Investigation of seasonal variations in cow serum retinol and β -carotene by high performance liquid chromatographic method

Abstract

1. 1. High performance liquid chromatography (HPLC) was used to determine β-carotene and retinol in cow serum. 2. 2. Two groups of state and private farm cows (Groups 1 and 2) were used to assess seasonal variation when different food sources were fed to cows on serum β -carotene and retinol concentrations. 3. 3. Mean serum concentrations of β-carotene and retinol from October to April in both Groups 1 and 2 cows were lower ( P < 0.05) than in the other months when the cows were fed various combination of maize silage, alfalfa and carrot residues and grass hay, respectively. 4. 4. Mean serum β-carotene and retinol concentrations in June and July were higher ( P < 0.05) than in other months when the cows were in pasture. 5. 5. Mean serum β-carotene and retinol concentrations in May, August and September were lower ( P < 0.05) than in June and July and higher ( P < 0.05) than in other months when a lesser amount of green pasture was available to the cows. 6. 6. There was a seasonal variation ( P < 0.05) in serum β -carotene and retinol concentrations. When the carotene intake is very high, conversion of β -carotene to retinol decreases. Mean monthly serum β -carotene and retinol concentrations showed that combination of alfalfa hay and maize silage, and grass hay and carrot residues can maintain adequate serum β-carotene and retinol concentrations during the dry season.