Nutritional stress and pre-implantation embryonic mortality in Merino sheep, 1966

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Abstract
SUMMARY Mature Merino ewes (108) which had been hand-mated to fertile rams received the following treatments: 1, submaintenance nutrition days 7–14 (34 ewes); 2, submaintenance nutrition days 20–27 (40 ewes); 3, control (34 ewes). The ewes were in fat condition, and gained weight before mating and throughout pregnancy except when on the submaintenance treatment. Their overall ovulation rate was 180·6%. The percentages of ova not represented by lambs at term were 30·6, 37·5 and 41·0 for groups 1–3 respectively, the differences being non-significant. Loss of ova in multiple ovulators was not significantly different from that in single ovulators and there was no relationship between body weight and prenatal loss. Nine post-mating oestrous cycles longer than 21 days were distributed through all groups in a pattern which bore no apparent relationship to nutritionally-induced embryo mortality. A higher proportion of ewes remained barren when re-mated after long than after normal-length oestrous cycles.

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