Fish muscle hydrolysate obtained using largemouth bass Micropterus salmoides digestive enzymes improves largemouth bass performance in its larval stages

Abstract

The present study utilized digestives tracts from adult largemouth bass (LMB) to hydrolyze Bighead carp muscle and obtain an optimal profile of muscle protein hydrolysates that would be easily assimilated within the primitive digestive tract of larval LMB. Specifically, muscle protein source was digested for the larva using the fully developed digestive system of the same species. The objectives of this study were: 1) to develop an optimal in vitro methodology for carp muscle hydrolysis using LMB endogenous digestive enzymes, and 2) to evaluate the effect of dietary inclusion of the carp muscle protein hydrolysate on LMB growth, survival, occurrence of skeletal deformities, and whole-body free amino acid composition. The study found that the in vitro hydrolysis method using carp intact muscle and LMB digestive tracts incubated at both acid and alkaline pH (to mimic digestive process of LMB) yielded a wide range of low molecular weight fractions (peptides), as opposed to the non-hydrolyzed muscle protein or muscle treated only with acid pH or alkaline pH without enzymes from LMB digestive tracts, which were comprised of large molecular weight fractions (polypeptides above 150 kDa). Overall, the dietary inclusion of the carp muscle hydrolysate improved growth performance of larval LMB in terms of final average weight, weight gain, DGC, SGR, and body length after 21 days of feeding compared to fish that received the diet based on non-hydrolyzed carp muscle. The study also found that hydrolysate-based feed significantly reduced skeletal deformities. The positive growth performance presented by fish in the hydrolysate-fed group possibly resulted from matching the specific requirements of the larvae with respect to their digestive organ development, levels of digestive enzymes present in the gut, and nutritional requirements.

A Novel Approach in the Development of Larval Largemouth Bass Micropterus salmoides Diets Using Largemouth Bass Muscle Hydrolysates as the Protein Source

“…The hydrolysis method for this study was based on the in vitro method described by Kwasek et al [27] with some modification. Adult LMB (2-year-old males and females) were kept at 25 • C and fed to satiation (one meal).…”

“…The first diet, the intact diet, did not contain any of the LMB muscle hydrolysates and was solely based on LMB intact protein. The dietary protein in the last four diets was based on 50% intact protein and 50% LMB muscle hydrolysates [27]. Diet A contained an equal proportion of all three of the hydrolysates.…”

“…To combat this, protein hydrolysates have been suggested as an optimal protein source for larval fish [24]. The inclusion of protein hydrolysates in formulated dry diets has been tested previously and positive results on growth performance and the occurrence of skeletal deformities have been observed at dietary inclusion levels lower than 50% [17,[25][26][27]. In addition to inclusion level, the protein sources used, conditions (pH, temperature), and the enzymes utilized are all critical in successful protein hydrolysate production and utilization [28].…”

“…[29], which can significantly impact how efficiently larval fish utilize hydrolysate-based diets [28,30]. Kwasek et al [27] used Bighead carp (Hypophthalmichthys nobilis) muscle as a protein source in the diets of larval Largemouth Bass (Micropterus salmoides) (LMB). The carp muscle was hydrolyzed with the endogenous enzymes from adult LMB in vitro and its dietary inclusion improved growth performance and reduced skeletal deformities of the larval LMB [27].…”

“…Kwasek et al [27] used Bighead carp (Hypophthalmichthys nobilis) muscle as a protein source in the diets of larval Largemouth Bass (Micropterus salmoides) (LMB). The carp muscle was hydrolyzed with the endogenous enzymes from adult LMB in vitro and its dietary inclusion improved growth performance and reduced skeletal deformities of the larval LMB [27]. However, the live feed could not be fully replaced using the carp hydrolysate-based diet, possibly suggesting that the protein source used for larval LMB diets should more closely match its nutritional requirements.…”