Effect of macroalgae as a functional ingredient in grow-out diets on the biological performance, digestive capacity, and immune response of totoaba, Totoaba macdonaldi

Recent research evaluating functional ingredients, such as prebiotics, has resulted in a reduction of enteritis caused by some plant ingredients in carnivorous fish. Macroalgae contains polysaccharides that have the characteristics of a prebiotic ingredient. Thus, the objective of this study was to evaluate the effects of macroalgae meal inclusion in formulated Totoaba macdonaldi diets containing soybean meal. Two isoproteic (48%) and isolipidic (13%) diets were formulated to meet totoaba nutritional requirements containing 26% soybean meal, the control diet (SBM-C) without prebiotic and one with the addition of 3% Mega Smart Kelp a macroalgae meal prebiotic (SBM+Pre). In addition, 2 commercial diets formulated with SMB at two levels (7 and 14% labeled ALG1 and ALG2, respectively) and supplemented with the macroalgae meal prebiotic (1.5%) were evaluated. A total of 120 totoabas (157.83 g) were distributed into 450-L tanks in triplicate groups. At the end of the bioassay, the fish fed the SBM-C and SBM+Pre diets had significantly higher growth, better dietary protein efficiency, and higher digestibility compared to fish fed ALG1 and ALG2. Furthermore, a lower expression level of immunoglobulin M ( igm ) and interleukin ( il8 ) genes was observed in the fish fed the prebiotic experimental diets. These results revealed that the commercial diets resulted in lower productive performance of the juveniles and negatively affected the intestinal health of the totoabas, even more than the SBM-C and SBM+Pre diets that included soybean meal and is possibly related to saponin content of these diets.