Fish waste to sustainable additives: Fish protein hydrolysates alleviate intestinal dysbiosis and muscle atrophy induced by poultry by-product meal in Lates calcarifer juvenile.

Valorising waste from the processing of fishery and aquaculture products into functional additives, and subsequent use in aquafeed as supplements could be a novel approach to promoting sustainability in the aquaculture industry. The present study supplemented 10% of various fish protein hydrolysates (FPHs), obtained from the hydrolysis of kingfish (KH), carp (CH) and tuna (TH) waste, with 90% of poultry by-product meal (PBM) protein to replace fishmeal (FM) completely from the barramundi diet. At the end of the trial, intestinal mucosal barriers damage, quantified by villus area (VA), lamina propria area (LPA), LPA ratio, villus length (VL), villus width (VW), and neutral mucin (NM) in barramundi fed a PBM-based diet was repaired when PBM was supplemented with various FPHs (p < 0.05, 0.01, and 0.001). PBM-TH diet further improved these barrier functions in the intestine of fish (p < 0.05 and 0.001). Similarly, FPHs supplementation suppressed PBM-induced intestinal inflammation by controlling the expression of inflammatory cytokines (tnf-α and il-10; p < 0.05 and 0.001) and a mucin-relevant production gene (i-mucin c; p < 0.001). The 16S rRNA data showed that a PBM-based diet resulted in dysbiosis of intestinal bacteria, supported by a lower abundance of microbial diversity (p < 0.001) aligned with a prevalence of Photobacterium. PBM-FPHs restored intestine homeostasis by enhancing microbial diversity compared to those fed a PBM diet (p < 0.001). PBM-TH improved the diversity (p < 0.001) further by elevating the Firmicutes phylum and the Ruminococcus, Faecalibacterium, and Bacteroides genera. Muscle atrophy, evaluated by fiber density, hyperplasia and hypertrophy and associated genes (igf-1, myf5, and myog), occurred in barramundi fed PBM diet but was repaired after supplementation of FPHs with the PBM (p < 0.05, 0.01, and 0.001). Similarly, creatine kinase, calcium, phosphorous, and haptoglobin were impacted by PBM-based diet (p < 0.05) but were restored in barramundi fed FPHs supplemented diets (p < 0.05 and 0.01). Hence, using circular economy principles, functional FPHs could be recovered from the fish waste applied in aquafeed formulations and could prevent PBM-induced intestinal dysbiosis and muscular atrophy. GRAPHICAL ABSTRACT.

The ameliorative effects of various fish protein hydrolysates in poultry by-product meal based diets on muscle quality, serum biochemistry and immunity in juvenile barramundi, Lates calcarifer.

In an effort to reduce the use of fishmeal (FM), the effect of using protein from poultry by product meal (PBM) along with the supplementation of three different fish protein hydrolysate (FPH) including yellowtail kingfish, carp and tuna hydrolysate (designated as KH, CH and TH, respectively) were evaluated in juvenile barramundi for growth performance, fillet quality, mucosal immunity, serum biochemistry, immune response and infection against Vibrio harveyi. Fish were fed a FM based control diet + three isonitrogenous and isolipidic diets containing 90% of PBM protein supplemented with different types of hydrolysates: 90% PBM +10% KH (90PBM + KH), 90% PBM + 10% CH (90PBM + CH) and 90% PBM + 10% TH (90PBM + TH). Growth performance and indices were unaffected by the hydrolysate supplemented diets when compared to the control. FPH supplemented PBM diets resulted in improved muscle quality by improving poly unsaturated fatty acids (PUFA), ∑n-3, ∑n-6 and ∑n-9, and health related lipid indexes were not affected. The internal architecture of spleen and kidney were not altered by test diets whilst FPH supplemented PBM modulated acidic mucins in intestine and skin of fish. Improved infection rate in response to two weeks post infection with V. harveyi in the FPH supplemented diets was further associated with an increased serum immune response and a concomitant regulation of proinflammatory and inflammatory cytokines in the head kidney. Serum biochemistry including alanine transaminase (ALT), glutamate dehydrogenase (GLDH) and total bilirubin (TB) showed a decreasing trend both in pre-challenge and post-challenge barramundi fed FPH supplemented diets whereas cholesterol level decreased significantly in post-challenge groups fed 90PBM + KH and 90PBM + TH than pre-challenge barramundi. This study signifies that supplementation of 10% with different three FPH, hydrolysed by an alcalase® enzyme in PBM-based diets for barramundi could be good strategies to overcome the negative consequences triggered by animal by-product ingredients.

Bioprocessed poultry by-product meals on growth, gut health and fatty acid synthesis of juvenile barramundi, Lates calcarifer (Bloch).

Poultry by-product meal (PBM) has been utilised as a substitute of fishmeal (FM) in many aquaculture species. However, little information is known regarding the use of bioprocessed PBM (BPBM) in aquaculture production. This study was undertaken to investigate whether replacing FM with BPBM improved growth performance, gut morphology and fatty acid synthesis of juvenile barramundi, Lates calcarifer. The PBM was bioprocessed by baker yeast, Saccharomyces cerevisae and Lactobacillus casei. The BPBM was used to replace FM at 75% and 100% (75BPBM and 100BPBM) contrasting against unprocessed PBM (75PBM and 100PBM) at the same levels and FM based diets as the control. Juvenile barramundi with a mean initial weight of 3.78±0.16 g were stocked at a density of 20 fish per tank. After the 42 days of study, the final weight, specific growth rate and feed conversion ratios of fish fed 75PBM and 75BPBM were not significantly different from the control. However, 100% supplementation diets of 100PBM and 100BPBM resulted in reduced performance in all growth and feed variables except total feed intake and survival. The hind gut microvillus density was significantly higher (P<0.05) in fish fed 75BPBM, whereas the microvillus diameter remained unaffected with the other experimental diets when compared to the control. A reduction in eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids of fish muscles led to a lower Σn-3/Σn-6 ratio in all dietary groups when compared to the control. The percentage of Σn-3 PUFAs decreased in 100% FM replacement diets of 100PBM and 100BPBM, while Σn-6 PUFAs increased when both bioprocessed and unprocessed PBM protein was increased in the diets. Fish fed bioprocessed diets had higher fatty acid hypocholesterolemic/hypercholesterolemic ratios (HH), indicating improved suitability for human consumption.

Beneficial effects of tuna hydrolysate in poultry by-product meal diets on growth, immune response, intestinal health and disease resistance to Vibrio harveyi in juvenile barramundi, Lates calcarifer.

This study was conducted to investigate the effects that tuna hydrolysate (TH) supplementation in poultry by-product meal (PBM) diets would have on growth, immunity and resistance to Vibrio harveyi infection in juvenile barramundi, Lates calcarifer. Five isonitrogenous and isocaloric diets containing fishmeal (FM) without TH supplementation (control) and four diets with 10% TH supplementation viz. a FM protein diet (FMBD + TH), a 75% PBM protein diet (LPBM + TH) and two 90% PBM protein diets, either bioprocessed (BPBM + TH) or unprocessed (HPBM + TH), were formulated for juvenile barramundi, Lates calcarifer. The diets were fed to triplicate groups of juvenile barramundi (average pool weight 12.63 ±â€¯0.11 g) for 10 weeks. Significantly (P < 0.05) higher final body weights and specific growth rates were noted in fish fed with FMBD + TH and BPBM + TH diets when compared to the control. Transmission electron microscopy observation of fish distal intestines revealed a significant enhancement of microvilli length in fish fed FMBD + TH and BPBM + TH whereas scanning electron microscopy analysis found no significant difference in microvilli density. A bacterial challenge with Vibrio harveyi was conducted for 14 days after the growth trial to test the immune response and survival of barramundi. In the pre-challenge condition, a significant reduction in blood glucose was found in BPBM + TH compared to the control, and fish in the post-challenge at 24 h had higher glucose levels compared to fish in the pre- and post-challenge conditions at 72 h. The serum lysozyme activity was significantly higher in FMBD + TH and BPBM + TH compared to the control and fish at 72 h post-challenge exhibited higher lysozyme activity in each treatment compared to all dietary groups in the post-challenge condition at 24 h and to HPBM + TH and BPBM + TH in the pre-challenge condition. Fish fed FMBD + TH, LPBM + TH and BPBM + TH diets had significantly higher survival to the bacterial challenge than fish in the control and HPBM + TH. These results showed that PBM supplemented with TH could successfully replace FM without compromising growth, however, bioprocessed PBM supplemented with TH (BPBM + TH) may significantly improve growth performance, immune response, intestinal health and disease resistance in juvenile barramundi.