# Phosphorus Metabolism and Function in Ruminants: Current Knowledge

## TL;DR

This paper reviews how phosphorus metabolism works in dairy cattle, focusing on its role in health, productivity, and environmental impact.

## Contribution

The paper provides an updated review of phosphorus regulation in ruminants, emphasizing hormonal control and clinical implications of deficiency.

## Key findings

- Phosphorus deficiency in dairy cows is linked to reduced milk yield, anemia, and muscle weakness.
- Postpartum hypophosphatemia can lead to serious conditions like hemoglobinuria and recumbency.
- FGF23 plays a key role in regulating phosphorus metabolism in cattle.

## Abstract

Phosphorus is an essential mineral that supports bone formation, energy metabolism, and normal muscle and nerve function in dairy cattle. Around calving, cows often experience a negative energy and mineral balance, which may lead to a drop in blood phosphorus levels, known as hypophosphatemia. This condition can cause weakness, loss of appetite, anemia, and decreased milk production. If left untreated, it may progress to serious disorders such as postpartum hemoglobinuria or downer cow syndrome. This review explains how phosphorus metabolism is regulated in the body, especially by hormones such as parathyroid hormone, vitamin D, and Fibroblast Growth Factor 23 (FGF23). It also highlights how phosphorus deficiency affects red blood cells and immune function, and discusses practical ways to monitor and prevent it through proper feeding strategies. Understanding and managing phosphorus balance is crucial for maintaining the health, welfare, and productivity of dairy cows.

Phosphorus (P) is a key macromineral essential for numerous physiological processes, including energy metabolism, skeletal mineralization, and cellular signaling. In dairy cattle, its homeostasis is tightly regulated by parathyroid hormone, calcitriol, and fibroblast growth factor 23 (FGF23). Phosphorus deficiency is common during the transition period and is associated with reduced milk yield, anemia, muscle weakness, and immunosuppression in severe or prolonged cases. This review summarizes the current understanding of phosphorus metabolism in ruminants, emphasizing differences from monogastric species, hormonal regulation, and the clinical manifestations of deficiency. Particular attention is given to postpartum hypophosphatemia, its relationship with acute-phase proteins, and the pathogenesis of postpartum hemoglobinuria and recumbency. The review also discusses diagnostic methods for assessing phosphorus status, recent findings on FGF23 physiology in cattle, and including demonstrated effects of phosphorus imbalance on periparturient immune suppression and increased environmental phosphorus losses through manure. Maintaining optimal phosphorus nutrition is crucial for bovine health, productivity, and reduction in environmental phosphorus losses.