| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 2097504 | Theriogenology | 2005 | 8 Pages |
The aim of this study was to investigate the effect of treating anovulatory anestrous (AA) dairy cows with 1500 IU of hCG IM, 5 d after insemination, on their first service conception rate. A clinical trial was conducted during the 2003/2004 breeding season involving 442 AA dairy cows in six herds. On Day −8, all cows were treated with a progesterone-containing intravaginal device (Cue-Mate®). The devices were removed on Day −2, and on Day −1 all cows received an IM injection of 1 mg of estradiol benzoate. Cows in the control group (n = 220) received no further treatments. Cows in the treatment group (n = 222) which had been inseminated on Days 0 or 1 were treated with 1500 IU of hCG IM 5 d after insemination. Blood was collected from 30 cows (15 in each group) on Days 5 and 12 after AI for analysis of plasma P4 concentration. There was no difference in first service conception rates between the control and treatment groups (46.3% versus 43.6%, respectively; P = 0.68), despite the fact that plasma P4 concentrations were higher in the treatment group on Day 12 (4.9 ± 1.3 ng/mL versus 6.2 ± 2.7 ng/mL for control and treatment groups, respectively; P < 0.01). In conclusion, 1500 IU of hCG 5 d after insemination did not improve first service conception rate in AA dairy cows.
