Abstract In the present study, we evaluated the effects of the hydrolysis of phytate of defatted rice bran (DRB) by a pretreatment with non-commercial phytase produced by Saccharomyces cerevisiae (DRB-PS) compared to the application of Natuphos® (commercial phytase produced by the BASF Company) (DRB-PN) in diets for grass carp, Ctenopharyngodon idella. Fish (57.55 ± 0.4 g) fed one of the experimental diets in triplicates for 35 days. Effects of the phytase used on blood parameters, intestinal proteases and hepatic glucose were not observed (p > 0.05). Similarly, no differences were found for serum phosphorus (P). However, were found higher levels of calcium (9 and 5.25%) in the control treatment in relation to DRB-PS and DRB-PN respectively, besides higher calcium-phosphorus ratio was found in this treatment. For the fish carcass composition was not statistically different (p > 0.05) except total lipids, which showed its highest content in fish fed on the DRB-PN diet (p < 0.05). The obtained results suggested that the use of the phytase, irrespective to its source may eliminate the use of traditional P sources in fish diets.

ABSTRACT The purpose of this study was to develop and improve protein concentration techniques for two industrial by-products with the potential for use in fish feed. In particular, we chemically characterized crambe meal and sunflower meal and their protein concentrates. Three different protein concentration methods were tested: isoelectric pH (pHi), acid pH and alkaline pH. For crambe and sunflower meals extraction using the pHi method was most efficient in terms of protein yield and crude protein content in the concentrates; this method also increased lysine and methionine content in the concentrates. The water holding capacity of the sunflower protein concentrate was greater than that of the crambe protein concentrate. The crambe protein concentrate had a foam-formation capacity of 15%, which stabilized at 6% after 90 minutes. The protein concentration method also reduced total phenolic content by approximately 50% in the concentrates compared with the meals. Therefore, we conclude that protein concentration using the pHi method is the most efficient technique for crambe and sunflower meals, and the use of this technique can decrease total phenolic compounds while improving meal quality for fish feeding.