Effects of steroids, bluetongue virus, and Brucella Abortus on ova fertilization and embryo mortality in superovulated cows

Abstract

The present study tested 3 different hypotheses: (1) high levels of progesterone (P(,4)) at artificial insemination (A.I.) impair ova fertilization and early embryo survival in superovulated cows; (2) bovine embryos infected by microinjection with virulent type bluetongue virus (BTV) will not survive the cytolytic effects of the virus, whereas embryos similarly exposed to (Texas A&M U. developed) attenuated BTV vaccine will; and (3) embryos collected from B. abortus culture positive cows are not infected with B. abortus. To test the 3 hypotheses: (1) mature superovulated Holstein cows were injected with P(,4), estrogen (E(,2)), or oil and embryos were collected from either right or left oviduct and uterine horn from each cow surgically (one day after estrus) and from the non-collected uterine horn nonsurgically (7 days after estrus); (2) transferable bovine embryos were microinjected with either virulent BTV, attenuated BTV vaccine, or culture medium, and the embryos were evaluated morphologically during 48 hr of culture; and (3) B. abortus experimentally challenged and culture positive two-year old cows were superovulated and their uteri were flushed nonsurgically on day 7 after estrus, when samples for B. abortus tests were taken. Results for the corresponding tested hypotheses include: (1) P levels at each of 3 A.I.'s were negatively correlated with ova fertilization rate at nonsurgical embryo collections (r = -0.56; P < 0.05); and the percentage of the total of observed sperm cells which were bound to zona pellucidas was reduced in the P(,4) injected groups (9% and 8.7%) as compared to the E(,2) injected (77% and 78%) or oil injected groups (97%); (2) embryo survival for embryos microinjected with virulent BTV was 0%, 29%, and 0% for types 10, 11, and mixture 10, 11, 13, 17, respectively; while the embryo survival for embryos microinjected with the attenuated BTV vaccine strains was 38%, 43%, and 75% for monovalents 10, 11, and quadrivalent 10, 11, 13, 17, respectively; and the embryo survival for embryos microinjected with culture medium was 42%; and (3) B. abortus was isolated from the mammary gland secretions, but not from jugular blood, cervical swabs, uterine flushings, embryos or eggs collected.