Comprehensive
overview of phosphorus nutrition
Dr. Michael Lilburn
The Ohio State University
Efforts
to minimize the amount of phosphorus in livestock manure are increasing as the
use of the phosphorus standard for determining manure application rates
increases. Eliminating phosphorus
from the diet is not an option as it is essential for bones and teeth, cellular
membranes, protein transport, enzyme regulation, and energy, amino acid and
fatty acid metabolism. Phosphorus
digestion and absorption varies with different feeds due to variations in
phosphorus intake, calcium intake, vitamin D status, intestinal pH, age and the
intake of other minerals and dietary fats.
While phosphorus research dates back to the 1930’s, ambiguities in data exist due to a lack of recognition of variations in the liberation of phosphate groups and to differences in evaluating and reporting available phosphorus. During the last 10 years, research has focused on the addition of phytase to feeds. Phytase is an enzyme that increases the digestibility of phosphorus from the salt, phytate, by catalyzing the release of phosphate groups. The effectiveness of adding phytase to feed varies based on the endogenous phytase in the feed, intake of calcium, and origin (plant or microbial) of the phytase. Additional research is needed to compare the excretion of dry matter and phosphorus for different feedstuffs, to increase digestibility of phytase and to understand differences in the migration of organic and inorganic phosphorus in soil.