Abstract: An experiment was conducted to study the effect of microbial phytase (phyzyme XP5000G) supplementation in broiler chicks' diets on the performance, serum total protein (TP), minerals (Ca, Mg and P) and the serum enzyme activities (AST, ALT, LDH). A reference diet adequate in calcium and non-phytate phosphorus (10.0 gkg-1 Ca and 5 gkg-1 nPP) and two deficient diets in Ca and nPP (8.5 gkg-1Ca and 3.5 gkg-1 nPP, and 7.5 gkg-1 Ca and 2.5 gkg-1 nPP) with or without phytase (0 and 100mgkg-1) were offered to broiler chicks from 1 to 21 days of age. Although the low-nPP diets had no significant effect on body weight gain (BWG) of chicks (p>0.05) They increased (p<0.01) feed intake (FI) and feed conversion ratio (FCR) when compared to the low-nPP diet supplemented with enzyme. Phytase had a favorable effect, although non-significantly, on BWG of chicks fed very low level of nPP. Enzyme reduced the feed intake (p<0.05) and improved the FCR of Ca-nPP deficient chicks (p<0.01). The decrease in Ca-nPP content in the diet caused a significant increase in serum concentration of Ca (p< 0.05) and decrease in P concentration (p< 0.05). Low Ca-nPP diets had no influence on serum Mg concentration. Dietary phytase reduced the Ca level and increased the P level (p<0.05) of serum in chicks fed with Ca-nPP deficient diets. The activity of LDH increased (p<0.01) in response to low dietary Ca and nPP, deficient but there was no influence on serum ALT and AST activity and TP content (p>0.05). Phytase supplementation reduced serum ALT (p<0.05) and had no effect on AST (p>0.05). Serum LDH activity further increased (p<0.01) by phytase supplementation. These results demonstrated that the performance of the chicks received low levels of Ca and nPP with phytase was improved and the serum parameters were comparable to those chicks fed with normal Ca-nPP diet.
Key words: phytate phosphorus, phyzyme, broiler performance