The effects of concurrent supplementation of dietary phytase, citric acid and vitamin D3 on growth and mineral utilization in juvenile yellow catfish Pelteobagrus fulvidraco

This experiment was conducted to evaluate the combined effects of phytase, citric acid and vitamin D-3 on the digestibility coefficients, growth performance, body composition, and vertebral and serum mineral contents in juvenile yellow catfish (Pelteobagrus fulvidraco). The study used 1200 juvenile yellow catfish in a completely randomized design with a 2 x 2 x 2 factorial arrangement (0 and 500 IU phytase kg(-1) feed, 0 and 2 g citric acid kg(-1) feed, and 2000 and 4000 IU vitamin D-3 kg(-1) feed). Triplicate groups of 50 fish with an initial single body weight of 3 g +/- 0.0 g per tank were fed to satiety for eight weeks. 500 IU phytase kg(-1) feed addition significantly increased (P < 0.05) the apparent digestibilities of dry matter and phosphorous (P), whole body sodium (Na), P, calcium (Ca), magnesium (Mg) and zinc (Zn) retention, and vertebral P, Ca and Zn deposition. However, phytase did not enhance the growth response of juvenile yellow catfish. The addition of 2 g citric acid kg- 1 feed significantly increased (P < 0.05) weight gain (WG) and specific growth rate (SGR), and significantly decreased (P < 0.05) feed conversion ratio (FCR). High levels of vitamin D-3 significantly increased (P < 0.05) whole body Na, K, P, Ca, Mg and Zn retention while no difference in vertebral mineral deposition, the apparent digestibility of dry matter, P and protein, or growth performance between low and high levels of vitamin D-3 supplementation was observed. In addition, no significant interactions were observed among or between phytase, citric acid and vitamin D-3 on the growth or mineral utilization of juvenile yellow catfish. (C) 2014 Elsevier B.V. All rights reserved.