Influence of enzyme phytase supplementation on the performance of layers
D. KANNAN AND K. VISWANATHAN
Centre of Advanced Studies in Poultry Science,
VeterinaryCollege and Research Institute, Namakkal
A study was carried out to find out the effect of enzyme phytase (one gram contained 2410 IU of phytase activity) supplemented at 300, 600, 900 and 1200 IU/kg in layer chicken diets containing available phosphorus at 0.20, 0.25, and 0.30 per cent from 21 to 52 weeks of age. A control group fed with diet containing 0.50 per cent available phosphorus alone was also maintained. The inclusion of phytase in layer chicken diets improved the production parameters viz. body weight, feed consumption, feed efficiency and egg production after 40 weeks of age, when compared to their respective unsupplemented groups. The egg quality characteristics viz. specific gravity, shape index, albumen index, Haugh unit and yolk index did not show any significant difference among treatments. Where as egg weight and egg mass significantly increased after 40 weeks of age. Higher shell percentage and shell thickness of layer chicken eggs were observed in enzyme phytase supplemented groups than in unsupplemented control. The incidence of broken eggs was more pronounced in low (0.2 per cent) available phosphorus group and that could be minimized by increasing levels of phosphorus with or without phytase.
The livability of layer chicken was lower in 0.2 and 0.25 per cent available phosphorus without phytase-supplemented groups. The serum biochemical characteristics viz. serum calcium, phosphorus and alkaline phosphatase and slaughter characteristics viz. eviscerated carcass yield, ready-to-cook yield and per cent giblets yield did not differ significantly. Phytase did not influence any significant difference in tibial bone weight, tibial ash and its calcium per cent. However, significant (P<0.01) increase in phosphorus content of tibial bones was observed. Phytate phosphorus, phosphorus and calcium retention revealed significant difference among treatment groups at 52 nd week of age. But retention of dry matter, nitrogen and crude protein did not exhibit any statistical variation. Phosphorus excretion was significantly (P<0.01) reduced in phytase-supplemented groups than 0.5 per cent available phosphorus group without phytase. The net profit per egg produced was highest in 0.25 per cent available phosphorus with 300 units phytase groups (39 paise) and lowest in 0.5 per cent available phosphorus group without phytase (34 paise). Supplementation of phytase more than 300 IU/kg diet did not improve the production performance and cost effectiveness to a greater extent.