title: The effect of hCG administration five days after insemination on the first service conception rate of anestrous dairy cows.
abstract: 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 1mg 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.
authors.affiliation: Matamata Veterinary Services Ltd., 26 Tainui St., Matamata, New Zealand. daveh@matavet.co.nz
authors.forename: D W
authors.initials: DW
authors.lastname: Hanlon
authors.forename: G M
authors.initials: GM
authors.lastname: Jarratt
authors.forename: P J
authors.initials: PJ
authors.lastname: Davidson
authors.forename: A J
authors.initials: AJ
authors.lastname: Millar
authors.forename: V L
authors.initials: VL
authors.lastname: Douglas
mesh_terms: D000780:Anestrus / Q000502:physiology; D000818:Animals; D002417:Cattle / Q000502:physiology*; D006063:Chorionic Gonadotropin / Q000008:administration & dosage*; D004334:Drug Administration Schedule; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D005260:Female; D005306:Fertilization / Q000187:drug effects / Q000502:physiology; D007315:Insemination, Artificial / Q000662:veterinary*; D016015:Logistic Models; D008297:Male; D011247:Pregnancy; D011374:Progesterone / Q000097:blood / Q000494:pharmacology*
chemical_list: D006063:Chorionic Gonadotropin; C074283:estradiol 3-benzoate; D011374:Progesterone; D004958:Estradiol