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Melatonin Treatment of Donor and Recipient Ewes in an Embryo Transfer Programme: Effects on Ovulation Rate and Embryo Survival During Normal Seasonal Anoestrus

Published online by Cambridge University Press:  21 November 2017

J.J. Robinson ,
T.G. McEvoy ,
R.P. Aitken  and
I. Robertson
J.J. Robinson
Affiliation:
Rowett Research Institute, Bucksburn, Aberdeen AB2 9SB
T.G. McEvoy
Affiliation:
Rowett Research Institute, Bucksburn, Aberdeen AB2 9SB
R.P. Aitken
Affiliation:
Rowett Research Institute, Bucksburn, Aberdeen AB2 9SB
I. Robertson
Affiliation:
Rowett Research Institute, Bucksburn, Aberdeen AB2 9SB
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Extract

Conception rates and litter sizes in ewes are often higher during the peak of the breeding season than at the beginning or end. How much of this is due to seasonal differences in ovulation rate (Montgomery et al 1988) and ram fertility (Colas, 1983) is uncertain. Using laparoscopic intrauterine insemination which virtually eliminates fertilization failure, Aitken et al (1990) obtained estimates of embryo survival for Greyface ewes induced to ovulate in mid-June (mid anoestrus) that were 25, 19 and 13% below the expected values for 2, 3 and 4 ovulations respectively. While this implies that embryos transferred to recipient ewes at an induced oestrus during seasonal anoestrus may have sub-optimal survival rates, it does not identify whether the cause lies solely with the embryo or with the uterine environment or with both. The present study employs reciprocal embryo transfer in conjunction with melatonin treatment to identify the influence of seasonality on the inherent viability of the embryos and the ability of the uterine environment to sustain pregnancy.

Type
Sheep Production
Information
Proceedings of the British Society of Animal Production (1972) , Volume 1994 , March 1994 , pp. 78
Copyright
Copyright © The British Society of Animal Production 1994

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References

Aitken, R.P., Wallace, J.M. and Robinson, J.J. (1990) Animal Production 50, 379–382.Google Scholar
Colas, G. (1983) In: Sheep Production (Ed., Haresign, W.), Butterworths, London, pp.453–465.Google Scholar
McKelvey, W.A.C., Robinson, J.J., Aitken, R.P. and Robertson, I. (1986) Theriogenology 25, 855–865.CrossRefGoogle Scholar
Montgomery, G.W., Scott, I.C. and Johnstone, P.D. (1988) Animal Reproduction Science 17, 197–205.CrossRefGoogle Scholar