Effects of changing daylength pattern around the mating period on the mating and lambing performance of Border Leicester-Merino cross ewes

Abstract

In three experiments over two years at Kybybolite, South Australia, Border Leicester x Merino ewes were subjected to treatments in which the effects of natural daylength (C) around mating in midsummer were compared with decreasing long daylength (DL), decreasing short daylength (DS) or a constant daylength of ten hours for 6, 3 or 1 week (Const, 6, Const. 3 and Const. 1) before mating. The DS treatment increased the number of lambs born per ewe from 1.34 to 1.56 and from 1.38 to 1.80 in two experiments with aged ewes. This increase was due to a rise in the proportion of multiple births from 37 out of 92 to 62 out of 94, and from 25 out of 49 births to 43 out of 52, respectively. The most effective treatment for 1 1/2-year-old maiden ewes was Const. 3. This treatment increased the proportion of multiple births from 19 out of 52 births to 38 out of 58, and decreased the number of ewes not lambing from 8 out of 60 to 2 out of 60. Two other short daylength treatments significantly decreased the number of ewes not lambing. Treatments were designed so that they could be readily adapted to commercial practice.