Effects of Total Phosphorus and High-Dose Phytase in Feed on Growth Performance and Physicochemical Indicators of Small White Feathered Broilers

Shao Bing; Yan Peipei; Liang Yongli; Dong Yilei; Liu Xuelan; Fu Chunyan; Zhang Heng; Li Xia; Shi Tianhong

doi:10.14083/j.issn.1001-4942.2025.03.023

Abstract：A total of 1 080 one-day-old'Yisheng 909'small white feathered broilers were selected and randomly allocated to nine groups with six replicates to study the effects of different levels of total phosphorus(TP)and high doses of phytase in feed on growth performance and physicochemical indexes.The nine treat-ments included control(TP 0.68％for 1～21 days and 0.65％for 22～42 days,available phosphorus 0.45％for 1～21 days and 0.40％for 22～42 days,no phytase),four non-phytase treatments(TP 0.35％,0.40％,0.45％and 0.50％for 1～42 days),and four phytase treatments(TP 0.35％,0.40％,0.45％and 0.50％for 1～42 days,phytase 5 000 FTU/kg).There were twenty broilers per replicate with half female and half male ones.The results were as follows.(1)For the four non-phytase treatments,the daily weight gain and feed con-sumption at 1～21 days and 22～42 days of age increased significantly with the increase of TP,but were all significantly lower than those of the control(P＜0.05);the feed-weight ratio at 1～21 days of age was signifi-cantly higher than that of the control(P＜0.05)except the 0.50％TP treatment;the mortality rates of the 0.35％and 0.40％TP treatments at 1～21 days of age showed the increasing trend compared to the control(0.05 ≤P＜0.10);the serum phosphorus level at 21-day old was significantly lower than that of the control(P＜0.05),and at 42-day old,the serum phosphorus level and tibia ash were significantly lower than those of the control(P＜0.05)except for the 0.50％TP treatment.(2)For the four phytase treatments,the daily weight gain at 1～21 days and 22～42 days of age were higher or significantly higher(P＜0.05)than that of the control,while the feed-weight ratio and mortality rate had no significant differences with the control;the serum phosphorus of the treatments with 0.40％or more TP at 21-day old,and the serum calcium,phosphorus and alkaline phosphatase and the tibia ash contents at 42-day old had no significant differences with the control.(3)The activity of amylase,trypsin and lipase in the duodenum had no significant differences among all treat-ments at 42-day old.(4)The fecal phosphorus level significantly increased with the increase of TP level in feed in both non-phytase treatments and phytase treatments(P＜0.05),but had no significant difference be-tween non-phytase treatments and phytase treatments with the same dietary TP;fecal copper,iron,manganese and zinc contents had no significant differences among all treatments when broilers aged 42 days.It could be seen that a diet with TP below 0.50％and without phytase cannot meet the phosphorus need of small white feathered chickens;when the diet contained 5 000 FTU/kg phytase,0.40％TP for 1～21 days and 0.35％TP for 22～42 days could meet the phosphorus need of small white feathered chickens,which could save 94％of feed calcium hydrogen phosphate dosage and reduce 65％of fecal phosphorus content compared to the control.