Hypervitaminosis D₃ in broiler chicks: histopathological, immunomodulatory and immunohistochemical approach

The present study was undertaken to investigate the toxic effects of higher doses (1,00,000 IU i.e. 2.5 mg/kg body weight (BW)) of vitamin D₃, concomitantly with bacterial endotoxins (lipopolysaccharides: LPS) to study the immunomodulatory potential of vitamin D₃ in IBL-80 broiler chicks. The chicks were divided into four groups [group I (NSS), group II (LPS), group III (Vit. D₃ + NSS), and group IV (Vit. D₃ + LPS)] containing eight chicks in each group, treated accordingly for 21 days. Birds were kept under close observation for apparent clinical signs and symptoms. Clinically, vitamin D₃ treated chicks were dull, off feed, showed polydipsia, polyuria, watery faeces, rigidity of limbs, severe dehydration, weakness and significant progressive emaciation. Grossly, the bones were soft whereas most organs revealed congestion and hemorrhages in visceral organs. Histopathologically, renal tubular epithelium showed coagulative necrosis and metastatic calcification. The lung parenchyma and bronchi showed hemorrhages, congestion with diffuse heterophilic cell infiltration in inter-alveolar septa and infiltration of heterophils in alveoli along with proteinacious fluid in LPS treated chicks of treatment group, suggesting immunomodulatory action of vitamin D₃. Vitamin D₃ treated chicks showed strong expression of Calbindin D28k in intestine and kidney but weak expression in lung, which can be linked to nephrocalcinosis seen in kidney and from its prospective role in cellular calcium homeostasis.