Hydrolysed Feather Meal Inclusion in Low Fishmeal Diets for Whiteleg Shrimp (Penaeus vannamei)

The global transition toward low-fishmeal formulations has intensified the search for sustainable and digestible protein alternatives in shrimp aquaculture. Enzymatically hydrolysed feather meal (HFM) represents a promising high-protein ingredient with enhanced digestibility and bioactive potential. This study evaluated the effects of graded HFM inclusion (0%-5%) on growth performance, digestive enzyme activity, antioxidant status, and muscle composition of Penaeus vannamei juveniles. Five isonitrogenous (40.2 +/- 1.9% crude protein) and isolipidic (12.3 +/- 1.4% crude lipids) diets were formulated with 0%, 1.25%, 2.5%, 3.75%, and 5.0% HFM, replacing part of the soybean meal while maintaining a constant fishmeal inclusion (6%). A total of 100 shrimp (initial weight 1.2 +/- 0.1 g; initial length 4.3 +/- 0.3 cm) were randomly distributed into 20 tanks (4 tanks per diet; 20 shrimp per diet) and reared for 50 days under controlled clear-water conditions. Growth performance, feed efficiency, digestive and antioxidant enzyme activities, and abdominal muscle composition were analysed using one-way ANOVA and polynomial regressions. Growth and feed conversion ratio were unaffected by HFM inclusion (p > 0.05). Lipase, cellulase, and carbohydrate-digesting enzymes remained stable, while trypsin and chymotrypsin showed a mild increase at 1.25%-2.5% inclusion. Glutathione peroxidase activity tended to increase (p = 0.10), whereas reduced glutathione was significantly lower in all HFM-fed groups (p < 0.001). Lipid peroxidation (TBARS) and glutathione reductase remained unchanged. Muscle protein and moisture were unaffected, while ether extract showed a modest but significant increase (p < 0.001). In conclusion, enzymatically HFM can be safely incorporated up to 5% in low-fishmeal diets for P. vannamei without impairing growth, digestive function, antioxidant defence, or flesh composition, supporting its potential as a sustainable ingredient for modern shrimp feeds.