Mediha Yildirim-Aksoy

Effects of Probiotic Diet Supplements on Disease Resistance and Immune Response of Young Nile Tilapia, Oreochromis niloticus

Abstract Probiotic microbial feed supplements are gaining wide acceptance in livestock production, and may be applicable to aquaculture production systems. In two experiments, fry of Nile tilapia, Oreochromis niloticuswere fed a basal diet supplemented with commercially-available probiotic microorganisms. Survival, growth, disease resistance, and immunological parameters were monitored for a maximum of 94 days. Bacterial populations were higher in the digestive tracts of tilapia receiving probiotic diets, and colony morphology suggested that viable probiotic bacteria persisted up to 48 hours after feeding. Survival was higher after 39–63 days in fish receiving the Bioplus probiotic, Bacillus spp. There was no difference in growth, lysozyme, total serum immunoglobulin, complement, specific anti-streptococcal antibody levels, or mortality due to Streptococcus iniae infection either before or after disease challenge. The results suggest that these commercially-available probiotic microorganisms do not provide beneficial effects in young Nile tilapia.

Lipid and Fatty Acid Requirements of Tilapias

Abstract Tilapias have been shown to have a dietary requirement for linoleic (n-6) series fatty acids (FAs; 18:2[n-6] or 20:4[n-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 (18:3[n-3], 20:5[n-3], or 22:6[n-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 utiliz...

Effects of Yeast Oligosaccharide Diet Supplements on Growth and Disease Resistance in Juvenile Nile Tilapia, Oreochromis niloticus

Commercially available yeast and yeast subcomponents consisting mainly of β-glucan or oligosaccharide feed additives were added to diets of juvenile (12–18g) Nile tilapia (Oreochromis niloticus) at rates recommended by suppliers. Three experiments were conducted following a basic protocol with varied rates of supplementation, duration of feeding, and stocking densities. Experimental diets were fed twice daily to apparent satiation for a period of two or four weeks, at the end of which feed consumption and weight gain were measured. Following the experimental feeding period, serum components, including protein and immunoglobulin concentrations, as well as lysozyme and complement activities, were measured. A disease challenge was conducted with pathogenic isolates of Streptococcus iniae or Edwardsiella tarda. Weight gains were not significantly different in fish fed the supplemented diets when compared to the control diet. There were significant differences in fed intake within individual experiments; however, this effect was not consistent in all three experiments. Overall feed efficiency was not significantly affected by diet. There were no differences in serum components of fish sampled at two or four weeks. Fish fed the experimental diets did not have lower mortality or morbidity after disease challenge compared to fish fed the control diets. Specific antibody against S. iniae or E. tarda measured by ELISA did not reveal differences in the fish surviving the challenge. We conclude that the incorporation of these commercial yeast component products into the diet of juvenile Nile tilapia at these rates and for these feeding periods had no effect on growth, serum components, antibody responses, or survival following S. iniae or E. tarda infection.

Effects of Probiotic Bacteria as Dietary Supplements on Growth and Disease Resistance in Young Channel Catfish, Ictalurus punctatus (Rafinesque)

ABSTRACT Three separate experiments were conducted to determine the beneficial effects of probiotic bacteria added commercial catfish diets. These commercial probiotics, singly and in combination, were incorporated into a commercial diet fed to juvenile channel catfish, Ictalurus punctatus (Rafinesque), in aquaria. Microbial analyses were conducted to confirm viability of the bacteria under storage conditions. Fish were fed twice daily to apparent satiation and weighed biweekly for a period of 5 to 8 weeks. After that time, representative fish were bled for serological analysis of protein, immunoglobulin, complement, and lysozyme. Disease resistance was additionally determined in the remaining fish by observing mortality after immersion challenge with pathogenic Edwardsiella ictaluri, the causative agent of enteric septicemia (ESC). Specific anti-ESC antibody was measured by ELISA after 15 days in the fish which survived challenge. The viability of the bacteria did not decline in storage at 5°C and could be recovered between 106 and 107 colony forming units per gram (CFU/g) of diet after storage for 4 weeks. No significant differences in levels of protein, immunoglobulin, complement, or lysozyme were noted between fish consuming probiotic diets or the control diet. In one feeding trial, weight gain per fish was significantly less in the fish receiving a combination of Pediococcus and Enterococcus probiotic bacteria when compared to those consuming either bacterial supplement diet alone or the control diet. We conclude that these particular commercial dietary supplements lack specific growth promoting or immune stimulating effects in juvenile channel catfish.

Effect of Buffered and Unbuffered Tricaine Methanesulfonate (MS-222) at Different Concentrations on the Stress Responses of Channel Catfish, Ictalurus punctatus Rafinesque

ABSTRACT The effects of four concentrations (0, 90,120, and 180 mg/L) of the anesthetic tricaine methanesulfonate (MS-222) (buffered and unbuffered with sodium bicarbonate) were evaluated on anesthetization efficacy and stress responses of juvenile channel catfish, Ictalurus punctatus Rafinesque. Buffered MS-222 treatments were neutralized with sodium bicarbonate to bring the pH of exposure water to that of rearing water (pH ∼7.0). Fish were exposed to MS-222 treatments for 10 minutes after reaching stage 3 anesthetization, or for 10 minutes only for the control treatment (0 mg/L MS-222). Blood was sampled from fish at the end of the 10 minute exposure period and after 30,60,120,240, and 480 minutes recovery in aquaria to measure blood glucose and plasma cortisol and osmolality. With increasing MS-222 concentration, there were significant decreases in pH (7.0 to 5.7) and increases in osmolality (40 to 63 mOsm/kg) in unbuffered water, while osmolality (43 to 69 mOsm/kg), but not pH, were significantly different among the treatments in buffered water. As expected, anesthesia induction time was reduced and recovery time was increased as MS-222 exposure concentration increased. Buffering of exposure water had no effect on anesthetization induction or recovery. Sampling time and MS-222 concentration, but not buffering or pH, had significant effects on the stress responses. Although anesthetization reduced the cortisol response to handling, plasma cortisol concentrations increased with increasing MS-222 concentration regardless of buffering, suggesting an anesthesia effect that was unrelated to MS-222 acidification of exposure water. The blood glucose response also increased with increasing MS-222 concentration; however, glucose concentrations, unlike cortisol, were lowest in handled, non-anesthetized fish, which suggests that stress-related hyperglycemia may not be solely under cortisol control. We determined 90 mg/L MS-222 to be an effective dose for fingerling channel catfish, which provided a moderate rate of anesthesia without significantly exacerbating the cortisol response to handling.

Pond demonstration of production diets using high levels of distiller's dried grains with solubles with or without lysine supplementation for channel catfish.

Abstract Due to the increased availability and potential price advantage of distillers dried grains with solubles (DDGS), there is considerable interest in utilizing this product in aquaculture diets. The response of channel catfish Ictalurus punctatus to practical diets containing 20% and 30% DDGS with and without lysine supplementation was evaluated over a 150-d pond trial. Twenty earthen ponds were stocked with 650 juvenile channel catfish. The basal diet contained 35% soybean meal, 15% cottonseed meal, and 23.7% corn meal and was based on a typical practical diet formulation for channel catfish. The experimental diets, which were formulated to contain 32% protein and 6% lipid, were as follows: diet 1 (control [basal] diet) contained 0% DDGS and 0% lysine; diet 2 included 20% DDGS and 0% lysine; diet 3 contained 20% DDGS and 0.10% lysine; diet 4 contained 30% DDGS and 0% lysine; and diet 5 included 30% DDGS and 0.20% lysine. There were no significant differences in the measured variables (i.e., final ...

Examining the interplay between Streptococcus agalactiae, the biopolymer chitin and its derivative

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.

The effects of dietary inclusion of a Saccharomyces cerevisiae fermentation product in a commercial catfish ration on growth, immune readiness, and columnaris disease susceptibility

ABSTRACT We evaluated a Saccharomyces cerevisiae fermentation product (Diamond V Original XPC) in hybrid catfish (Ictalurus furcatus x I. punctatus) for its potential effects on growth, blood parameters, and disease resistance. The trial featured four levels of inclusion that were added to a commercial 32% protein floating catfish ration. Following six weeks of feeding, we observed marginally heightened resistance to columnaris disease and saw significant changes in the levels of immune effectors in the serum, including lysozyme, complement, and immunoglobulin.