title: Effects of progesterone inclusion in a gonadotropin-prostaglandin-gonadotropin programme on follicular dynamics and ovulation synchronisation of pasture-based dairy cows with anoestrous.
abstract: The aim of this study was to evaluate how the addition of a progesterone device to a gonadotropin-prostaglandin-gonadotropin (GPG) programme in dairy cows with postpartum anovulatory anoestrus affected ovarian follicular dynamics and the synchronisation of ovulation. Twenty-two dairy cows were randomly assigned to either GPG (Day 0: 100 μg GnRH, Day 7: 500 μg PGF2α, Day 9: 100 μg GnRH, Day 0-7: Day 10) or GPG with a progesterone device from Day 0 to 7 (GPG+P4). Ovarian follicular dynamics and ovulation synchronisation were studied using transrectal ultrasonography. Compared to the GPG+P4, GPG alone resulted in a relatively larger mean dominant follicle size and a higher mean peripheral oestradiol concentration (74.9 pg ∗ day vs. 60.6 pg ∗ day; P=0.002); however, there was much greater variation in follicle diameter in the group treated with GPG (7.8-22 mm vs. 10.8-17.5mm in GPG+P4) and this may, at least partly explain why only 7/11 cows in this group ovulated within 48 h of the Day 9 GnRH injection compared to 10/10 of the cows in the GPG+P4 group. These results suggest that differences in follicular dynamics between GPG and GPG+P4 programmes are not a key driver of the difference in conception rate, but further studies are required to better assess the role of ovulation synchronisation.
authors.affiliation: Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand. Electronic address: s.k.sahu@massey.ac.nz.
authors.forename: S K
authors.initials: SK
authors.lastname: Sahu
authors.affiliation: Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand.
authors.forename: J F
authors.initials: JF
authors.lastname: Cockrem
authors.affiliation: Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand.
authors.forename: T J
authors.initials: TJ
authors.lastname: Parkinson
authors.affiliation: Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand.
authors.forename: R A
authors.initials: RA
authors.lastname: Laven
mesh_terms: D000780:Anestrus / Q000187:drug effects*; D000818:Animals; D002417:Cattle / Q000502:physiology*; D015237:Dinoprost / Q000494:pharmacology; D004973:Estrus Synchronization / Q000187:drug effects*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D006080:Ovarian Follicle / Q000187:drug effects / Q000502:physiology*; D010060:Ovulation / Q000187:drug effects*; D049590:Postpartum Period; D011374:Progesterone / Q000008:administration & dosage / Q000494:pharmacology*; D011897:Random Allocation
chemical_list: D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D015237:Dinoprost
keywords: Anovulatory anoestrus; GPG; Ovulation; Progesterone; Synchronisation