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Photoperiodic control of breeding activity in the Southdown ewe with particular reference to the effects of an equatorial light regime

Published online by Cambridge University Press:  27 March 2009

C. J. Thwaites
C. J. Thwaites
Affiliation:
John Hammond Climate Laboratory, Department of Livestock Husbandry, University of New England, Armidale, N.S.W., Australia
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Extract

1. Oestrous activity was studied in three groups of eight Southdown ewes exposed respectively to natural lighting (30½° S.), accentuated reversed seasonal lighting, and equatorial lighting for a period of 2 years.

2. Control ewes exhibited a restricted breeding season confined to the autumn and winter months of each year. The breeding season averaged 102–5 days in length and during it the ewes experienced an average of 7·14 ± 0·47 oestrous periods.

3. The natural breeding season was almost completely reversed by artificial reversal of the normal seasonal variation in daylength. This constitutes presumptive evidence that daylength is the major factor controlling seasonality of oestrus in Southdown ewes.

Type
Research Article
Information
The Journal of Agricultural Science , Volume 65 , Issue 1 , August 1965 , pp. 57 - 64
Copyright
Copyright © Cambridge University Press 1965

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