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The interaction of nutrition and body condition at mating on ovulation rate and early embryo mortality in Scottish Blackface ewes

  • R. G. Gunn (a1) and J. M. Doney (a1)
Abstract
SUMMARY

One hundred and fifty-six Scottish Blackface ewes were differentially group-fed over a 2-month period to achieve three distinct levels of body condition (good, moderate and very poor). Over 5 weeks prior to mating, one group of good-condition ewes was maintained in that condition, one group of good- and one of moderate-condition ewes were brought down in condition by restricted feeding and one group of moderate and the very poor condition ewes were raised in condition by a high level of feeding. Ewes were therefore in good, moderately good or poor condition at mating. After mating, ewes were killed either on return to service or at 25 ± 5 days for counts of corpora lutea and viable embryos.

Poor body condition, irrespective of feeding level, was associated with a delay or suppression of oestrus and with a high return-to-service rate. Ovulation rate was positively related to body condition at mating but not to the level of pre-mating food intake at the condition levels studied.

Embryo mortality decreased as body condition at mating increased and the interaction between condition and the level of pre-mating food intake had a differential effect on mortality of single- and multiple-shed ova. The lowest rate of embryo mortality was found in ewes in moderately good condition which had been well-fed before mating.

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A. W. H. Braden (1971). Studies in flock mating of sheep. 3. Effect of undernutrition of ewes during joining. Australian Journal of Experimental Agriculture and Animal Husbandry 11, 375–8.

J. M. Doney , R. G. Gunn & J. G. Griffiths (1973). The effect of premating stress on the onset of oestrus and on ovulation rate in Scottish Blackface ewes. Journal of Reproduction and Fertility 35, 381–4.

J. M. Doney , R. G. Gunn & W. F. Smith (1973). Transuterine migration and embryo survival in sheep. Journal of Reproduction and Fertility 34, 363–7.

I. C. Fletcher (1971). Effects of nutrition, liveweight and season on the incidence of twin ovulation in South Australian strong-wool Merino ewes. Australian Journal of Agricultural Research 22, 321–30.

I. D. Killeen (1974). Effects of live weight of Border Leicester × Merino ewes and breed of ram on fertilization in flock mated sheep. Journal of Reproduction and Fertility 36, 464.

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The Journal of Agricultural Science
  • ISSN: 0021-8596
  • EISSN: 1469-5146
  • URL: /core/journals/journal-of-agricultural-science
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