VITMAIN D3 RESPONSE IN SHEEP TO ORAL VERSUS PARENTERAL ADMINISTRATION AND TO INTRAMUSCULAR DOSE LEVELS OF VITAMIN D3

Abstract

Plasma vitamin D3 concentration changes were assessed in 10 crossbred wethers following oral or intramuscular administration of a single massive dose (5 × 106 IU) of vitamin D3. Blood plasma was taken at different times during a 3-wk experimental period. The intramuscular response was higher than the oral. In another experiment 15 ewes were administered 5 × 106 IU of vitamin D3 orally, intramuscularly, or intravenously. Blood plasma was taken at different times during a 3-wk experimental period for analyses of plasma vitamin D3 and 25-hydroxyvitamin D3. All animals were killed at the end of the experiment and vitamin D3 determinations were carried out on various tissues. Vitamin D3 given to ewes parenterally had a greater and more lasting effect on their plasma concentrations of vitamin D3 and 25-hydroxyvitamin D3 than did oral administration. While plasma vitamin D3 concentrations of the two parenteral groups were approximately equal, the plasma 25-hydroxyvitamin D3 concentrations were substantially higher in the intravenously treated group than in the intramuscularly treated group. Tissue vitamin D3 concentrations in the parenteral group were higher than in the oral group, and the adipose tissue contained higher concentrations of vitamin D3 than did other tissues. In a third experiment crossbred wethers were administered intramuscularly various amounts (5 × 106, 5 × 105, and 5 × 104 IU) of vitamin D3 in a single dose. Blood plasma was taken at different times during the subsequent 2-wk period. There was proportionality between the amount of vitamin D3 injected and plasma vitamin D3 concentration. The results suggest that parenteral administration induces both higher tissue levels and higher circulating levels of vitamin D3 than does oral administration, and that intravenous injection produces higher circulating levels of 25-hydroxyvitamin D3 than does intramuscular injection. Key words: Vitamin D3 status, sheep, oral, parenteral