Ovulation and embryo survival rates and plasma progesterone concentrations of prolific ewes treated with PMSG.
Finnish Landrace x Dorset Horn ewes of two flocks comprising 47 and 51 animals were mated to Suffolk rams at a synchronized oestrus on 9 December (Flock D) and 8 April (Flock A) after treatment with 500 i.u. PMSG. The ewes were slaughtered between 50 and 145 days of pregnancy. The mean +/- s.e.m. ovulation rates were 4.5 +/- 0.24 (Flock D) and 5.0 +/- 0.32 (Flock A) for ewes which conceived to the induced oestrus and the corresponding litter sizes were 2.8 +/- 0.15 and 2.8 +/- 0.18. Mean concentrations of progesterone in the peripheral plasma during pregnancy were higher for Flock D than for Flock A ewes both in early (P less than 0.001) and late (P less than 0.05) pregnancy. An increase in ovulation rate, up to 4 or 5, was associated with an increase in mean litter size. There was evidence that higher ovulation rates were counterproductive.
D000818:Animals; D004622:Embryo, Mammalian / Q000502:physiology*; D004780:Environment, Controlled; D005260:Female; D005313:Fetal Death / Q000453:epidemiology / Q000662:veterinary; D006064:Gonadotropins, Equine / Q000494:pharmacology*; D008098:Litter Size / Q000187:drug effects; D010060:Ovulation / Q000187:drug effects*; D011247:Pregnancy; D011374:Progesterone / Q000097:blood*; D012756:Sheep / Q000502:physiology*; D012757:Sheep Diseases / Q000453:epidemiology
D006064:Gonadotropins, Equine; D011374:Progesterone