REPRODUCTIVE PERFORMANCE IN EWES ON A LOW-SELENIUM DIET
Sixty-four Selenium (Se)-deficient ewes (group 1) and 65 Se-adequate ewes (group 2) were exposed to fertile, harnessed rams for a 42-day period (1 October–12 November 1973). Between 26 October and 7 December, approximately half of the animals in each group were slaughtered 25–30 days after their last marked mating to determine numbers of embryos and corpora lutea (CL). The percentages of ewes pregnant and CL not represented by normal embryos were 80.6 and 12.8 in group 1 and 78.8 and 34.1 in group 2 and the average number of CL/ewe was 1.57 and 1.63, respectively. The remaining ewes were kept until anticipated time of lambing. The percentage of ewes which lambed and the average number of lambs/ewe were 67.9 and 1.47 (group 1) and 71.9 and 1.44 (group 2). No group differences in sex ratio of lambs was observed. Composite conception rates for the slaughtered and lambed ewes were 76.2% for the Se-deficient and 76.6% for the Se-adequate animals. It was concluded that under the conditions of this experiment Se depletion had no adverse effect on ewe conception rates, embryonic mortality or numbers of lambs born.