Abstract

Marked genetic differences in ovulation rate provide a potentially powerful tool to elucidate the mechanisms which control ovulation rate. Many breeds of sheep have high ovulation rates and these can be divided into two groups. The first group includes the Romanov, Finnish Landrace and D’Man breeds, in which high ovulation rate reflects polygenic differences for genes with small effects. The second group reflects the action of a single gene, or a closely linked group of genes, such as the Booroola (Fee*) Merino, Icelandic, Javanese Fat-Tail, Inverdale (FecX ) Romney, Belclare, Cambridge and Olkuska. This paper reviews results from studies on gonadotrophin secretion, follicular growth and aspects of ovarian function in relation to genetic differences in ovulation rate in order to determine the likely underlying mechanisms. Are these operating primarily at the ovarian level or are the differences in ovarian function caused by differences at the level of the hypothalamus/pituitary gland?

R. Webb, M. A Driancourt, J. P Hanrahan

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 27: Reproduction; fish breeding; genetics and the environment; genetics in agricultural systems; disease resistance; animal welf, , 3–10, 1998
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