Embryonic mortality and uterine infection in the pig

Summary. Thirty-nine gilts were slaughtered 9 and 13 days post coitum(p.c.) to determine if the period of elongation and first attachment of the blastocyst to the uterus was critical in embryonic survival. The bacterial flora of the uteri of thirty-eight pigs were cultured to determine the relationship between bacterial infection and embryonic mortality at these times. The embryonic loss in fifteen pregnant pigs killed 13 days p.c. was significantly greater than that in fifteen pregnant pigs killed 9 days p.c. Six pigs slaughtered 13 days p.c. and three 9 days p.c. were not pregnant. No abnormal embryos were found in the 9-day group but in nine pigs in the 13-day group, embryos or embryonic membranes tangled in mucus were recovered from the cervical end of the uterine horns. Most of the embryonic discs appeared normal but there was evidence that degeneration of embryos and their membranes occurred within the mucus. Leucocytic invasion of the mass appeared to be associated with advanced degeneration. Uterine bacterial flora were compatible with pregnancy. There was, however, a significant difference in the embryonic loss between pigs with sterile and infected uteri at both 9 and 13 days p.c., the difference being greater in the 13-day group. The findings suggest that infection of the uterus may be a major factor in the loss of embryos during early pregnancy and may result in a large proportion of infected pigs returning to service