Effects of Marine Protein Hydrolysates as Squid-Liver Powder Replacements on Growth Performance, Digestive Capacity and Health Status of Pacific White Shrimp (Litopenaeus vannamei)

This study investigated the replacement of squid-liver powder (SLP) with different marine protein hydrolysates in diets for Pacific white shrimp (Litopenaeus vannamei) over an eight-week feeding period. A control diet contained 5% SLP, whereas four test diets replaced 1% of the diet (dry-matter basis) with tuna hydrolysate liquid (TH), shrimp hydrolysate powder (SH), fish hydrolysate powder (FH), or salmon silage liquid (SS), with soybean meal adjusted to maintain dietary protein balance. Shrimp fed the TH diet showed higher final body weight (15.76 ± 0.24 g shrimp−1) and specific growth rate (3.18 ± 0.02% day−1) than those fed the other experimental diets (p < 0.05). TH also increased feed intake (20.96 ± 0.49 g shrimp−1) and was associated with higher trypsin activity (3236 ± 226 unit h−1 mg protein−1) and improved protein digestibility. Histological observations indicated greater hepatopancreatic cell density and increased intestinal villus height in the TH group. In addition, survival of shrimp fed TH (90.0 ± 2.8%) was higher than that observed in the FH and SS groups (p < 0.05), and hemolymph from TH-fed shrimp showed stronger inhibitory activity against Vibrio parahaemolyticus. Overall, among the evaluated hydrolysates, 1% tuna hydrolysate (dry-matter basis) produced the most consistent improvements across growth performance, digestive capacity, and selected health-related indicators, supporting its feasibility as a partial substitute for squid liver powder in shrimp diets.