Combined effects of dietary phytase and organic acid on growth and phosphorus utilization of juvenile yellow catfish Pelteobagrus fulvidraco

Abstract

This experiment was conducted to evaluate the combined effects of organic acid and phytase on the digestibility coefficients, growth performance, body composition, vertebral and serum mineral contents, and liver and serum antioxidant properties in juvenile yellow catfish. This experiment was conducted using 900 juvenile yellow catfish in a completely randomized design with a 3 × 2 factorial arrangement (0, 2, and 4 g kg− 1 feed organic acid and 0 and 0.2 g kg− 1 feed (1000 IU kg− 1 feed) phytase). Triplicate groups of 50 fish per tank were fed dietary treatments for eight weeks. Phytase addition increased the apparent digestibilities of dry matter, protein, and P; final body weight; specific growth rate; body crude ash; body crude protein; body P and Ca contents; and vertebral P and Ca contents; but decreased the fecal P content and feed conversion ratio. However, organic acid did not affect these parameters. Both dietary phytase and organic acid significantly reduced the blood reactive oxygen species (ROS) level, serum superoxide dismutase (SOD) activity, and catalase (CAT) activity. The addition of 4 g kg− 1 organic acid to the diet supplemented with 1000 IU kg− 1 phytase caused a significant interaction on the increments of blood ROS content and serum SOD and CAT activities, which indicated increasing oxidative stress (P < 0.05). Phytase and organic acid showed no significant interaction on growth performance, body composition, and utilization of efficiency of plant-protein-source P in juvenile yellow catfish (P > 0.05).