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® 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.