title: The effect of GnRH or oestradiol injected at pro-oestrus on luteal function and follicular dynamics of the subsequent oestrous cycle in non-lactating cycling Holstein cows.
abstract: Oestrous synchronization involves synchronization of ovarian follicular turnover, new wave emergence, and finally induction of ovulation. The final step can be synchronized by the parenteral administration of either GnRH or oestradiol benzoate. This study investigated corpus luteum and follicular emergence after ovulation had been induced by the administration of either GnRH or oestradiol benzoate. The injection of oestradiol benzoate may have delayed the emergence of the first follicular wave subsequent to the induced ovulation; administration of oestradiol benzoate or GnRH lowered the progesterone rise so that the maximum dioestrous concentration of progesterone on Day 9 was lower when cows were treated during pro-oestrus compared to the spontaneously ovulating controls. One implication of findings from the present study is that induction of ovulation with either oestradiol benzoate or GnRH, administered 24 or 36 h after withdrawal of the CIDR device, respectively, may lower fertility. Future studies must identify the timing of administration relative to the time of CIDR device withdrawal and the optimum concentration of oestradiol benzoate or GnRH that would not have untoward effects on the development of the corpus lutea, particularly within the first week of dioestrus.
authors.affiliation: Applied Neurobiology Group, Faculty of Veterinary Medicine, University of Glasgow, 464 Bearsden Road, Glasgow, G61 1QH, UK. besegwagwe@yahoo.co.uk
authors.forename: B V E
authors.initials: BV
authors.lastname: Segwagwe
authors.forename: K L
authors.initials: KL
authors.lastname: Macmillan
authors.forename: P D
authors.initials: PD
authors.lastname: Mansell
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D004343:Drug Implants; D004958:Estradiol / Q000494:pharmacology*; D004971:Estrus / Q000187:drug effects / Q000502:physiology; D004973:Estrus Synchronization / Q000187:drug effects / Q000379:methods; D005260:Female; D005300:Fertility Agents, Female / Q000494:pharmacology*; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D008183:Luteal Phase / Q000187:drug effects / Q000502:physiology; D006080:Ovarian Follicle / Q000187:drug effects* / Q000502:physiology; D010060:Ovulation / Q000187:drug effects* / Q000502:physiology; D010062:Ovulation Induction / Q000009:adverse effects / Q000379:methods / Q000662:veterinary*; D011374:Progesterone / Q000008:administration & dosage / Q000097:blood; D011897:Random Allocation; D013997:Time Factors
chemical_list: D004343:Drug Implants; D005300:Fertility Agents, Female; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D004958:Estradiol