Assessment of bacterial phytase and citric acid concentrations on economic traits, nutrients’ digestibility and protein metabolites of broiler chickens fed diets containing marginal level of nutrients

The aim of the experiment was to study the influence of different concentrations of bacterial phytase and citric acid on growth performance, digestibility, carcase traits, meat quality and blood plasma metabolites of broiler chickens fed diets containing suboptimal level of nutrients (−100 kcal ME/kg diet, −1% CP, −0.1% Ca and −0.1% Avi. phosphorus) during 1–36 days of age in comparison of the Hubbard broiler management guide (2016). A total of 288, one-day-old Hubbard broiler chicks were wing banded and randomly distributed keeping equal initial BW in a straight run experimental design among 8 treatment groups, each containing six replicates of 6 chicks. The treatments were 8: standard diet (positive control, PC), low nutrient density diet (negative control, NC), NC + Escherichia coli phytase-6 (Phyzyme®) supplemented at 500 or 1000 U/Kg diet, NC + citric acid at 2 or 4%, NC + 500 U of phytase + 2 or 4% citric acid. In conclusion, production traits such as growth and feed conversion ratio and production index were significantly improved due to supplementation of 500 U phytase and 2% citric acid and to low nutrient density diet to the level or even better than the standard-density diet (positive control). This suggested that 500 U bacterial phytase plus 2% citric acid could allow a decrease of 0.1% in Ca and avi. P, 100 kcal/kg ME and 1% CP, respectively.