Rahul Kumar*, Harmanjit Singh Banga,and Rajinder Singh Brar
Department of Veterinary Pathology, College of Veterinary Science, Guru Angad Dev Veterinary and Animal Sciences University (GADVASU),Ludhiana-141004, Punjab, India
Introduction:Vitamin D3is used as a supplement in the feeds of livestock, pets, and human infants. However, the presence of excessive Vitamin D3 has been shown to cause toxicity in humans and animals. This study investigatedthe clinicopathological aspects of Vitamin D3toxicity in broilerchickens.Materialsandmethods:The median lethal dose(LD50) of Vitamin D3was estimated by the up-and-down method.To determine long term (21 days) toxic effects of oral Vitamin D3 supplementation,90 (14-day-old) IBL-80 unsexed chicks were randomly divided into three groupsasA (control, received basal diet), B (basal diet + Vitamin D3at 16.67 mg/kg body weightdaily), and C (basal diet + Vitamin D3at 33.33 mg/kg body weightdaily).Results:The findings indicated that broiler chickens tolerated a single oral doseof Vitamin D3up to 550 mg/kg body weight(22,000,000 IU/kg) without mortality. The results of long-term (21 days) oral supplementation of divided dosesof Vitamin D3in broiler chickens (groupsB and C) showed progressive emaciation, elevated hemoglobin,hypercalcemia, hypophosphatemia,and increased alkaline phosphatase activity. At necropsy, pale liver and kidneys, congestion and hardening of lungs, mild congestion in the brain,and soft bones were observed in Vitamin D3treated chicks (groupsB and C). Microscopically, degeneration and metastatic calcification in lung parenchyma and peribronchiolar epithelium, coagulative necrosis and calcification in kidneys,and calcification with fibroplasia in proventriculus weredetected. Lungs and kidneys showed a significantdifference in calcification score between groups B andC. Broiler chickens from Vitamin D3treated groups (B and C) showed strong immunohistochemical expression of Calbindin D28K in the intestine and kidneys but weak expression in the lungs.Conclusion: This study demonstrates that broiler chicks can tolerate very high levelsof a single oral dose of Vitamin D3.Toxic effects of prolonged exposure toVitamin D3are due to over-expression of Calbindin D28k in the intestine and kidneys,disturbing the calcium and phosphorous homeostasis and leading to metastatic calcification of vital organs. This study supports that prolongedover-supplementation of Vitamin D3causes toxic effects;hence,appropriate dietary VitaminD3 supplementation limitsshould be set.