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The Role of Maternal Effects in Animal Breeding: VII. Maternal Effects in Sheep^{1, 2,}

University of California, Davis 95616

Abstract

THE term maternal effect implies an influence of the mother on her offspring other than through the genes she transmits to it. Variation between females in maternal performance may of course arise from either genetic or environmental causes.

Maternal effects may be expected to be more important in sheep than in cattle or swine because of the greater relative variation in litter size in sheep and the fact that many lambs are partially dependent on their mother's milk supply until the time of marketing, or at least until they have achieved a higher proportion of their slaughter weight than is the case for cattle and swine.

The biometrical aspects of this subject are covered in other papers in this symposium, and the number of studies using this approach with sheep data is very limited. Emphasis in this paper will therefore be on the more physiological aspects, excluding immunological aspects which are also reviewed elsewhere in the symposium. The nature and degree of maternal influence on some parameters of biological and economic interest will be considered, to be followed by a discussion of the implications of this information for sheep breeding.

¹ "Presented at a symposium on The Role of Maternal Effects in Animal Breeding sponsored by the American Society of Animal Science, August 3, 1971, University of California, Davis."

² The author expresses his appreciation to D. T. Torell, J. F. Quirke and R. Hart for permission to quote unpublished data from collaborative research projects. The paper was written during a leave spent at the A.R.C. Animal Breeding Research Organization, Edinburgh, and the support and stimulation provided by Professor H. P. Donald, Director of A.B.R.O., are gratefully acknowledged.