Abstract
This study investigated the effects of tuna hydrolysate (TH) inclusion in fishmeal (FM) based diets on the growth performance, innate immune response, intestinal health and resistance to Streptococcus iniae infection in juvenile barramundi, Lates calcarifer. Five isonitrogenous and isoenergetic experimental diets were prepared with TH, replacing FM at levels of 0% (control) 5%, 10%, 15% and 20%, and fed fish to apparent satiation three times daily for 8 weeks. The results showed that fish fed diets containing 5% and 10% TH had significantly higher final body weight and specific growth rate than the control. A significant reduction in blood glucose was found in fish fed 10%, 15% and 20% TH compared to those in the control whereas none of the other measured blood and serum indices were influenced by TH inclusion. Histological observation revealed a significant enhancement in goblet cell numbers in distal intestine of fish fed 5 to 10% TH in the diet. Moreover, fish fed 10% TH exhibited the highest resistance against Streptococcus iniae infection during a bacterial challenge trial. These findings therefore demonstrate that the replacement of 5 to 10% FM with TH improves growth, immune response, intestinal health and disease resistance in juvenile barramundi.
Highlights
Lates calcarifer, a euryhaline carnivorous fish species commonly known as barramundi or Asian sea bass, is widely cultured throughout the Indo-Pacific region and Australia[1,2]
Fish protein hydrolysates (FPH) derived from raw waste materials produced through enzymatic hydrolysis are regarded as promising aqua-feed ingredients due to their favorable functional[22,23,24] and nutritional properties[25,26]
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 final body weight (FBW) and specific growth rate (SGR)
Summary
A euryhaline carnivorous fish species commonly known as barramundi or Asian sea bass, is widely cultured throughout the Indo-Pacific region and Australia[1,2]. The effects of dietary FPH have been evaluated in many commercially important fish species as a partial replacement or supplement to fishmeal[7,12,13], as immunostimulants to defend against stress and pathogens[7,14,15] and as attractants to increase diet palatability[16]. The findings of these studies suggest that dietary inclusion of FPH at an appropriate level can have beneficial effects on the feed intake, digestibility, growth performance, innate immunity and specific disease resistance of fish. 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
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