| Two experiments were conducted to evaluate the efficiency of phytase supplementation in low-phosphorus and calcium or low protein, metabolism energy diets on performance, egg quality, bone mineralization and nutrients utilization of laying hens.1. Experiment 1:Effects of different dosage-form phytase on performance, egg quality and bone mineralization of Laying hensThis experiment was conducted to study the effect of two different dosage-form phytase(powdery and granular) on performance, egg quality and bone mineralization of laying hens. Total 1,440 30-wk-old Lohmann pink-shell hens corresponding to the egg production peak were randomly assigned to 4 treatments with 6 replicates of 18 hens for 10 wk as follows:Treatmentâ… was a positive control(PC) which was supplemented with metabolizable energy (ME) 11.53MJ/kg, crude protein (CP) 16.54%, calcium 3.55% and non-phytic phosphorus (NPP) 0.36%; Treatmentâ…¡was the negative control(NC) diet which was formulated on the basis of PC diet with Ca and NPP levels decreased to 3.45% and 0.24%(1-5wk) or 3.38% and 0.19%(6-10wk) respectively; the other two diets(Treatmentâ…¢,â…£) were supplemented with powder and granular phytase(300FTU/kg) based on Treatmentâ…¡. Results showed that feed intake, bone ash were significantly depressed(P<0.05) and cracked and broken egg ratio was increased(P<0.05) but restored by Phytase inclusion(P<0.05) in NC diet. No significant difference was observed in egg production, egg weight and egg quality in NC diet with or without phytase compared to PC diet(P>0.05). There was no significant difference between phytase powdery and phytase granular in performance, egg quality and bone mineralization (P>0.05). In conclusion, phytase supplemention had trendy to improved the performance and bone mineralization of laying hens fed low NPP diet, and no difference was observed in NC diet with phytase in form of powdery or granular.2. Experiment 2:Effects of phytase on the performance, egg quality, bone profiles and nutriments availability in laying hens fed low non-phytate P (NPP) and Ca or low ME, CP and amino acids diets.This Experiment was conducted to evaluate the effects of phytase on the performance, egg quality, bone profiles and nutriments availability in laying hens fed low non-phytate P (NPP) and Ca or low ME, CP and amino acids diets. Total 540 56-wk-old Lohmann pink-shell commercial laying hens were randomly assigned to 1 of 5 treatments with 6 replicates of 18 hens for 20 wk as follows:a positive control(PC) with CP 15.5%, ME 11.09MJ/kg, Ca 3.40%, and NPP 0.26%, the negative control 1 (NC1) diet was formulated on the basis of PC diet with Ca and NPP levels decrease to 3.30% and 0.14% respectively, the NC2 diet was formulated on the basis of NC1 diet with CP and ME decrease to 15.27%, 10.90MJ/kg respectively, two diets with addition of phytase (300FTU/kg) in NCI and NC2 diet.(1) Performance Compared to PC, ADFI of laying hens fed the NC1 diet was depressed significantly(P<0.05) and mortality was increased significantly(P<0.05). hen-housed egg production, egg number per hen-housed and ADFI were decreased (P<0.05), mortality was increased(P<0.01) significantly in NC2 diets. Compared to NCI, ADFI and final body weight were significantly increased, mortality was decreased significantly in laying hens fed NCI diet by phytase inclusion(P<0.05). Compared to NC2, hen-housed egg production, egg number per hen-housed, ADFI and final body weight were significantly increased, mortality was decreased significantly in laying hens fed NC2 diet with phytase (P<0.05). The results of egg quality showed that eggshell strength was significantly decreased in laying hens fed NCI diet compared to PC diet at 17wk, and eggshell thinkness was significantly decreased in laying hens fed NC2 diet compared to PC diet at 17wk.There were significant effects on eggshell thinkness and egg specific gravity of laying hens fed NC2 diet by phytase inclusion(P<0.05) while there were no significant effects was observed in NCI diet with phytase(P>0.05). The hen-day egg production, hen-housed production, ADFI, egg numbers per hen-housed and final body weight were significantly improved(P<0.05) when the response to phytase is predominant, and when the response to diet is predominant, no significant effect was observed in performance of laying hens. there was no interaction between diet and phytase on performance of laying hens.(2) Bone mineralization Compared to PC, the content of Ca in tibia ash was significantly decreased (P<0.05) at 17 wk, tibia ash(P=0.001) and bone breaking strength(BBS, P<0.001) were significantly decreased at 20wk in laying hens fed NC1 diets. Compared to NC1, Ca and P content in tibia ash were significantly increased(P<0.01) at 17 wk, that is to BBS(P<0.01) at 20wk by phytase inclusion in laying hens fed NC1 diet. Compared to NC2, Ca content in tibia ash at 20 wk were significantly increased(P<0.05). There had trendy to decreased the level of Ca and P in serum and alkaline phosphatase(AKP) of laying hens fed the NC groups but restored by phytase inclusion. The content of Ca and P in tibia ash at 17,20 wk and BBS at 17 wk were significantly improved (P<0.05) when the response to phytase is predominant, and when the response to diet is predominant, no significant effect was observed in of laying hens. there was no interaction between diet and phytase on bone mineralization of laying hens.(3) Nutrients availability The results of metabolic experiment showed that there were no significantly differences on nutrients availability of laying hens fed NC1 diet compared to PC. There were also no significantly difference on nutrients availability except for total energy(GE, P<0.05) availability of laying hens fed NC2 diet compared to PC. There had trendy to improve the Nitrogen(P=0.08), P(P=0.09), Ca(P=0.111) and GE(P=0.308) availability in NCI diet with phytase compared to NCI, and Nitrogen(P<0.05), phosphorus(P<0.05) availability significantly improved, Ca and GE availability were enhanced 4%,2.8% respectively in NC2 diet by phytase inclusion compared to NC2. when the response to phytase is predominant, the Nitrogen(P=0.013), P(P=0.011) availability were significantly improved, and no significant effect was observed in nutrients availability of laying hens when the response to diet is predominant or interaction between phytase and diet.In conclusion, no significant effects were observed in performance of 30-wk-old laying hens fed 0.24% or 0.19% NPP diet, and there were significant effects in bone mineralization of laying hens fed the same diet but restored by phytase inclusion (300FTU/kg). When decreased the NPP content of laying hens diet to 0.14% or decreased 0.19MJ/kg ME and 1.5% CP further, the NC1 or NC2 diet significantly depressed the performance, bone mineralization and nutrients utilization. The addition of phytase(300 FTU/kg) in NCI and NC2 diet significantly improved the performance, bone mineralization and nutrients utilization compared to the negative controls.
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