Transuterine Migration and Embryo Survival in Sheep

The frequency with which transuterine migration of embryos occurs in sheep has been studied by a number of workers (Casida, Woody & Pope, 1966; Baier & Russe, 1968; Scanlon, 1972). When a single ovum is shed from one or both ovaries, the resultant embryo tends to be located in the associated horn of the uterus. When two or more ova are shed from a single ovary, migration of one embryo to the contralateral horn is the general rule, even when this uterine horn is not associated with a CL. There appears to be a greater loss of embryos in ewes with two CL in one ovary than in ewes with a single CL in each ovary, and although it has been suggested that migration is responsible for higher mortality, Sittmann (1972) considered that the available evidence did not support it. From studies on egg transfer in cattle, Rowson, Lawson &