Phosphorus characterization in feces from broiler chicks fed low-phytate barley diets

Authors: Leytem, April; THACKER, P - UNIVERSITY OF SASKATCHEWA; TURNER, B - SMITHSONIAN RESEARCH INST

Submitted to: Journal of the Science of Food and Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2006
Publication Date: 4/11/2007
Citation: Leytem, A.B., Thacker, P.A., Turner, B.L. 2007. Phosphorus characterization in feces from broiler chicks fed low-phytate barley diets. Journal of the Science of Food and Agriculture. 87:1495-1501.

Interpretive Summary: Low phytic acid grains in poultry diets can reduce P concentrations in feces, but the influence on feces P composition is relatively unknown. We analyzed feces from poultry fed one of four barley based diets. The barley varieties used to generate the diets consisted of wild-type barley (Copeland, normal barley feed) and three low phytic acid mutant barley varieties that contained similar amounts of total P but less phytic acid. The phytic acid concentrations in the mutant barley diets were reduced by 63% (M422), 66% (M635), and 99% (M955) compared to that in the wild-type barley diet, respectively. There was little difference in digestibility coefficients for dry matter and gross energy, while P digestibility increased as the level of phytic acid in the barley diet decreased. Phosphorus concentrations were 13–30% less in feces from animals fed low phytic acid barley diets compared to those fed the normal diet. Phytic acid constituted up to 91% of the P in diet, but only 3–12% of P in the feces determined by NaOH–EDTA extraction followed by solution Phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy. Inorganic P was the major P fraction in the feces (69–75% extracted P), with a small amount of phospholipids detected in the M955 feces. This study indicates that feces from poultry fed both normal and low phytate barley diets are composed primarily of inorganic P, but there is less P excreted from birds fed a diet containing low phytate barley. Since dietary manipulation did not influence P composition of feces from birds fed barley as the primary diet ingredient, the benefits of a total P reduction from feeding low phytate barley diets are unlikely to be compromised by greater P solubility in the feces.

Technical Abstract: Low phytic acid grains in poultry diets can reduce P concentrations in feces, but the influence on feces P composition is relatively unknown. We analyzed feces from poultry fed one of four barley based diets. The barley varieties used to generate the diets consisted of wild-type barley (Copeland, normal barley feed) and three low phytic acid mutant barley varieties that contained similar amounts of total P but less phytic acid. The phytic acid concentrations in the mutant barley diets were reduced by 63% (M422), 66% (M635), and 99% (M955) compared to that in the wild-type barley diet, respectively. There was little difference in digestibility coefficients for dry matter and gross energy, while P digestibility increased as the level of phytic acid in the barley diet decreased. Phosphorus concentrations were 13–30% less in feces from animals fed low phytic acid barley diets compared to those fed the normal diet. Phytic acid constituted up to 91% of the P in diet, but only 3–12% of P in the feces determined by NaOH–EDTA extraction followed by solution Phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy. Inorganic P was the major P fraction in the feces (69–75% extracted P), with a small amount of phospholipids detected in the M955 feces. This study indicates that feces from poultry fed both normal and low phytate barley diets are composed primarily of inorganic P, but there is less P excreted from birds fed a diet containing low phytate barley. Since dietary manipulation did not influence P composition of feces from birds fed barley as the primary diet ingredient, the benefits of a total P reduction from feeding low phytate barley diets are unlikely to be compromised by greater P solubility in the feces.