title: Apparent decline in fertility in heifers after repeated oestrus synchronisation with cloprostenol.
abstract: Over several years groups of heifers which were repeatedly treated with the PGF2 alpha analogue, cloprostenol, to synchronise oestrus were artificially inseminated. When sperm treatment was optimised, a reduction in conception rate was observed which was related to the number of synchronisation treatments the animals had received. Although factors such as a seasonal reduction in fertility may have contributed to the effect, there appeared to be a decrease in the proportion of animals becoming pregnant after successive synchronisations. Possible explanations for this observation are suggested.
authors.affiliation: National Institute for Medical Research, Mill Hill, London.
authors.forename: J M
authors.initials: JM
authors.lastname: Morrell
authors.forename: D E
authors.initials: DE
authors.lastname: Noakes
authors.forename: E
authors.initials: E
authors.lastname: Zintzaras
authors.forename: D W
authors.initials: DW
authors.lastname: Dresser
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D003008:Cloprostenol / Q000009:adverse effects*; D004973:Estrus Synchronization; D005260:Female; D005298:Fertility / Q000187:drug effects*; D005306:Fertilization / Q000187:drug effects*; D007315:Insemination, Artificial / Q000662:veterinary; D008297:Male; D011247:Pregnancy; D011336:Probability; D012621:Seasons; D012661:Semen / Q000166:cytology
chemical_list: D003008:Cloprostenol