Response of broiler chickens to diets containing different levels ofsodium with or without microbial phytase supplementation

摘要

Phytate induced excessive mineral excretion through poultry litter leads to poor performance and environmental pollution. Exogenous microbial phytase supplementation to poultry diets reduce the environmental excretion of nutrient and improve bird’s performance. However, excessive dietary sodium (Na) level may hinder the phytase-mediated phytate hydrolysis and negate the beneficial effects of phytase. Therefore, this experiment was conducted to investigate the effects of different concentration dietary Na on phytase activity and subsequent impact on broiler performance, bone mineralisation and nutrient utilisation. In this study, six experimental diets, consisting of three different levels of Na (1.5, 2.5, or 3.5 g/kg) and two levels of microbial phytase (0 or 500 U/kg) were formulated by using 3 × 2 factorial design. The six experimental diets were offered to 360 day-old Ross 306 male chicks for 35 days, where, each experimental diet consisted of 6 replicates groups with 10 birds. Along with growth performance, nutrient utilization, intestinal enzyme activity, dry matter (DM) content of litter and mineral status in bone were analysed. Dietary Na and phytase had no effect on bode weight gain and feed intake. Birds on the low Na diet showed higher (p <0.05) feed conversion ratio (FCR) than the mid-Na diets. High dietary Naadversely affected (p < 0.001) excreta DM content.Phytase supplementation to the high-Na diet increased (p< 0.01) the litter ammonia content. High dietary Na with phytasesupplementation improved (Na × phytase, p < 0.05)the AME value and ileal digestibility of Ca and Mg. The total tract retention ofCa, P, and Mg was reduced with high Na diet, which was counteracted by phytasesupplementation (Na × phytase, p < 0.001). Thediets containing mid-level of Na improved (p < 0.001)the function of Na-K-ATPase and Mg-ATPase in the jejunum. The overall resultsindicate that high dietary Na did not affect phytase activity but influenced thenutrient utilization of birds, which was not reflected in bird overallperformance.