Performance and health of offspring of cows experimentally exposed to polybrominated biphenyls.

Offspring of cows experimentally given polybrominated biphenyls(fire-Master BP-6) were studied from May 1976 through January 1981. Daily doses were 0,.25, and 250 mg for 60 days for Groups I, II, and III, and 250 mg for 180 or 202 days for Group V. Concentrations of polybrominated biphenyls in fat of dosed animals in Groups I, II, and III, and V were .05, .20, 25, and 30 micrograms/g at the end of dosing. Residue concentrations in body fat declined with a half life of about 1 yr. Seventy-five calves were born to these cows and their offspring, representing first through fifth parturition. Fifteen calves died, 10 of which were in Groups III and V. All deaths in Groups III and V were attributable to dystocia. Incidence od dystocia and calf mortality were related to birth weight of the calf which in turn was correlated with concentrations of polybrominated biphenyls in blood and tissues of the dam. Other variables that influenced birth weight were sex of calf, length of gestation, and parturition number of dam. There were no significant differences in growth and performance of calves from the four dosed groups. Clinical signs of polybrominated biphenyl toxicosis were not evident, and general health of offspring was not influenced. Number of inseminations for conception was greater among offspring from Groups III and V. Mechanisms for this dysfunction have not been determined.