study on the serum and liver concentrations of vitamin a and beta carotene in feedlot cattle: a field study in the city of garmsar

background: vitamin a is a lipid soluble vitamin which can be stored in the body organs (especially in liver) and its supply is only through ration. objectives: the present study has been conducted to evaluate vitamin a status of feedlot cattle in the city of garmsar and impact of season and nutritional management on it. methods: during the study 100 blood samples were taken from feedlot cattle of 6 farms in cold seasons of one year and 100 samples from 5 farms in warm seasons of the same year. also, 50 blood and liver samples of slaughtered feedlot cattle were taken from garmsar slaughter house in each of the mentioned seasons. serum and hepatic tissue concentrations of vitamin a and beta carotene were measured by using standard biochemical methods. student’s t-test and tukey’s hsd tests were used for analysis  of the results and  presults: the results of present study showed that mean serum and hepatic concentration of vitamin a in feedlot cattle in the city of garmsar was in defined normal range for cattle and these animals did not show any vitamin a deficiency, but mean serum beta carotene concentration was at a very low level and lower than defined normal range for this species. mean serum vitamin a concentration of feedlot cattle in cold seasons was significantly higher than that in warm seasons (p