عنوان مقاله [English]
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<0.05), conversely serum beta carotene concentration of feedlot cattle during warm seasons was significantly higher than that in cold seasons (p<0.05). However, comparing vitamin A concentration of liver tissues of feedlot cattle in cold and warm seasons did not show any significant difference (p>0.05). ConclusionS: From the results of the present study it can be concluded that serum and hepatic concentration of vitamin A in feedlot cattle of the city of Garmsar was in normal reference range of cattle, and in spite of very low concentration of serum beta carotene concentration, due to supplementation of this vitamin in feed, vitamin A deficiency did not occur in these cattle.