Frass is the by‐product of the larval meal industry and includes larval waste, exoskeleton sheds and residual feed ingredients. Experimental frass was derived from the larvae of black solder flies ...fed distillers' dried grains with solubles and had a protein and fat content of 216 and 60 g/kg, respectively. A 10‐week study was conducted to evaluate the effect of dietary levels of frass on growth, feed utilization, and body proximate and mineral composition of channel catfish, Ictalurus punctatus. Five diets containing 0, 50, 100, 200 and 300 g frass per kg diet were fed to channel catfish (5.24 ± 0.04 g) in quadruplicate aquaria to apparent satiation twice daily. Final weight gain was significantly increased in fish fed diets containing frass at levels from 100 to 300 g/kg. Fish fed diets without frass, and with 300 g/kg frass, showed the lowest and highest feed intake, respectively. Feed and protein efficiencies, however, were significantly lower in fish fed frass at levels of 200 g/kg and higher compared to the control diet. Survival, whole‐body composition and mineral content were not affected by frass. In summary, black soldier fly larval frass has potential as a protein source or just an ingredient for enhancing palatability of catfish diets.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The antimicrobial activity and mode of action of chitosan were evaluated against Streptococcus iniae, a pathogenic Gram‐positive bacterium of fish worldwide. Cell proliferation kinetics were examined ...following exposure to varying concentrations of chitosan. The action of chitosan on S. iniae was also investigated by measuring agglutination activity, conductivity, and extracellular and intracellular bacterial adenosine triphosphate (ATP) levels. Chitosan exhibited antibacterial activity against S. iniae at concentrations of 0.1% and above and was lethal at a concentration of 0.4% and higher. The mechanism of antibacterial activity of chitosan at the inhibitory level of bacterial growth appears to hinge upon the interaction between chitosan and the oppositely charged bacterial surface. This interplay causes agglutination, which was readily observed grossly and microscopically. After interacting with the cell surface via adsorption, an efflux of intracellular ATP was documented, which suggests that chitosan disrupts the bacterial cell causing leakage of cytosolic contents and ultimately cell death. Results suggest chitosan may be worth evaluating as a natural alternative to antibiotic against S. iniae infection of fish.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
3.
Lipid and Fatty Acid Requirements of Tilapias Lim, Chhorn; Yildirim‐Aksoy, Mediha; Klesius, Phillip
North American journal of aquaculture,
April 2011, Volume:
73, Issue:
2
Journal Article
Peer reviewed
Tilapias have been shown to have a dietary requirement for linoleic (n‐6) series fatty acids (FAs; 18:2n‐6 or 20:4n‐6). The optimum dietary levels of n‐6 previously reported were 0.5% for redbelly ...tilapia Tilapia zillii and 1.0% for Nile tilapia Oreochromis niloticus. Tilapias may also have a requirement for the linolenic (n‐3) FA series (18:3n‐3, 20:5n‐3, or 22:6n‐3), but the optimum dietary requirement levels for n‐3 in various tilapia species have not been determined. The presence of high levels of either n‐6 or n‐3 may spare the requirement of the other, although n‐6 appears to have a better growth‐promoting effect than n‐3. Tilapias possess the ability to desaturate and chain elongate 18:2(n‐6) to 20:4(n‐6) and 18:3(n‐3) to 20:5(n‐3) and 22:6(n‐3). Plant oils that are rich in n‐6, n‐3, or both FA series (e.g., soybean oil, corn oil, sunflower oil, palm oil products, and linseed oil) have been reported to be good lipid sources for tilapia. Beef tallow and pork lard are poorly utilized by tilapia. However, these lipids can be used in combination with other lipid sources provided that the essential FA requirements are met. Information on the nutritional value of fish oil for tilapias is inconsistent. Some studies have shown that the nutritional value of fish oil is similar to that of plant oils, while others have reported poor performance of diets that contain fish oil. Fish oil provided good spawning performance for tilapia broodstock reared in brackish water, whereas soybean oil yielded good reproductive performance in freshwater. The sparing effect of dietary lipids on protein utilization has also been demonstrated. However, tilapias do not tolerate as high a dietary lipid level as do salmonids. A dietary lipid level of 5–12% has been suggested as optimum in diets for tilapias.
Received April 28, 2010; accepted August 9, 2010
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
An emerging pathotype of Aeromonas hydrophila (vAh) has been responsible for widespread farm losses in the US catfish industry over the last decade. While our genetic and biochemical understanding of ...vAh has been greatly enhanced in this time frame, our ability to reliably induce the disease in the laboratory has remained limited. Taking cues from observed farm conditions associated with outbreaks, here we perturbed iron scavenging dynamics and catfish feeding status. Addition of a xenosiderophore, deferoxamine mesylate (DFO), to vAh cultures prior to immersion challenge significantly increased virulence in several vAh isolates but not in a non-epidemic strain. DFO addition did not impact vAh growth dynamics or perturb iron-sensitive gene pathways, but did significantly enhance hemolysis of catfish blood. Furthermore, hours between last feeding and immersion challenge (postprandial status), was observed to be a critical determinant of catfish susceptibility. Fish with a full gastrointestinal tract had significantly lower survival than those in a fasted state, and this effect was cumulative with that of DFO-enhanced vAh virulence. Taken together, our results not only provide a more robust challenge model, they offer actionable insights into pond level host-pathogen-environmental interactions potentially underlying vAh pathogenesis.
•Growth of virulent Aeromonas hydrophila (vAh) in the presence of a siderophore dramatically heightened virulence•Siderophore addition did not impact vAh growth or perturb iron-sensitive gene pathways, but did enhance blood hemolysis•The duration between feeding and immersion challenge was found to be a critical determinant of susceptibility to vAh•Animals fed before challenge had lower survival than fasted fish which was cumulative with siderophore-enhanced virulence
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
A study was conducted to examine the effect of dietary levels of distiller's dried grains with solubles (DDGS) on growth, body composition, hematology, immune response, and resistance of channel ...catfish, Ictalurus punctatus, to Edwardsiella ictaluri challenge. Five diets containing 0, 10, 20, 30, and 40% DDGS with supplemental lysine (Diets 1-5) as partial replacements of a combination of soybean meal and cornmeal on an equal protein basis were fed to juvenile catfish (13.33 ± 0.25 g) for 12 wk. Growth performance and feed utilization efficiency were similar for fish in all treatments. Body lipid and moisture increased and decreased, respectively, in fish feed DDGS-containing diets relative to the control group. Dietary treatment had no effect on red and white blood cell counts. Hemoglobin and hematocrit were significantly higher in fish fed diets containing DDGS than in those fed the control diet. Fish fed 20-40% DDGS diets had increased serum total immunoglobulin, and those fed the 30% DDGS diet had significantly increased antibody titers 21 d following E. ictaluri challenge. Other immune variables evaluated were not affected by dietary treatments. Preliminary results on bacterial challenge showed an increased resistance against E. ictaluri in fish fed DDGS-containing diets (Diets 2-5).
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Juvenile channel catfish (14.4 g average initial weight) were fed diets supplemented with a purified nucleotide mixture for 8 weeks. The mixture consisted of five nucleotides supplied on an equal ...basis as disodium salts at combined concentrations of 0 (control), 0.1%, 0.3%, 0.9% or 2.7% of diet. Addition of nucleotides to diet produced a dose‐dependent reduction in survival of channel catfish to Edwardsiella ictaluri. Although the reasons are unclear, the high levels of nucleotides supplemented in this study may have contributed to the decrease in disease resistance, and this decrease appeared to be unrelated to the innate immune (unaffected) and specific antibody (enhanced) responses. Stress resistance increased with a corresponding amelioration of the immunosuppressive effects of the stress response on non‐specific immunity (lysozyme and bactericidal activity) as nucleotides increased in diet. Use of exogenous nucleotides as a prophylactic treatment before culture‐related stress exposure may prove beneficial by decreasing the immunosuppressive effects of stress but not in prevention of ESC.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Dietary supplementation of yeast or yeast subcomponents (YYS) as commercial preparations of β-glucan (MacroGard®; Biotec-Mackzymal, Tromsø, Norway; and Betagard A®; Aqua-In-Tech, Inc., Seattle, WA, ...USA), mannan oligosaccharide (Bio-Mostrade mark sign Aqua Grade; Alltech, Nicholasville, KY, USA), or whole-cell Saccharomyces cerevisiae (Levucell SB20®; Lallemand Animal Nutrition, Milwaukee, WI, USA) at the manufacturer's recommended levels was evaluated on the physiological performance of juvenile channel catfish, Ictalurus punctatus. Fish were fed YYS diets for 4 wk, followed by 2 wk of control diet. Fish were sampled at the end of each feeding period (4 and 6 wk) to measure hematological and immune parameters and growth and to determine the effects of dietary β-glucan on resistance to Edwardsiella ictaluri infection and to low-water stress (6 wk). Supplementation of YYS in diets did not affect growth performance, hematology, or immune function. Survival from E. ictaluri infection was from 5 to 17.5% higher in fish fed YYS diets than in the control group, but the increases were not significant. Some improvement in stress resistance was observed in YYS-fed catfish after exposure to low-water stress. Stress reduction in fish fed diets supplemented with yeast subcomponents has been reported previously, but thus far, no explanation has been proposed for this effect. The present study and the previously published research suggest that dietary YYS supplementation does not appear to improve resistance of channel catfish to E. ictaluri.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Aeromonas hydrophila is one of the most widespread bacterial pathogens affecting freshwater fish, and an emerging pathotype of A. hydrophila has severely impacted the catfish industry over the last ...decade. In this study, we evaluated the effect of treatment with kaolin (Al2Si2O5OH4), an inert clay, on A. hydrophila chemotaxis and adhesion (two important steps of the infective process) to catfish mucus and the potential use of kaolin for controlling A. hydrophila outbreaks. Chemotaxis assays revealed that kaolin clay significantly blocked the chemotaxis and adherence of A. hydrophila to catfish mucus. Kaolin treatment at a level of 0.1% led to a significant improvement in survival (66.7%) of experimentally challenged Channel Catfish Ictalurus punctatus as compared to untreated fish (28.9%). Kaolin treatment did not alter the growth of A. hydrophila, but bacterial concentrations in the upper phase of treated cultures were significantly reduced by kaolin treatment within 15 min and were significantly increased in the pellet by 45 min of treatment, indicating the rapid formation of physical complexes through adsorption followed by gravitational settling.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
•Inclusion of larval frass improves growth and protein utilization of juvenile hybrid tilapia.•Dietary larval frass, improved natural complement activity of tilapia.•Dietary larval frass appears to ...be beneficial in increasing resistance of hybrid tilapia to Flavobacterium columnare and Streptococcus iniae infections.•Larval frass appears to be a suitable ingredient for use in tilapia diets at least at levels up to 30%.
Frass, a by-product of the larval meal industry, is heterogeneous and includes larval excrement, exoskeleton sheds and residual feed ingredients along with abundant nutrients, chitin and beneficial microbes. The present study was performed to evaluate the changes in growth, feed utilization, body composition, hematology, serum chemistry, immune responses and disease resistance of hybrid tilapia, Nile x Mozambique (Oreocromis niloticus x O. mozambique) fed diets containing frass from black soldier fly larvae, Hermetia illucens. Five diets containing frass at levels of 0, 5, 10, 20, and 30% as partial replacements of a combination of soybean meal, wheat short and corn meal on an equal protein basis were fed to juvenile hybrid tilapia (2.6 ± 0.035 g) in quadruplicate aquaria to apparent satiation twice a day for the first two weeks and once daily for rest of the feeding trail. Final weight gain was significantly increased in fish fed the diet including the highest level of frass (30%). Fish fed diets containing frass (5% to 30%) had significantly higher protein efficiency than the group fed diet without frass (control diet). Feed intake and feed utilization efficiency were not significantly affected by dietary treatments. Survival during the feeding trail, whole-body composition, hematological parameters, and serum biochemistry were not affected by dietary treatment. Serum complement activity of fish fed 30% dietary frass was significantly higher than that of fish fed other treatments. Fish fed the diets containing frass showed significant dose-dependent trends in survival against both Flavobacterium columnare and Streptococcus iniae challenges. Frass from the larvae of black solder flies fed Distillers’ dried grains with solubles has potential for use as feed ingredient for improving growth of hybrid tilapia. Use of frass in tilapia diets may prove beneficial by improving innate immune components and the resistance of hybrid tilapia against bacterial infection.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Streptococcus agalactiae is a highly pathogenic bacterium of aquatic species and terrestrial animals worldwide, whereas chitin and its derivative chitosan are among the most abundant biopolymers ...found in nature, including the aquatic milieu. The present investigation focused on the capability of S. agalactiae to degrade and utilize these polymers. Growth of S. agalactiae in the presence of colloid chitin, chitosan, or N‐acetyl‐glucosamine (GlcNAc) was evaluated. Chitosanase production was measured daily over 7 days of growth period and degraded products were evaluated with thin later chorography. Chitin had no effect on the growth of S. agalactiae. Degraded chitin, however, stimulated the growth of S. agalactiae. S. agalactiae cells did not produce chitinase to degrade chitin; however, they readily utilize GlcNAc (product of degraded chitin) as sole source of carbon and nitrogen for growth. Chitosan at high concentrations had antibacterial activities against S. agalactiae, while in the presence of lower than the inhibitory level of chitosan in the medium, S. agalactiae secrets chitosanase to degrade chitosan, and utilizes it to a limited extent to benefit growth. The interaction of S. agalactiae with chitin hydrolytes and chitosan could play a role in the diverse habitat distribution and pathogenicity of S. agalactiae worldwide.
Chitosan at concentrations of 0.2% or higher, inhibits the growth of S. agalactiae. However, lower than inhibitory level of chitosan stimulates the growth of the bacterium.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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