The effect of substituting fishmeal with poultry by-product meal in diets forTotoaba macdonaldijuveniles

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Four diets were formulated to evaluate the partial to total substitution of fishmeal with poultry by-product meal (PBM) (0, 33, 67 and 100PBM) in diets for totoaba juveniles (Totoaba macdonaldi). Amino acid profiles from diets and fatty acid content in diets and muscle tissue were used to assess the fish performance using PBM as fishmeal replacement. Stable isotopes of nitrogen (δ15N) were measured in muscle and liver tissue to quantify the retention of each protein source. At the end of the experimental period, the fish fed the 67PBM diet had a significantly higher growth gain increase compared to the other treatments (almost 2000% over an 86 days period; TGC of 1.06). The total replacement of fishmeal with PBM led to low growth gain increase (ca. 220% over 72 days; TGC of 0.52) and increased mortality. Both fish performance and tissues' fatty acid composition suggest that the 100PBM diet was deficient in essential fatty acids. An isotope-mixing model applied to isotope ratios of muscle and liver tissues of fish fed the 67PBM tissues indicated that PBM was retained into muscle and liver tissue in a higher proportion than its level of inclusion in the diet. We conclude that PBM is a good source of nutrients for totoaba juveniles when used in up to 67% fishmeal replacement level in diets containing 52% protein leading to adequate growth rate and survival.