Early Pregnancy Loss in Sheep at Ambient Temperatures of 70° and 90° F. as Determined by Embryo Transfer

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Abstract
Early embryo development in ewes maintained in ambient temperatures of 70° F. or 90° F. was studied by means of embryo transfers. Transfers were performed approximately 72 hours after onset of estrus and successful transfers were verified by a laporatomy performed 25–30 days later. Where both donor and recipient were maintained at 70° F., 13 of 23 (56.5%) “between animal” transfers were successful as compared with 2 of 21 (9.5%) where donor and recipient were maintained at 90° F. and 70° F. respectively. Therefore, some detrimental action had occurred by 3 days after onset of estrus in ewes at 90dg F. Although morphological differences were not apparent at the time of transfer, embryonic death occurred at a later stage of development in uteri known to be capable of supporting embryonic growth. Where embryos were transferred from donor to recipient ewes maintained at 70° F. and 90° F. respectively, 6 of 25 (24.0%) transfers were successful. To evaluate possible harmful effects of transfer, embryos were either not transferred or were replaced in the original donor when multiple ovulations occurred. Five of seven (71.4%) and none of four non-transferred embryos continued development in 70° F. and 90° F. groups respectively, assuming one embryo was produced per corpus luteum. Six of eight (75.0%) “within animal” transfers were successful in the 70° F. group but no pregnancies resulted from two such transfers in the 90° F. group.