THE EFFECT OF MATERNAL IMMUNITY ON THE SURVIVAL OF GOATxSHEEP HYBRID EMBRYOS

Abstract

Summary. The survival of goat×sheep hybrid embryos in goats carrying hybrids for the first time was compared to that in goats which had carried hybrids in previous breeding seasons and in goats sensitized against sheep antigens. The findings on the goats carrying hybrids for the first time showed that embryonic death occurred during the 6th week of gestation; twelve live embryos (crown-rump lengths, 22 to 36 mm) were recovered from seven goats examined on Days 35 to 38 of pregnancy, and eight dead embryos (crown-rump lengths, 20 to 38 mm) were recovered from six goats at Days 38 to 43. The size of dead embryos (crown-rump lengths, 7 to 11 mm) recovered from four of five goats carrying hybrids for the second time suggests that survival did not extend much beyond the 3rd week of gestation. Six goats which had received skin grafts and injections of leucocytes from the sheep used for insemination were examined at Days 35 and 36 of pregnancy; live embryos (crown-rump lengths, 25 to 26 mm) were recovered from two goats, and dead embryos (crown-rump lengths, 10 to 16 mm) were recovered from four goats.