Enhancement of shrimp Litopenaeus vannamei diets based on terrestrial protein sources via the inclusion of tuna by-product protein hydrolysates

Approximately 52–54% of the total weight of tuna fish is discarded as waste during canning. This waste can be stabilized through lactic acid fermentation to form a partially hydrolyzed, protein-rich product that is enriched with microbial biomass. The product can be used as an additive to improve the nutritional value of the terrestrial protein ingredients that are included in shrimp feed formulations. The objective of this research was to study the capacity of tuna by-product protein hydrolysates (TBPH) to improve the quality and digestibility of Pacific white shrimp (Litopenaeus vannamei) diets that contain porcine meat meal (PMM). The six experimental diets were isonitrogenous (43% crude protein) and isoenergetic (18.4 MJ kg− 1): the first contained PMM as the main protein source; four diets containing 2.5, 5.0, 7.5 or 10.0% TBPH as one of the protein dietary sources. The sixth was supplemented with 10% commercial tuna by-product meal (TBM). The diets were tested for 6 weeks in triplicate tanks, each with 10 juvenile shrimp (initial body weight of 1.6 g). There were no significant differences in total feed intake among treatments, but the shrimp fed diets supplemented with 5% TBPH had significantly greater weight gain (8.6 g), a better feed conversion ratio (1.3), and a higher specific growth rate (5.1% day− 1) than those fed diets with greater amounts of TBPH or the basal diet (one-way ANOVA tests). A broken line model revealed maximum growth of the shrimp fed 4.4% TBPH. The increased performance was attributed to the positive effect of TBPH, which provided additional attractants and improved the overall protein digestibility and amino acid profile of the diets. Thus, TBPH provided a significant nutritional benefit that positively affected the growth performance of shrimp.