Gorgan University of Agricultural Sciences and Natural Resources Poultry Science Journal 2345-6604 3 1 2015 06 23 Effect of Phytase Superdoses and Citric Acid on Growth Performance, Plasma Phosphorus and Tibia Ash in Broilers Fed Canola Meal-Based Diets Severely Limited in Available Phosphorus 27 36 2325 10.22069/psj.2015.2325 EN HR Taheri Department of Animal Science, Faculty of Agriculture, University of Zanjan, Zanjan, Iran. S Taherkhani Department of Animal Science, Faculty of Agriculture, University of Zanjan, Zanjan, Iran. Journal Article 2014 09 29 This experiment was conducted to investigate the effect of phytase superdoses alone or in combination with citric acid (CA) in canola meal-based diets severely limited in available phosphorus (P_a) on growth performance, plasma phosphorus (P), and tibia ash (TA) in broilers from 22 to 42 d of age. Two hundreds and eighty 21-d-old male broilers were used in 28 pens of 10 birds per each. The experimental diets consisted of a positive control (PC) diet and six negative control (NC) diets which consisted of two levels of CA (0 and 20 g/Kg) and three levels of phytase (0, 1000 and 4000 U/Kg) in a 2 × 3 factorial arrangement. The PC diet contained 4.3 g/Kg P_a, but all NC diets contained 1.5 g/Kg P_a. Results indicated that the birds fed the PC diet had a significantly higher average daily gain (ADG), plasma P and TA, but a lower feed conversion ratio (FCR) than those fed the NC diet. The ADG, FCR and plasma P values in birds fed NC diets supplemented with 4000 U/Kg phytase enzyme (with or without CA) significantly reached those of birds fed the PC diet. But, addition of phytase enzyme at 1000 U/Kg only plus CA to the NC diet could significantly improve FCR and plasma P. A significant interaction was observed between phytase and CA for FCR and plasma P. Although TA values in NC + 1000 U/Kg phytase treatments (with or without CA) were similar to the PC treatment, TA values of NC + 4000 U/Kg phytase treatments (with or without CA) was greater than that of the PC treatment. Results of this study showed that, in severely limited P_a corn-canola meal-based diets, supplementing 4000 U/Kg phytase or also 1000 U/Kg phytase plus CA will be sufficient to obtain the comparable feed efficiency in broilers to those fed the adequate P_a diet. https://psj.gau.ac.ir/article_2325_ec62dadffca65eef847d47aec0aca439.pdf