Long-Term Performance and Health of Cows Experimentally Exposed to Polybrominated Biphenyls

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Abstract
Holstein cows (15) were studied for up to 1500 days to determine whether exposure to polybrominated biphenyls (PBB) produced latent or subtle toxicosis not evident in previous acute or short studies. Animals came from 3 groups given 0, 0.25 or 250 mg of Firemaster BP-6/day for 60 days in 1975. Another group that received 250 mg BP-6 for 180 or 202 days in 1976 was also studied. Individual animals were in 2nd, 3rd or 4th lactations. Milk production was not different among experimental groups and mature body weights were similar. Increases in amount or duration of exposure did not increase number of infections, dysfunctions or general injuries. Exposure to 250 mg/day for 60, 180 or 202 days increased frequencies of reproductive disorders at parturition, particularly related to and following a high incidence of dystocia. A contributing factor to dystocia was larger birth weights of calves from cows exposed to 250 mg daily compared to calves from cows exposed to 0 or 0.25 mg PBB. Although reproductive dysfunctions required more veterinary care, numbers of services per conception were not different among groups.