236 NORMAL REPRODUCTIVE CAPACITY OF HEIFERS RESULTING FROM TRANSFER OF IN VITRO-FERTILIZED EMBRYOS CULTURED WITH AN ANTIVIRAL COMPOUND

Abstract

Bovine viral diarrhea virus (BVDV) replicates in embryo culture systems and remains associated with developing IVF bovine embryos despite washing and trypsin treatment. Previous research (Givens et al. 2006 Theriogenology 65, 344–355) determined that 2-(4-[2-imidazolinyl]phenyl)-5-(4-methoxyphenyl)furan (DB606) can be added to an in vitro embryo production system to prevent replication of BVDV without inhibiting embryonic development. The objective of this research was to assess sexual development and future reproductive capacity of heifers resulting from embryos that had been exposed to DB606 while developing in vitro. Presumptive zygotes that resulted from in vitro fertilization of oocytes were cultured for 7 days in medium supplemented with 0.4 µM DB606 or medium lacking the antiviral agent. All blastocysts were individually transferred nonsurgically into the uterus of a synchronized recipient. Additional control pregnancies were established by natural breeding. At 20 to 27 months of age, 7 heifers resulting from each treatment were simultaneously exposed to a fertile bull in a single pasture during a 63-day breeding season. All but 2 heifers subjected to natural breeding were pregnant 28 days after removal of the bull. One pregnancy was aborted between 5 and 7 months of gestation from a heifer that had undergone IVF without exposure to DB606. All offspring were normal upon clinical observation at birth. One heifer resulting from IVF with exposure to DB606 would not allow its calf to nurse adequate quantities of colostrum; thus, this calf was removed from the study. Adjusted 205-day weaning weights for offspring were evaluated using ANOVA and Tukey Kramer test for pair-wise comparisons. Offspring of dams treated or untreated with DB606 during IVC or produced by natural breeding exhibited mean adjusted 205-day weaning weights of 194, 181, and 170 kg, respectively (not significantly different). Results of this research using a limited number of animals demonstrates that exposure to DB606 during the first 7 days after fertilization does not appear to cause delayed toxic effects that would impair the future reproductive capacity of heifers.