Optimum Replacement Value of Fish Silage for Protein Source in Pacific White Shrimp Diets

Abstract

Chemical and biological evaluations were undertaken to determine nutritive value of acid fish silage (FS) as a dietary protein source in the diet of Pacific white shrimp (Litopenaeus vannamei). Proximate composition, and amino acid profile of FS were determined for chemical evaluation; amino acid profile of FS was employed to predict its nutritive value against shrimp requirements for essential amino acids (EAA). Three biological evaluations of FS were conducted: (1) the attractability of the FS diets were compared with diets containing no FS; (2) a growth trial of 60 days was performed to determine the effects of replacing protein sources in the diet with FS, on the growth performance of the shrimp; (3) shrimp from the growth trial in the second biological experiment were evaluated to determine whether or not FS in the diet resulted in enhanced immune response against Vibrio parahemolyticus. Experimental diets were prepared containing 5 levels of FS replacing the combined fish meal and Acetes meal (kept at a constant ratio of 1:3): 0% FS (control), 12.5%, 25%, 37.5% and 50% FS replacement. For results of the chemical evaluation, the computed EAAI of FS was 98.5 indicating a well-balanced profile. In the attractability test using a custom-made setup, results showed that shrimp (1-2 g) were significantly more attracted to the diet containing 50% FS replacement than any other diet; the control and the other experimental diets were statistically similar in attractability. In the growth trial experiment, shrimp (average weight =0.01g) were fed diets of the same composition as that used for the attractability test. Results showed that weight gain (WG) and specific growth rate (SGR) of the FS-supplemented groups were significantly higher than the control group; however, 25% FS group did not significantly differ from that of the 37.5% FS. Feed conversion ratio (FCR), protein efficiency ratio (PER) and survival rate did not differ significantly among experimental groups. In the V. parahemolyticus challenge test, optimum FS replacement for immune enhancement was estimated to be 24.5% FS using a broken line model. In conclusion, the findings revealed that FS could serve as a feeding stimulant at 50% FS replacement. Likewise, FS could serve as an immunostimulant against V. parahaemolyticus in L. vannamei.