Polybrominated biphenyl (PBB) in the growing pig diet

Twelve pigs which averaged 13.7 kg were randomly allotted from litters to a corn-soybean meal grower diet containing 0, 20, or 200 ppm of polybrominated biphenyls (PPB). During a 16-week growth trial, average daily gain (kg), average daily feed (kg) and feed/gain for pigs on diets containing 0, 20, or 200 ppm of PBB, respectively, were 0.82, 2.45, 2.99; 0.67, 1.88, 2.79; 0.45, 1.23, 2.70. Mean daily gain differences between all lots were highly significant (p < 0.01). Blood from each pig was withdrawn biweekly through the first 8 weeks of the trial and at 4 week intervals thereafter. Hemoglobin and hematocrit differed significantly only at the 6 weeks bleeding, being reduced in pigs receiving 200 ppm of PBB. Erythrocyte reduced glutathione concentration and glutathione peroxidase activity were not significantly influenced by level of dietary PBB. Serum lactic dehydrogenase activity was significantly higher in control pigs than in either PBB supplemented lots at 16 weeks. There was no significant influence of PBB upon serum glutamic oxaloacetic transaminase, serum alkaline phosphatase or serum creatine phosphokinase. Based on these enzyme assays, PBB produced no evidence of significant necrosis of liver, myocardium, or skeletal muscle. There was no consistent effect of dietary PBB upon total serum protein concentration or electrophoretic profile. Pigs on either level of PBB did not have overt clinical signs of toxicity during the 16-week test period with the exception of a dermatosis on the ventral surface of two of the pigs receiving 200 ppm of PBB. There was a marked increase in liver weight of pigs receiving either level of dietary PBB. Heart, kidney, and adrenals of pigs receiving either level of dietary PBB were heavier as a percent of body weight than that of control pigs. Fat retention of PBB and urinary and fecal PBB excretion were significantly affected by dietary PBB level. Grossly, the glandular portion of the stomach appeared somewhat hyperplastic in pigs on 200 ppm of PBB. Two pigs which had received 200 ppm of PBB were placed on the control diet and over the next 14 weeks normal growth rate occurred. One of these pigs was killed and organ weights were normal. The other pig, a gilt, came into estrus. She was bred and conceived. At the end of gestation, four pigs were born. Three survived and grew normally; the one death at birth examined at gross necropsy did not reveal changes in organ size or other tissue alterations.