Variation in ovarian activity of Romney Marsh ewes

M.F. McDonald and T.S. Change

Massey University, Palmerston North

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Proceedings of the New Zealand Society of Animal Production. 1966, 26: 98-106

Ovulatory activity (number of corpora lutea) was examined in Romney Marsh ewes at laparotomy after the first and second oestrous periods of the breeding season, Ewes were mated to entire rams at third oestrus and slaughtered nineteen days later.

Following laparotomy, oestrous cycles were normal in length, few ewes showed silent oestrus, and a good conception rate resulted to mating at third oestrus.

Ewes of similar genetic origin, although bred at two farms for five years, when brought into a common environment showed marked differences in ovulatory activity several months later. Irrespective of the farm of origin, twin-born ewes shed more ova than single-born ewes and there was an increase in ovulation rate with advancement in order of oestrus.

Use of the cumulative number of corpora lutea formed over several oestrous periods, as a criterion of reproductive function, is discussed.

Keywords: NZSAPAB;

Last Updated 24-08-2000