Effects of PBBs on cattle. I. Clinical evaluations and clinical chemistry.

Toxicosis was induced in pregnant heifers by feeding 25,000 mg/head/day of FireMaster BP-6, a commercial blend of polybrominated biphenyls (PBB). The PBB feeding decreased dry matter intake approximately 50% by 4 days exposure. Emaciated animals became anorexic a few days prior to death at 33 to 66 days. Weight losses of heifers average 80 kg. Other clinical signs observed were dehydration, diarrhea, excessive salivation and lacrimation, fetal death, abortion, and general depression as evidenced by depressed heart and respiratory rates. Clinical signs were apparent after 10 days exposure and progressively intensified along with loss of condition until death. Clinicopathologic changes included significantly increased serum glutamic-oxaloacetic transaminase and decreased serum calcium by 30 days exposure. Lactate dehydrogenase, urea nitrogen, and bilirubin were elevated, and serum albumin decreased by 36 to 40 days. Principal urine changes were decreased specific gravity and moderate proteinuria. Pregnant heifers fed 0.25 or 250 mg/head/day for 60 days and nonpregnant heifers fed 250 mg/head/day for 180 days displayed neither clinical signs nor clinicopathologic changes indicating adverse effects from PBB exposure. Post-exposure, all heifers exposed to PBB for 60 days calved normally with zero calf mortality and were successfully rebred. Milk production was not different from control animals. Birth weights of calves from dams exposed to 250 mg PBB/head/day were significantly greater than calves of dams exposed to 0 mg or 0.25 mg/head/day. PBB exposure of dams produced no detrimental effects on calves as indicated by clinical signs, clinicopathologic changes, or performance.