Abstract
Changes in levels of serum and red blood cell tocopherol and serum vitamin A (retinol and retinyl palmitate) in dairy cows were examined after oral administration of vitamin AD3E premix of the liquid or rumen bypass type. In the groups administered with vitamin E 1, 000IU (dl-α-tocopherol acetate), tocopherol levels in blood did not increase. Cows administered with 6, 000IU of vitamin E of the liquid type showed significant high levels in serum and red blood cells tocopherol, but in those administered with the rumen bypass type tocopherol levels did not change. After administration with 2, 500, 000IU, 5, 000, 000IU, 7, 500, 000IU and 10, 000, 000IU of vitamin A of the liquid type, serum retinol and retinyl palmitate levels increased markedly. However, there was no significant difference in increase of serum vitamin A levels among the groups over 5, 000, 000IU of vitamin A. The cows administered with 10, 000, 000IU of vitamin A of the rumen bypass type showed a slight increase of serum levels.
It was concluded that the effective doses, which indicated the increase of blood levels after administration of vitamin A and E, were within 5, 000, 000IU of vitamin A and over 6, 000IU of vitamin E of the liquid type in cows, although there was difficulty in absorption of vitamin A and E of the rumen bypass type.
