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ARS Home » Pacific West Area » Kimberly, Idaho » Northwest Irrigation and Soils Research » Research » Publications at this Location » Publication #220398
Title: Phosphorus utilization and characterization of ileal digesta and excreta from broiler chickens fed diets varying in cereal grain, phosphorus level, and phytase addition

Author
item Leytem, April
item WIDYARATNE, G - UNIV. OF SASKATCHEWAN
item THACKER, P - UNIV. OF SASKATCHEWAN

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2008
Publication Date: 12/1/2008
Citation: Leytem, A.B., Widyaratne, G.P., Thacker, P.A. 2008. Phosphorus utilization and characterization of ileal digesta and excreta from broiler chickens fed diets varying in cereal grain, phosphorus level, and phytase addition. Poultry Science. 87(12):2466-2476.

Interpretive Summary: Cereal grains based feeds fed to poultry contain both endogenous and can contain exogenous phytase which affect not only the amount of phosphorus (P) utilized in the diet but the amount and form of P excreted by the birds which ultimately affects it solubility once land applied. The effects of both endogenous and exogenous phytase in a variety of cereal grain based diets on P retention and P solubility of manures were tested with twelve dietary treatments fed to broiler chicks for twenty-one days. Treatments consisted of four cereals (corn, wheat, barley, oat), and three P treatments (low P (0.30% available P), low P + phytase, high P (0.45% available P)) in a randomized design. Ileal samples were collected at 21 days to determine P retention by the birds and fresh manure was collected at 20 and 21 d to determine P characteristics and solubility of the manures. Ileal and manure samples were analyzed for total P and Ca, with P composition determined by solution 31P NMR spectroscopy. Manure samples were also analyzed for water soluble P (WSP). There was a large range in phytate P utilization by the birds (measured at the terminal ileum) with phytate P digestibility ranging from 3 to 42%, while ileal P digestibility ranged from 56 to 71%. Diets having exogenous phytase supplementation had a 98% greater phytate P digestibility than non-amended diets, while endogenous grain phytase activity had no effect on phytate P digestibility. The total tract digestibility for phytate P and P ranged from 10 to 73% and 43 to 61%, respectively. There was an average increase in total tract phytate P digestibility of 198% when diets were supplemented with phytase. The P composition of the ileal digesta was dominated by phytate P which ranged from 70 to 88% of total P, while in the manure phytate P ranged from 26 to 76% of total P. Manure WSP ranged from 3.2 to 7.5 g/kg and was greatest in the barley diets. There was a 25% reduction in manure WSP from the high P to the low P + phytase diets and a 37% reduction from the high P to the low P diets. As cereal grain had little influence on phytate digestibility it is unlikely that endogenous grain phytase activity has much influence on overall phytate utilization by poultry. Both manure total and WSP were reduced by feeding either a low P diet or a low P diet with phytase addition, irrespective of cereal grain, which reduces the risk of P transfer to water bodies once manures are land applied.

Technical Abstract: Both endogenous and exogenous phytase present in poultry feeds can alter phytate utilization as well as the solubility of phosphorus (P) excreted, which can be a concern from an environmental perspective. To address the effects of endogenous phytase present in cereal grains and exogenous phytase additions on P solubility of manures, twelve dietary treatments were fed to broilers for 21 d. Treatments consisted of four cereals (corn, wheat, barley, oat), and three P treatments (low P (0.30% AvP), low P + phytase, high P (0.45% AvP)) in a randomized design. Fresh manure was collected at 20 and 21 d and pooled by pen. Ieal samples were collected at 21 d. Ileal and manure samples were analyzed for total P and Ca, with P composition determined by solution 31P NMR spectroscopy. Manure samples were also analyzed for water soluble P (WSP). Apparent ileal digestibility coefficients for phytate P and P ranged from 0.03 to 0.42 and 0.56 to 0.71, respectively. Diets having exogenous phytase supplementation had a 98% greater phytate P digestibility, although endogenous grain phytase activity had no effect on phytate P digestibility. Apparent total tract digestibility coefficients for phytate P and P ranged from 0.10 to 0.73 and 0.43 to 0.61, respectively. There was an average increase in total tract phytate P digestibility of 198% when diets were supplemented with phytase. The P composition of the ileal digesta was dominated by phytate P which ranged from 70 to 88% of total P, while in the manure phytate P ranged from 26 to 76% of total P. Manure WSP ranged from 3.2 to 7.5 g/kg and was greatest in the barley diets. There was a 25% reduction in manure WSP from the high P to the low P + phytase diets and a 37% reduction from the high P to the low P diets. As cereal grain had little influence on phytate digestibility it is unlikely that intrinsic grain phytase activity has much influence on overall phytate utilization by poultry. Both manure total and WSP were reduced by feeding either a low P diet or a low P diet with phytase addition, irrespective of cereal grain, which reduces the risk of P transfer to water bodies once manures are land applied.