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《农业科学学报（英文版）》
>Nonphytate Phosphorus Requirement and Efficacy of a Genetically Engineered Yeast Phytase for Yellow Broilers at 22- to 42-d-Old Age
Nonphytate Phosphorus Requirement and Efficacy of a Genetically Engineered Yeast Phytase for Yellow Broilers at 22- to 42-d-Old Age
An experiment was conducted to investigate the requirement of nonphytate phosphorus(nPP) and efficacy of a genetically engineered yeast phytase(PHY A) for Lingnan yellow broilers from 22-to 42-d-old age.A total of 1 320 1-d-old male chicks were randomly divided into 11 dietary treatment groups,which consisted of 4 replicate floor pens with 30 birds per pen.The control group(treatment 1) was fed with basal diet of nPP 0.08% without dicalcium phosphate or phytase supplementation.Dietary levels of nPP were 0.16,0.24,0.32,0.40,0.48,and 0.56%,respectively,for treatments 2 to 7,through addition of dicalcium phosphate(chemistry grade) to the basal diet.Diets of treatments 8 to 11 were supplemented with PHY A at 200,400 and 600 U kg-1,a commercial phytase product(PHY B) at 400 U kg-1 level,respectively.The birds in 0.32-0.56% nPP groups gained more than those of the other groups(P<0.05).The nPP supplementation significantly improved feed intake(P<0.05).The feed gain ratio was significantly decreased by 0.40% nPP diet compared to the control birds(P<0.05).The level of 0.48% nPP was required for optimum tibia development.The additions of PHY A at 400 and 600 U kg-1 level and PHY B all significantly improved ADG(P<0.05),ADFI(P<0.05),and dry defatted tibia weight(P<0.05).Similarly,the percentage of tibia ash was increased by 600 U kg-1 PHY A supplementation(P<0.05).The requirement of nPP for maximal ADG and highest percentage tibia ash both was 0.40%.The phosphorus equivalency value of PHY A was estimated as 685 U kg-1 for male yellow broilers of 22-to 42-d-old age.
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Key Laboratory of Animal Nutrition and Feed Science South China Ministry of Agriculture/Institute of Animal Science Guangdong Academy of Agricultural Sciences Guangzhou 510640 P.R.China;
