The effects of hypervitaminosis A in sheep following intramuscular administrations of vitamin A.

Ten ewe lambs (median age 11 months and average weight 29.2+/-2.5 kg) were used in the present study. They were divided into two groups: test (n=5) and control (n=5). Housing and all diets were identical. In the test group vitamin A was injected into the thigh muscle at a daily dose of 5000 IU/kg body weight for 16 days. The average final body weight of sheep in the test group was significantly (P<0.05) less than the control group. All animals were slaughtered at day 17. The lambs' feet were X-rayed to evaluate any difference for radiographic signs between test and control groups. No significant differences were seen for PCV, WBC, differential leukocyte count, and total serum protein between groups. There were no significant differences for serum AST, ALT, and ALP activities and serum calcium, inorganic phosphate, and magnesium concentrations between groups. Histological examination revealed an increased number of lipid droplets in the cytoplasm of the stellate cells of the liver in the test group. The results showed that daily administrations of vitamin A approximately 150 times greater than the daily requirement were well tolerated by sheep.