EFFECT OF A SINGLE INTRAMUSCULAR DOSE OF VITAMIN D ON CONCENTRATIONS OF LIPOSOLUBLE VITAMINS IN THE PLASMA OF HEIFERS WINTER-FED OAT SILAGE, GRASS SILAGE OR HAY

Abstract

Blood profiles for 25 hydroxyvitamin D (250HD), vitamins A and E, calcium, phosphorus and magnesium in three groups of Shorthorn heifers winter-fed either oat silage, grass silage or hay have been established. In each dietary treatment, half of the animals were injected with a single intramuscular dose of vitamin D3 (1 000 000 IU). The injections increased plasma 250HD levels (ng/mL) at the end of the experiment from 35 to 44 for oat silage, from 35 to 75 for grass silage and from 29 to 40 for hay. The plasma 250HD in the oat silage-fed heifers approached levels that were suggestive of vitamin D deficiency. 250HD plasma levels of cattle on grass silage were more responsive to the vitamin D treatment than those on oat silage or hay. Plasma levels of vitamin A at the end of the experiment (134 day s) were significantly higher (P < 0.01) in the silage-fed animals than in the hay-fed animals. The vitamin D-treated heifers fed oat silage had higher (P < 0.05) blood vitamin E levels than the other heifers. Plasma calcium, phosphorus and magnesium levels appeared to be unaffected by diet or vitamin D treatment. Greater weight gains were observed in heifers on hay than in those on grass silage or oat silage. Weight gains tended to be higher (NS) in the vitamin D-treated heifers fed oat silage than in those that were not treated. Gains were also higher (P < 0.05) with the hay than with the silage diets.