Presence of fed β-carotene in digesta, excreta, blood, and hepatic and adipose tissues of Holstein steers

Eight animals were fed a diet without added β-carotene for 49 d and then supplemented with four levels of β-carotene (0, 5.5, 44 or 352 mg kg^-1 dry matter) for 30 d; the two-phase procedure was then repeated. Steers were killed at the end of the second period. Concentrations of -carotene were: 0, 0, 227.2 and 2011 μg dL^-1 (P < 0.05) in ruminai fluid; 0, 0, 533.7 and 4418 μg dL^-1 (P < 0.05) in duodenal fluid; 0, 4.03, 14.91 and 90.64 μg g^-1 (P < 0.05) in dry faeces; 0.8, 1.2, 4.7 and 8.1 μg g^-1 (P < 0.05) in liver; 0.07, 0.15, 0.5 and 3.7 μg g^-1 (P < 0.05) in subcutaneous fat; 0, 0, 0.09 and 0.23 μg g^-1 (P < 0.05) in kidney fat for dietary treatments with 0, 5.5, 44 and 352 mg β-carotene kg^-1 DM, respectively. The dose of β-carotene was reflected in retinol concentrations in liver: 101.1, 113.6, 161.7 and 199.6 μg g^-1 (P < 0.05), but not in subcutaneous or kidney fat (P > 0.1). The estimated β-carotene digestibilities were 66.25, 84.39 and 88.14% for treatments with 5.5, 44 and 352 mg β-carotene kg^-1 DM, respectively (P < 0.01). The results suggest a high capacity of bovine tissues to store β-carotene and probably a limited capability to convert β-carotene into vitamin A.