The role dietary phosphorus may play in subclinical hypocalcemia and milk fever prevention: new research

Traditionally, milk fever prevention programs have attempted to directly alter Ca status of dairy cows at calving. Common approaches include feeding pre-fresh dairy cows diets containing anionic salts, restricting dietary Ca, feeding hyper-dietary Ca and administering Ca boluses. There is an abundance of research in regard to the mechanisms associated with dietary Ca alteration, dietary cation-anion difference as related to parathyroid hormone and vitamin D and the role they play in the prevention of hypocalcemia and milk fever in dairy cattle. Over the past decade new research has also better-defined phosphorus homeostasis in animals. This research has defined a negative relationship between dietary P and blood Ca status at calving in dairy cows. Specifically, lower blood Ca has been observed when excessive or high levels of dietary P are fed. It is now understood that fibroblast growth factor 23 (FGF-23), a peptide hormone active in bone tissue, also regulates bone resorption of Ca and P and urinary retention of P. While research evidence is indirect, new feeding strategies, such as feeding Zeolite A, have emerged, which capitalize on P homeostasis as an alternative to improve Ca status of dairy cows at calving. This presentation will focus on supportive research and the practical aspects of this research.

Keywords: milk fever, phosphorus, FGF-23, Zeolite A.