Wastage of ova in young Merino ewes.
Eight sub-flocks each of 48 to 51 Merino ewes were mated for 18 days with 1 ram to each subflock. Four of the sub-flocks were of non-parous 1.5-year-old ewes and the other 4 were of parous 2.5-year-old ewes. Fertilisation rates for the subflocks of 1.5-year-old ewes varied from 83 to 94%, and the sub-flocks of 2.5-year-old ewes ranged from 81 to 94%. By day 29 post coitum 42% and 56% of 1.5-year-old ewes in sub-flocks 1 and 2 respectively were no longer pregnant. Embryonic mortality was low in other sub-flocks of 1.5- and 2.5-year-old ewes. Virtually all embryonic death occurred after day 12 post coitum. The sporadic occurrence of high ova wastage in maiden 1.5-year-old ewes in this experiment and in others is discussed in relation to the short duration of oestrus in young ewes and the great variation in service activity of rams.
D000367:Age Factors; D000818:Animals; D003307:Copulation; D020964:Embryo Loss / Q000662:veterinary*; D004971:Estrus; D005260:Female; D005306:Fertilization; D005313:Fetal Death / Q000662:veterinary*; D008297:Male; D010063:Ovum / Q000502:physiology*; D010298:Parity; D011247:Pregnancy; D012756:Sheep / Q000502:physiology*; D012757:Sheep Diseases / Q000453:epidemiology*; D013997:Time Factors