Thyroid status and embryonic mortality in swine

¹ Department of Animal Science, State College of Washington, Pullman, Washington

Three lots of 10 Palouse gilts each were used to test the effect of altered thyroid activity on embryonic mortality in swine. Two lots received 0.15% thiouracil and 0.0123% thyroprotein, respectively, in a basal ration; the third lot served as the control. All gilts were assigned to treatment groups at first estrus, bred to fertile boars at third estrus and slaughtered 38 days post coitum. An analysis of variance revealed no statistically significant differences among lots for: ovulation rate, embryonic mortality during the first 38 days of gestation, or number of normal embryos at 38 days post coitum. Crown-rump lengths of normal embryos carried by thyroprotein-treated and control gilts were longer than those of normal embryos carried by thiouracil-treated gilts (P < 0.01). There was a trend toward lowered ovulation rate and reduced embryonic mortality in the gilts receiving thyroprotein. The significance of these results is discussed in relation to BMR and pregnancy in women.