Dietary Phytase and Lactic Acid-Treated Cereal Grains Differently Affected Calcium and Phosphorus Homeostasis from Intestinal Uptake to Systemic Metabolism in a Pig Model

High intestinal availability of dietary phosphorus (P) may impair calcium (Ca) homeostasis and bone integrity. In the present study, we investigated the effect of phytase supplementation in comparison to the soaking of cereal grains in 2.5% lactic acid (LA) on intestinal Ca and P absorption; intestinal, renal, and bone gene expression regarding Ca and P homeostasis; bone parameters; and serum levels of regulatory hormones in growing pigs. Thirty-two pigs were randomly assigned to one of four diets in a 2 × 2 factorial design in four replicate batches for 19 days. The diets comprised either untreated or LA-treated wheat and maize without and with phytase supplementation (500 phytase units/kg). Although both treatments improved the P balance, phytase and LA-treated cereals differently modulated gene expression related to intestinal absorption, and renal and bone metabolism of Ca and P, thereby altering homeostatic regulatory mechanisms as indicated by serum Ca, P, vitamin D, and fibroblast growth factor 23 levels. Moreover, phytase increased the gene expression related to reabsorption of Ca in the kidney, whereas LA-treated cereals decreased the expression of genes for osteoclastogenesis in bones, indicating an unbalanced systemic availability of minerals. In conclusion, high intestinal availability of dietary P may impair Ca homeostasis and bone integrity.