UTILIZATION OF DIETS SUPPLEMENTED WITH MICROBIAL PHYTASE BY SEA-BASS (DICENTRARCHUS-LABRAX) JUVENILES

A trial was carried out to compare the growth performance, body compos ition and apparent digestibility coefficients (ADC) of diets by seabas s, with an initial weight of 13.5 g, fed diets including fish meal (68 .6 % of the dietary protein) or soybean meal (65.6 % of the dietary pr otein) as the main protein sources. Microbial phytase was added to the soybean meal based diet (1 000 and 2 000 IU . kg(-1)) and to the fish meal based diet (2 000 IU . kg(-1)) in order to study its effect on p hosphorus utilisation. Results of this trial showed that growth rate, feed conversion and nitrogen retention were significantly better in fi sh fed the fish meal based diet. Energy retention was similar in both groups. ADC of protein were similar among groups. ADC of phosphorus wa s significantly higher in the fish meal based diet (63 %) than in the soybean meal based diet (25 %). Supplementation of the fish meal based diet with microbial phytase did not improve the ADC of phosphorus, wh ile in the soybean meal based diet the inclusion of 1 000 and 2 000 IU . kg(-1) of microbial phytase significantly increased the ADC of phos phorus to 71.5 % and 79.8 %, respectively. It is concluded that for pr actical purposes supplementation of diets with microbial phytase may p rove valuable in diets including high levels of plant feedstuffs. (C) Ifremer/Elsevier, Paris.