Post-breeding Treatments to lmprove Fertility in Lactating Dairy Cows

Abstract

Lactating Holstein cows were assigned randomly to treatments to improve fertility after first postpartum timed artificial insemination (TAI). In Experiment 1, cows received no treatment (C; n = 223); a CIDR insert from five to 12 days after TAI (CIDR; n = 218); or 100 μg of genadotropin releasing hormone (GnRH) five days after TAI (G5; n = 227). In Experiment 2, cows received C (n = 160), G5 (n = 159), or treatment with 100 μg of GnRH seven days after TAI (G7; n = 163). Although treatment did not affect fertility, when data were combined to compare C (n = 383) and G5 (n = 386) treatments, pregnancies per AI (P/AI) tended to be greater for G5 (49.1 %) than C (45.8 %) cows, and this effect resulted from a GnRH treatment by cyclicity status interaction in which P/AI for anovular cows receiving G5 was greater than that for anovular C cows (45.5 vs. 31.1%). In conclusion, treatment with CIDR inserts after TAI had no effect on fertility, whereas treatment with GnRH five days after TAI improved fertility for anovular, but not for cycling cows.