Nutritional Evaluation of Fish feeds Formulated with Fish discards or Shellfish waste as Alternative Protein Sources

Abstract

In the present study, nutritional profiling of the alternative main protein sources (AMPs) such as shellfish waste, fish offal and by-catch were carried out to evaluate the possible role to replace the fishmeal in the diet. Five diets were prepared with 40% (by weight) dried filtrate of autolyzed prawn and crab wastes (Diet A), dried fish offal (Diet B), dried by-catch (Diet C), a mixture of dried offal and shellfish waste (1:1 w/w, Diet D) and the reference diet (Diet E) using a commercial fish meal (CFM) as main protein sources. Other ingredients were common to all diets. Proximate composition of CFM, AMPs and five prepared diets were determined. Micronutrient contents, namely, total amino acid content, free amino acids, and fatty acid composition of the prepared diets were also analysed. The nutrient content of AMP was different only in the fish offal, of which the crude protein content (56.96±1.78) was significantly lower than that of the autolysed shellfish waste (71.75±5.38), dried by-catch (65.26±1.63) and CFM (70.06±1.257) (ANOVA, Tukey test, p<0.05). Crude lipid content of fish offal (22.81±0.57) was the highest while that was significantly different from each other (5.26±1.12, 13.55±1.61 and 18.46±0.735 for shellfish waste, dried bycatch, and CFM respectively (ANOVA, Tukey test, p<0.05). Mean crude protein of Diet B and C were significantly lower than that of other three diets. Crude fat, n-6 fatty acids and polyunsaturated fatty acids of four test diets were comparable to those of the reference diet while essential amino acids and n-3 fatty acids were significantly higher in reference diet. Presence of free amino acids in Diets A, C and D is an added quality to use the AMPs in formulating aqua feed. Economically viable feed can be prepared by using AMPs compared to the fishmeal diet and it confirms the possibility to replace fishmeal in formulated fish feed. Feeding trials will confirm the feed palatability, digestibility and growth performances of fish.