Effects of dietary supplementation of citric acid, copper, and microbial phytase on growth performance and mineral retention in broiler chickens fed a low available phosphorus diet

SUMMARY An experiment was conducted to study the effects of microbial phytase (PHY), citric acid (CA), and Cu proteinate supplementation in broilers (13 to 42 d of age) fed a low available P diet (0.25%) on growth performance, carcass characteristics, blood parameters, and mineral retention. A 2 × 2 × 2 factorial arrangement of treatments was used to evaluate 2 levels of PHY (0 and 750 phytase units/kg of diet), Cu (0 and 250 ppm), and CA (0 and 3%). The CA and Cu supplementation as well as their interaction significantly affected BW and BW gain (P < 0.05), with birds fed supplemental CA having better BW gain when fed the Cu-supplemented diet. A significant Cu × CA interaction (P < 0.05) was observed for tibia weight, in which CA supplementation resulted in increased tibia weight when birds were fed a diet not supplemented with Cu. Interaction effects between PHY and Cu were noted for tibia ash (P < 0.01) and tibia P (P < 0.05), with Cu + PHY supplementation being superior to the other treatments for tibia ash. However, tibia P was greater for the individual effects of both Cu and PHY compared with the combined effect of both additives. There was a significant interaction (P < 0.01) of PHY and CA supplementation with tibia ash percentage, in which the tibia ash (%) increased with combinations of PHY and CA. Supplementation with Cu also resulted in significantly lower cholesterol levels in the thigh muscle (P < 0.05) and serum of birds (P < 0.05). Regarding the main effects of microbial phytase (P < 0.01) and CA (P < 0.05), supplementation increased the P retention with both additives. Therefore, when a low available P diet is used after 13 d, supplementing these additives in the formulation should be considered.