Hydrolyzed feather meal as a partial fishmeal replacement in diets for European seabass (Dicentrarchus labrax) juveniles

The effects of replacing fishmeal by increasing levels of hydrolyzed feather meal (HF) on the nutrient utilization, growth performance and muscle fatty acid composition of European seabass (Dicentrarchus labrax) juveniles were evaluated. The humoral non-specific immune parameters were also evaluated in plasma. A growth trial was conducted for 18 weeks, using a practical feed formulation with 32% fishmeal and no HF added, as control (FM). Three experimental diets were formulated with the inclusion of 5 (HF5), 7.5 (HF7.5) and 12.5% HF (HF12.5), leading to a replacement of about 28, 55 and 76% fishmeal compared to the FM diet. The protein apparent digestibility coefficient (ADC) was lowest in the HF12.5 diet and was associated with higher nitrogen fecal losses, but N gain was similar among diets. Phosphorus ADC was significantly improved with the dietary incorporation of HF, decreasing fecal P losses into the environment. Fish fed the diets containing HF grew as well as those fed the FM diet. The feed intake, feed conversion ratio and protein efficiency ratio were statistically similar among dietary treatments. The protein and lipid whole body composition, as well as the muscle long-chain omega-3 fatty acid profile, remained unaffected by the fishmeal replacement. The immunological parameters assessed (lysozyme, peroxidase and ACH50) were not affected by the HF inclusion. The present study shows that an inclusion of up to 12.5% HF (76% fishmeal replacement) is possible in European seabass without impairing feed intake, growth, immune response or EPA and DHA levels in the muscle. Although energy and protein apparent digestibility coefficients (ADC) were lowest in the HF12.5 diet, energy and nutrient gain remained similar among dietary treatments. Altogether results suggest that HF is an interesting ingredient to be used in practical feed formulations for this species.