[ effect of different levels of cadmium on the histopathological changes and the rate of lymphoid cells apoptosis of bursa of fabricius in broiler chickens]

ABSTRACT

Cadmium toxicity can cause kidney failure, liver damage and a weakened immune system in experimental and naturally occurring toxicities. This study was designed to investigate the effects of cadmium [Cd] on the histology and the rate of lymphoid apoptosis in the bursa of fabricius of chicken. One-hundred 20-day-old male Ross broilers were purchased and randomly divided into four groups. The control group [C] received no Cd, whereas groups 1, 2, and 3 had rations administered containing 25, 50 and 100 ppm cadmium as CdCl, respectively. At days 14, 28 and 42, seven chicks from each group were randomly selected and sacrificed. The bursa of Fabricius of each chick was removed, weighed, fixed in 10% buffered formalin and processed for histopathology and assessment of the rate of lymphoid cells apoptosis. The apoptotic cells were demonstrated in paraffin embedded tissue sections using the TUNEL[terminal oxynucleotidyl transferase-mediated dUTP nick end labeling] method. The concentration of Cd in the liver samples was measured by atomic absorption. Areverse correlation between the levels of Cd in the rations and the body weight of the chickens [p < 0.01] was found. The concentration of Cd in the liver showed a positive correlation with the levels of Cd in the rations [p < 0.01]. The number of apoptotic lymphoid cells was significantly increased in those groups receiving higher levels of Cd [especially groups 2 and 3] [p<0.01]. Morphologically, plicas and lymphoid follicles of groups 2 and 3 were smaller than of the control group. In the histological analysis they were found to be hypocellular and some of them were edematous. Compared to the control group, there was an increase in the number of intraepithelial cysts in groups 2 and 3 at days 28 and 42. In addition, atrophic changes of bursal paranchyma were observed in group 3 after 42 days. It can be concluded that under experimental conditions the higher concentrations of Cd in the rations [50 and 100 ppm]has detrimental effects on the bursa of Fabricius of chickens