Optimizing estrous period characteristics of crossbred cows exhibiting prolonged estrus using a PGF2α analogue

The present study aimed at optimization of estrous period of prolonged estrus exhibiting crossbred cows (n=10) using PGF 2α analogue (cloprostenol 500µg, i/m) administration between days 7 to 9 post-ovulation. Using a scoring chart, cows were scheduled for visual estrus detection, twice per day for 30 min. After each schedule, ultrasonography was done to detect the ovulation time. A scoring scale was used for the recording of visual estrus signs and estrus related alterations in the genital tract. During spontaneous-estrus (124.5±24h), ovulatory follicles had continuous growth before ovulation. During induced-estrus (32±3.5h), the maximum diameter of ovulatory follicle was similar to spontaneousestrus. The corpus luteum (CL) exhibited slow regression during spontaneous-estrus. The inconsistent estrous score recorded during the extended estrous period was normalized at induced-estrus. In summary, the slow ovulatory follicle growth and CL regression could be associated with the persistence of estrous characteristics, which were optimized following PGF 2α administration during early-luteal phase of cows.