Effects of microbial phytase supplementation on egg production, eggshell quality, and mineral retention of laying hens fed different levels of phosphorus

A 20-wk feeding trial (21 to 40 wk of age) was conducted to evaluate the ef fects of phytase supplementation on egg production, egg quality, nutrient r etention, and P excretion of laying hens fed diets containing different lev els of P. Nine hundred and sixty ISA Brown(R) hens were randomly allocated to completely randomized block arrangement of four diets: corn-soybean diet (1.4% tricalcium phosphate, TCP) without (T1, control) and with phytase (T 2); 0.7% TCP (T3) or 0% TCP (T4) diet with phytase. Dietary microbial phyta se was added at a level of 500 U/kg. Both hen-day and hen-housed egg produc tion of T2 were significantly (P < 0.05) higher than other treatments, whic h were not different among themselves. Egg weights were also significantly (P < 0.05) different among treatments,with T2 being the highest. Feed consu mption of T2 was significantly (P < 0.05) higher than other treatments but feed conversion ratio was not significantly different from others. Specific gravity and shell thickness of the eggs were highest in the control (T1) b ut eggshell strength and broken egg to fetal egg ratio were not different a mong treatments. Haugh units were not different among treatments. Retention of Ca, P, Mg, Fe, and Zn were greater (P < 0.05) in phytase-supplemented g roups. There were significant (P < 0.05) differences in excretion of ash, P , and Zn. The excretion of these components were highest in the control, wh ereas P excretion was significantly lower in the T3 and T4 groups. In concl usion, supplementation of the microbial phytase to normal corn-soybean diet improved egg production and can reduce TCP level in the diet without affec ting egg production and egg quality. Significant reduction of P excretion c an be also achieved.