A novel enzymatic pre-treatment improves amino acid utilization in feather meal fed to rainbow trout (Oncorhynchus mykiss)

A growth trial followed by a digestibility trial were conducted to assess the bioavailability of arginine (Arg) and amino acid digestibility of two feather meals (FeMs) and their pre-treated counterparts (PTFeMs). Two FeMs, identified as FeM1 and FeM2, were incubated in 200% distilled water (%FeM w/w), with 0.05% of Savinase (R) 16L (%FeM v/w) and 2% sodium sulphite (%FeM w/w) at 55oC for 24 hr in a shaking incubator to produce PTFeM1 and PTFeM2 respectively. A basal diet, highly deficient in Arg (12.0 g/kg Arg) was formulated and 10 other diets were formulated to contain 13.5 or 15.0 g/kg Arg by adding increasing amounts of L-Arg, FeMs or PTFeMs. The experimental diets were fed for 8 weeks using a standard protocol. At 13.5 g/kg Arg, the PTFeMs supported 10.5% to 11.5% higher growth rates (p < 0.05) than their untreated counterparts. The diets formulated with PTFeMs presented 3.5%-4.5% and 2.7%-5.9% higher (p < 0.05) apparent digestibility coefficients of protein when compared to the diets containing the FeM counterparts at 13.5 and 15.0 g/kg Arg respectively. The results from this study demonstrate the potential of the pre-treatment to improve the nutritive value of FeMs in rainbow trout.