Sexual Season of the Ewe and Daylight Environment

Abstract

AN exact knowledge of the duration of the breeding season of improved breeds of sheep in relation to daylight changes has an important bearing on the export of such breeds overseas, determining the areas in which different breeds can be used. Transferring sheep from one latitude to another even within the same hemisphere has been shown to have an effect on the ovarian rhythm through the change of light environment^1,2. J. Hammond, jun.³, states that the breeding season of Suffolks is evenly spaced around the shortest day over a period when the length of daylight is 11½ hours or less. J. Hammond, sen.⁴, relates breed differences in the duration of the breeding season to the geographical origin of breed. Yeates⁵ reports that the onset and end of the breeding season occurs 10–14 weeks after the seasonal daylight curve changes over to shorter or longer daylight hours, respectively.