[Long-term exposure to PCB in broiler chickens--metabolic and immunotoxic effects].

Even though it has been forbidden to produce and commerically use polychlorinated biphenyls (PCB) in this country, their stocks and contaminated refuses continue to be a source of danger at present. Hence prevention of environment and food chain contamination is being focused on, along with their monitoring in various commodities. In the poultry operations random contacts of poultry with PCB-containing materials may be expected (paints, plasters, litter). In our experiment we investigated metabolic and immunotoxic effects of low PCB doses on broiler chickens. A hundred and twenty sexed straight-run chicks randomly divided themselves into three departments on deep litter. Cockerels had an ad libitum access to feeds and water, and they were reared under a continuous lighting regime. A feed mix BR-2 (ME 12.8 i.u., crude protein 19.9%) was used as an experimental diet. The experimental groups received a contaminated mix (equal portions of original commercial PCB preparations--Delor 103 and Delor 105 manufactured by the firm Chemko Strázske) at doses of 5 and 50 mg/kg. Chick exposure to PCB lasted from the first to 42nd day of their life. Chick weight, relative organ weight and vitamin A and E levels in liver were determined at the end of the experiment (42 days). The concentrations of cholesterol, triglycerides, proteins, calcium and lysozyme were determined in the blood serum. The concentrations of antibodies to chick repeated immunization with a vaccine against Newcastle disease (AVIPEST) and the blood picture of chicks were also evaluated. Chronical PCB applications in broiler diet resulted in a significant decrease in the weight of broiler chicks at the age of 21 and 28 days (P < 0.01). The weight differences were compensated later on, and the chick weight of the different groups at the age of 42 days was not significantly affected by this treatment. Hepatitis and hydropericarditis were found in affected chicks at their dissection (age of 42 days). Liver weight significantly increased after administration of both PCB doses (P < 0.01), but the relative weight of lymphoreticular organs (thymus, spleen, bursa Fabricii) decreased (P < 0.05). There were serious metabolic disorders in the blood serum after 42-day PCB applications. Cholesterol and triglyceride concentrations (P < 0.01) were significantly increasing (P < 0.01), while the content of serum calcium significantly dropped (28 and 35 days of age). PCB exposed cockerels had the significantly lower titre of antibodies to repeated immunization against Newcastle disease.(ABSTRACT TRUNCATED AT 400 WORDS)