Abstract
Effectiveness of an intrauterine injection of prostaglandin F2α (PGF2α) on the estrous synchronization in the grazing cow and the fertility at the synchronized estrus were investi-gated.
A total of 52 cows (Holstein 49 and Japanese Black Cattle 3) were treated with 4 or 6 mg of PGF2α during the luteal stage (early 1. s. 7, functional 1. s. 41 and late 1. s. 4) Each doseof PGF2α dissolved in 0.75 ml of aq. distillata was injected singly into the middle portion of an ipsilateral uterine horn to the corpus luteum through the cervix using the metal catheter. Estrus occurred in 12 (23.1%), 28 (53.9%) and 5 (9.6%) cows on 2, 3 and 4 days after the treat-ment respectively, and the remaining 7 cows (13.4%) between 9 and 16 days. It was noticeable that 14 cows which were considered to be silent or dull estrus during the period prior to the treatment revealed distinct estrous signs except 2 cows which showed weak heat. Out of 45 cows which came into estrus during 24 days after the treatment, 37 cows were inseminated with the frozen semen at that time and conceived in 27 cows (73.0%). Two cows were not served due to the weak heat or discharge of unclean mucus and 6 cows due to owner's wish.
These results indicate that an intrauterine injection of PGF2α is an excellent method for the technique of the estrous synchronization in the cow.
