title: Supplementation of corn-soy-based diets with an Eschericia coli-derived phytase: effects on broiler chick performance and the digestibility of amino acids and metabolizability of minerals and energy.
abstract: The effect of the supplementation of diets containing low available P concentrations with low and supra-activities of an Eschericia coli 6-phytase was assessed using growing broiler chicks. A total of 384 female Ross broiler chicks were weighed at d 1 of life and assigned to 1 of 8 experimental treatments. There were 12 replicate cages with 4 chicks per cage, and the diets were fed from d 1 of life for a period of 16 d. A positive control diet (5 g/kg of available P) and a negative control diet (3 g/kg of available P) were used, and 6 more diets were manufactured by supplementing the negative control diet with 150, 300, 600, 1,200, 2,400, and 24,000 U/kg of exogenous phytase. Body weight gain and feed conversion ratios were determined, as were nutrient digestibility coefficients and toe ash values. Birds fed the negative control diet had lower (P < 0.05) weight gains than those fed the positive control diet. The addition of exogenous phytase above 150 U/kg improved (P < 0.05) weight gain, toe ash percentage, and nutrient utilization of the birds fed the negative control diet. Furthermore, the 24,000 U/kg of diet improved (P < 0.05) toe ash percentage and the utilization of several nutrients beyond that of the lower doses of phytase. It can be concluded that the supplementation of diets containing 3 g/kg of available P with exogenous phytase can improve the performance of chicks to that of birds fed a diet containing 5 g/kg of available P. In addition, the use of high doses of phytase (> 1,000 U/kg of diet) can improve nutrient availability in poultry diets beyond that of diets containing lower (< 1,000 U/kg) phytase activities. These results may be mediated partially by reduced endogenous loss as well as an increase in the availability of dietary nutrients as indicated by improvements in digestibility coefficients.
authors.affiliation: Scottish Agricultural College, West Mains Road, Edinburgh, EH9 3JG, UK.
authors.forename: A J
authors.initials: AJ
authors.lastname: Cowieson
authors.forename: T
authors.initials: T
authors.lastname: Acamovic
authors.forename: M R
authors.initials: MR
authors.lastname: Bedford
mesh_terms: D010832:6-Phytase / Q000378:metabolism / Q000494:pharmacology*; D000596:Amino Acids / Q000187:drug effects / Q000378:metabolism*; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001682:Biological Availability; D002645:Chickens / Q000254:growth & development* / Q000378:metabolism / Q000502:physiology; D019587:Dietary Supplements; D004063:Digestion; D004305:Dose-Response Relationship, Drug; D004734:Energy Metabolism / Q000187:drug effects; D005260:Female; D008903:Minerals / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism / Q000493:pharmacokinetics*; D011897:Random Allocation; D013025:Glycine max; D015430:Weight Gain / Q000187:drug effects*; D003313:Zea mays
chemical_list: D000596:Amino Acids; D008903:Minerals; D010758:Phosphorus; C028705:bone ash; D010832:6-Phytase