Jaramillo

25-hydroxy-vitamin D3 and microbial phytase may increase digestibility of calcium and phosphorus in diets fed to growing pigs

Vitamin D regulates a wide spectrum of genes responsible for Ca and P homeostasis and cell differentiation. Cholecalciferol, commonly known as vitamin D3, is a primary source of vitamin D3 in diets for growing pigs; however, it needs to be hydroxylated twice to be active. The first hydroxylation occurs in the liver at the 25-position, resulting in 25-hydroxycholecalciferol [25(OH)D3], whereas the second hydroxylation occurs in the kidneys at the 1-position, resulting in 1,25 dihydroxycholecalciferol [1,25(OH)2D3], which is the active form of vitamin D3 in the body. Supplementation of 25(OH)D3 to diets for sows in late gestation may increase the apparent total tract digestibility (ATTD) and retention of Ca and P, but there are no data to demonstrate this effect in growing pigs.

Cereal grains commonly used in diets for pigs have low digestibility of P because P is bound to phytate. Exogenous phytase increases the digestibility of both Ca and P in pigs by releasing the P from the phytate molecule within the gastrointestinal tract of pigs. However, there is limited information about the interaction between 25(OH)D3 and supplemental phytase in diets fed to growing pigs. Therefore, the objective of this experiment was to test the hypothesis that both 25(OH)D3 and microbial phytase independently and in combination may increase standardized total tract digestibility (STTD) of Ca and P by growing pigs.

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