Reevaluation of Male Broiler Zinc Requirement by Dose-Response Trial Using Practical Diet with Added Exogenous Phytase

Some reports indicate a wide range for Zn requirements for broiler chickens i.e. from ۱۰.۶ to ۱۰۵ mg kg-۱. A number of factors other than dietary Zn concentration determine the need for supplementation, principally dietary phytate. Therefore, the objective of the present investigation was reevaluation of the zinc requirement for broiler, fed practical diet supplemented with phytase in a dose-response trial. A total of ۷۶۸ male Ross ۳۰۸ broiler chicks were used. Basal corn-soy diet deficient in Zn was supplemented with experimental diets for making ۱۶ dietary treatments. Experimental design was a completely randomized design in a ۴×۴ factorial arrangement. Factors included four levels of dietary zinc (۲۴, ۵۴, ۸۴ and ۱۱۴ mg kg-۱) and phytase (۰, ۱۰۰, ۲۰۰, ۳۰۰ FTU kg-۱). Treatments were replicated four times and each had ۱۲ birds. Linear and nonlinear functions were derived for graded levels of zinc and phytase. Results indicated that effect of dietary zinc on body weight at ۴۲ days of age was significant (P< ۰.۰۱). The fitted quadratic model estimated ۶۶.۷, ۶۴.۸, and ۶۰.۱ mg kg-۱ zinc requirement for body weight at ۲۸, ۳۵, and ۴۲ days of age, respectively (P< ۰.۰۰۱), while the fitted two slope broken line estimated ۵۳.۵, ۵۳.۸ and ۵۷.۴ mg kg-۱ zinc requirement for body weight at the same ages, respectively (P< ۰.۰۰۲). Zinc equivalence value of phytase was estimated to be ۰.۲۲۵ mg kg-۱ FTU-۱ and added phytase increased liver zinc storage too (P< ۰.۰۱). Estimated zinc requirement for body weight by using practical high phytate diet, low availability source of Zn, and exogenous phytase was lower than Ross ۳۰۸ recommendation (۶۰ vs ۱۰۰ mg kg-۱).

کلیدواژه ها:

Broiler chickens ، Phytase ، Practical diet ، Requirement ، Zinc