Seasonal variations in superovulatory responses of Holstein cows treated with pregnant mare serum gonadotrophin under semi-arid environment

This study was designed to examine the effect of hot summer season on superovulatory responses of 20 Holstein cows in a semi-arid environment. Oestrus was synchronised using two injections of 15 mg prostaglandin F2α(PG; Prosolvin, Intervet, Holland) given 11 days apart. In each season, ten cows were superovulated with 2000 iu (International Units) of intramuscular pregnant mare serum gonadotrophin (PMSG) on day 10 of their synchronised oestrous cycle. All cows were treated with PG on day 12 of oestrous cycle and naturally mated during oestrus. Embryos were collected nonsurgically on day 6 post mating. On the day of embryo recovery, the number of corpora lutea (CL) were counted by rectal palpation. Daily blood samples were collected during the study period. The results showed that ovarian responses were adversely affected by the hot summer as indicated by a reduced number of CL, total ova/embryos and quality of embryos during summer compared to winter. Although summer heat did not significantly affect progesterone (P4) and oestradiol (OE2) concentrations, P4levels tended to be higher in winter compared to summer. It is concluded that the superovulatory responses in cows in a semi-arid climate were adversely affected by hot summer months compared to winter.