Comparison of synchronization of ovulation and induction of estrus as therapeutic strategies for bovine ovarian cysts in the dairy cow

The benefit of using timed-insemination in lactating dairy cows for the tre atment of ovarian cysts lies in the fact that cows do not have to be detect ed in estrus for insemination and achieving pregnancy. We compared the effe ctiveness of synchronization of ovulation with timed-insemination and induc tion of estrus with insemination at estrus in the treatment of bovine ovari an cysts in lactating dairy cows. After Day 65 post partum, a total of 368 lactating dairy cows was divided into 3 groups. Cows in Group 1 (n= 209, no rmal, noncystic) were treated with 100 ug, im GnRH on Day 0; 25 mg, im PGF( 2 alpha) on Day 7; and 100 ug, im GnRH on Day 9 and then were time-insemina ted 16 h later. Cows in Group 2 (n=76, abnormal, cystic) were treated with 100 ug, im GnRH on Day 0; 25 mg, im PGF(2 alpha) on Day 7; and 100 ug, im G nRH on Day 9 and time-inseminated 16 h later. Cows in Group 3 (n=83, abnorm al, cystic)were treated with 100 ug, im GnRH on Day 0; 25 mg, im PGF(2 alph a) on Day 7; and inseminated at induced estrus within 7 d after treatment w ith PGF(2 alpha). Day 0 was the day of initiation of the study. Conception and pregnancy rates among groups were compared using logistic regression an d adjusted for parity, time of year and days in milk. Conception and pregna ncy rates of Group 1 cows (31.5%) were not significantly different from tho se of Group 2 cows (23.6%). However, the pregnancy rate in normal cows (Gro up 1) was higher (P<0.01) than in cystic cows (Groups 2 and 3). Cows in Gro up 3 had a higher conception rate than cows in Group 2 (51.7%>23.6%; P<0.01 ). However, pregnancy rates for cows in Groups 2 (23.6%) and 3 (18%) were n ot significantly different. The finding indicated that synchronization of o vulation and timed-insemination resulted in pregnancy rates similar to thos e of synchronization of estrus and insemination at an induced estrus within 7 d for the treatment of ovarian cysts in lactating dairy cows. (C) 2000 b y Elsevier Science Inc.