Supplementation of Protein Hydrolysates to a Low‐fishmeal Diet Improves Growth and Health Status of Juvenile Olive Flounder, Paralichthys olivaceus

Abstract

An 11-wk feeding trial was conducted to evaluate three different protein hydrolysates as feed ingredients in high-plant-protein diets for juvenile olive flounder. Five experimental diets were fed to juvenile olive flounder to examine the effect of three different protein hydrolysates on growth performance, innate immunity, and disease resistance against bacterial infection. A basal fishmeal (FM)-based diet was regarded as a high-FM diet (HFM) and a diet containing soy protein concentrate (SPC) as a substitute for 50% FM protein was considered as a low-FM diet (LFM). Three other diets contained three different sources of protein hydrolysates, including shrimp, tilapia, and krill hydrolysates (designated as SH, TH, and KH), replacing 12% of FM protein. All diets were formulated to be isonitrogenous and isocaloric. Triplicate groups of fish (15.1 ± 0.1 g) were handfed one of the diets to apparent satiation twice daily for 11 wk and subsequently challenged against Edwardsiella tarda. Growth performance and feed utilization of fish fed hydrolysate-supplemented diets were significantly improved compared to those of fish fed the LFM diet. Dietary inclusion of the protein hydrolysates significantly enhanced apparent digestibility of dry matter and protein of the diets. In the proximal intestine, histological alterations were observed in the fish fed the LFM diet. The fish fed the hydrolysate diets showed significantly longer mucosal fold and enterocytes and greater number of goblet cells compared to fish fed the LFM diet. Respiratory burst activity was significantly higher in fish fed the TH and KH diets than fish fed the LFM diet. Significantly higher immunoglobulin levels were found in fish fed SH and KH diets compared to those of fish fed the LFM diet. Dietary inclusion of the protein hydrolysates in SPC-based diets exhibited the highest lysozyme activity. Significantly higher superoxide activity was observed in groups of fish fed the KH diet. Fish offered the protein hydrolysates were more resistant to bacterial infection caused by E. tarda. The results of this study suggest that the tested protein hydrolysates can be used as potential dietary supplements to improve growth performance and health status of juvenile olive flounder when they were fed a LFM diet. KEYWORDSEdwardsiella tarda, growth performance, intestinal morphology, olive flounder, protein hydrolysate, soy protein concentrate 1 Correspondence to: kjlee@jejunu.ac.kr

Dietary tuna hydrolysate modulates growth performance, immune response, intestinal morphology and resistance to Streptococcus iniae in juvenile barramundi, Lates calcarifer

“…In this study, tuna hydrolysate (TH) derived from processing by-products was tested in juvenile barramundi and it was found inclusion levels of 5 to 10% enhanced the FBW and SGR. Similar positive growth responses to dietary inclusion of fish hydrolysates have been found in many fish species including olive flounder, Paralichthys olivaceus 19 , yellow croaker, Pseudosciaena crocea 30 and Atlantic salmon, Salmo salar 29 . The improved growth performance in the present study following moderate levels of hydrolysate inclusion may be a result of the improved availability and subsequent uptake of free amino acids and suitable peptide fractions produced during the enzymatic process which may be beneficial for the growth performance of fish 31 .…”

“…Likewise, Khosravi et al . 19 found that the addition of protein hydrolysates in low FM diets did not alter most of the hematological indices in juvenile olive flounder, Paralichthys olivaceus while some of the health parameters (lysozyme activity, total immunoglobulin) were improved in hydrolysate supplemented groups. In the current study, the concentration of blood glucose was significantly lower in juvenile barramundi fed with 10 to 20% TH included diets compared to those in the control.…”

“…Presently, several FPHs are effectively used in aqua-feeds for their versatile properties 19 – 21 however, no information has been reported on the use of FPH in diets for barramundi. In an effort to diversify the use of FPH in aquaculture, the aim of our study was to investigate whether tuna hydrolysate (TH) is beneficial in terms of growth and immune functions for juvenile barramundi.…”

Growth Performance, Digestive Enzymes, and TOR Signaling Pathway of Litopenaeus vannamei Are Not Significantly Affected by Dietary Protein Hydrolysates in Practical Conditions

“…In recent years, studies on the effects of protein hydrolysates on aquatic animals have been reported ( Zheng et al, 2013 ; Khosravi et al, 2017 ; Quinto et al, 2018 ). The main sources of protein hydrolysates include two main categories: those obtained from plants and those obtained from animals.…”

Evaluation of shrimp or tilapia protein hydrolysate at graded dosages in low fish meal diet for olive flounder (Paralichthys olivaceus)

“…Similarly, fermented plant‐based protein concentrate was ineffective at replacing 30% FM in olive flounder diets (Seong et al., 2018). Therefore, in recent studies, incorporations of fishery side streams or protein hydrolysates were evaluated in LFM diets of olive flounder and successful results were observed (Khosravi et al., 2018; Oncul et al., 2018).…”