Abstract
A total of 226 first lactating Holstein cows were treated with commercially available porcine FSH (FSH-P) and PGF2α(Tham-salt) or PGF2α, -analogue (cloprostenol) at the mid-functional luteal stage to induce twin pregnancy. The rate of showing estrus was lower in cows treated with PGF2α 1520 mg than PGF2α, -analogue 0.5 mg, and there was not difference between PGF2α, -analogue 0.5 mg and PGF2α 30 mg. The 24-hrs interval between the first FSH-P and PGF2α-analogue injection was slightly more effective than the 48-hrs interval to induce estrus and pregnancy. Total amount of FSH-P was positively correlated with the number of corpora lutea (CL) after estrus, and 1215 AU FSH-P treatment induced higher percentages of cows with 3 CL or over and abortion than those of 6-10 AU FSH-P treatment. No difference was noted in response to a total 6 AU FSH-P treatment between 1 and 2 injections per day through 2 days. The rate of abortion in the pregnant cows with 1, 2 and 3 CL were 1/20, 1/23 and 4/14, respectively. Therefore, it is suggested the appropriate ovulation rate is 2 and that treatment with 46 AU FSH-P on the first day and 24 AU FSH-P plus 0.5 mg PGF2α, -analogue on the second day is the practical schedule of the hormonal treatment.
