermal stress affects the fertility of high producing dairy cattle, badly. This study was conducted to compare Holstein Frisian (HF), cross-bred and indigenous dairy cattle (Sahiwal and Achai) in terms of effects of ambient temperature on HSP-70 expression, serum P4, glucose and cortisol concentrations and follicular number during the dioestrus period of the estrous cycle. Thirty six multiparous lactating dairy cows with normal cyclicity comprising nine cows from each breed of Sahiwal, Achai, crossbred and HF were selected in two state farms in Peshawar located at 34.0�°N, 71.6�°E. Blood sampling was conducted at an average ambient temperature of 18�°C (thermoneutral) in February, 32�°C (thermal transitional) in April and 42�°C (thermal stress) in late June. Rectal ovarian ultrasonography was performed to determine follicular dynamics. Thermal stress increased concentrations of glucose (P<0.05), cortisol (P<0.001), HSP-70 (P<0.001) and number of follicles (P<0.01), while decreased progesterone (P<0.01) in all four breeds beyond 32�°C; however, Achai cows resisted elevation of HSP-70 levels with the increasing ambient temperature up to 32�°C. As the ambient temperature increased to 32�°C and 42 �°C, a notable elevation was observed in the first four parameters while progesterone concentrations were decreased. Positive correlation was found between level of glucose, cortisol and HSP-70 with the rise in ambient temperature while progesterone concentrations related negatively with the changing temperature. The number of follicles related positively with ambient temperature, cortisol, HSP-70 and blood glucose and negatively with progesterone concentrations. It is concluded that thermal stress elevated concentration of HSP-70 associated with enhanced concentration of glucose, cortisol and number of follicles. Progesterone concentration provided a good indication of fertility and related negatively with the thermal stress; however, the number of follicles may be considered as a negative indicator of fertility due to lack of a dominant follicle. The indigenous dairy breeds resisted heat stress better than the exotic and crossbred cows indicating that the later are more susceptible to heat stress than the former breeds.

Biography

Email: drmsqureshi@aup.edu.pk