Mammary transfer of vitamin A alcohol and ester in lactating dairy cows

The effect of intravenous injection of vitamin A alcohol and vitamin A ester on the vitamin A concentration of bovine milk was studied. Holstein cows received either an intravenous injection of 1 million international units (IU) of vitamin A alcohol, 1 million international units of vitamin A palmitate, or served as controls. Blood serum and milk were sampled at intervals prior to and following injection. Mean concentrations of vitamin A in milk at time 0 were 59.0, 52.0, and 58.4 mug/100 ml for the control, alcohol, and palmitate treatments. Mean contrations of vitamin A in milk, expressed as mug/100 ml or mug/g fat of cows receiving vitamin A alcohol at +195, +451, and +678 min postinjection, were greater than concentrations for either control cows or cows receiving palmitate. Partition of milk Vitamin A at +195 min postinjection for cows injected with vitamin A alcohol showed 4.1% of the recovered vitamin A in the alcohol and 95.9% in the ester form. Injection of vitamin A palmitate had little effect on milk vitamin A concentration. Vitamin A in serum (mug/100 ml) at 195 min after vitamin A alcohol injection was higher (100.4) than for either control (84.0) or cows injected with vitamin A palmitate (89.0).