Use of alternative plant and animal protein blends, in place of fishmeal, in diets for juvenile totoaba, Totoaba macdonaldi

The present study evaluated the replacement of fishmeal (FM) by blends of alternative protein sources in diets for juvenile (8.0 +/- 0.5 g) Totoaba macdonaldi. Using a FM-based control diet containing 53% crude protein and 13% crude fat, a 3 x 3 factorial experiment was conducted replacing FM, at levels of 33, 66 and 100% by weight, with three blends of the test ingredients, as follows: 1) Arthrospira meal blend: 70% Arthrospira sp. meal, 15% blood meal, 15% soy protein concentrate (SPC); 2) blood meal blend: 70% blood meal, 15% Arthrospira sp. meal, 15% SPC; and 3) SPC blend: 70% SPC, 15% blood meal, 15% Arthrospira sp. meal. At the end of the 6-week feeding trial, significant effects of the alternative protein blends were detected, in which fish fed the Arthrospira meal and SPC blends had significantly (P < .05) better performance than fish fed the blood meal blend across all growth parameters (percent weight gain and thermal growth coefficient) and feed utilization indices (feed efficiency and protein efficiency ratio). Also, fish fed the former two blends deposited more crude protein and fat in whole body and muscle tissues, concurring with the growth response observed. However, the effects of protein blend on body condition indices (hepatosomatic index, condition factor, and muscle ratio) and on the concentrations of trypsin and chymotrypsin in anterior intestine and pyloric caeca, did not depict clear trends. A correspondence between levels of dietary amino acids (AA) in blends and accumulated AA in muscle, was not observed. However, significant effects of the level of FM replacement were also detected, in which the responses in growth, feed utilization, most body condition indices, and proximate composition of fish whole body, deteriorated as the level of FM replaced increased. All things considered, results indicate that the Arthrospira meal and SPC blends, but not the blood meal blend, can be used to replace at least 33% FM in the diet for totoaba, without adversely affecting growth and survival. The possible reasons for the decreased performance of fish fed the blood meal blend, or when fed any of the blends at levels higher than 33%, are discussed.