The effect of hCG administration five days after insemination on the first service conception rate of anestrous dairy cows

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 (R)). 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 rated in AA dairy. cows. (c) 2004 Elsevier Inc. All rights reserved.