Dietary 1α-hydroxyvitamin D3 increases the concentration of phosphorus in the plasma of ewes

Vitamin D metabolites provide a novel method to increase the efficiency of bodily phosphorus (P) and calcium (Ca) use by increasing absorption and retention along with inducing bone remodelling and deposition. These compounds may have potential application for livestock where P demand is high and in grazing environments that are deficient in P. The non-endogenous compound 1α-hydroxyvitamin D3 (1(OH)D3) utilised in the treatment of human osteoporosis bypasses the tightly regulated step of 1α-hydroxylase in the kidney to create the active hormone form of the vitamin, 1,25α dihydroxyvitamin D3. The few available ruminant studies have shown that it has a positive effect on blood P and Ca status but studies have been restricted to intramuscular injection over a relatively short period of time (Sachs et al. 1987; Naito et al. 1987; Braithwaite 1980). It was hypothesised that dietary 1(OH)D3 supplementation would have a positive and sustained effect on plasma phosphorus concentrations over an 84-day period, utilising sheep as a model ruminant.