The influence of a dietary lipid source on growth, muscle fatty acid composition and erythrocyte osmotic fragility of hybrid tilapia

An 8-week feeding trial was conducted to determine the effects of various dietary lipids on the growth, tissue proximate composition, muscle fatty acid composition and erythrocyte osmotic fragility of red hybrid tilapia, Oreochromis sp. Five isonitrogenous and isoenergetic semipurified diets were supplemented with 10% of either cod liver oil (CLO), sunflower oil (SFO), crude palm oil (CPO), crude palm kernel oil (CPKO), or a combination of 5% CLO with 5% palm fatty acid distillates (PFAD), respectively. There were no significant effects (P > 0.05) of diet on growth but fish fed the CLO diet showed a significantly (P< 0.05) poorer feed efficiency ratio compared to fish fed the CPO diet. Lipid deposition in fish muscle was mostly similar among fish fed the various diets but bone ash was significantly higher in fish fed the CPO and CPKO diets. Muscle lipids of fish fed palm oil-based diets did not increase in saturated fatty acids content but showed significantly lower polyunsaturated fatty acid (PUFA) concentrations compared to fish fed the CLO diet. The concentrations of individual PUFA in muscle lipids were strongly influenced by dietary PUFA concentrations. Dietary lipids did not markedly affect the structural integrity of erythrocyte membranes but the erythrocytes of tilapia fed the CPO diet were slightly more resistant to osmotic lysis. It was concluded that palm oil products, especially CPO, could be successfully used in the diet of hybrid tilapia based on its availability, cheaper costs and its potential ability to enhance oxidative stability due to its low PUFA content and high natural concentrations of antioxidants.     

Dietary short-chain organic acids enhanced resistance to bacterial infection and hepatopancreatic structural integrity of the giant freshwater prawn,Macrobrachium rosenbergii

International Aquatic Research - The use of short-chain organic acids in the diets of aquacultured animals as a prophylactic to bacterial pathogens is receiving increasing research and commercial...     

Effects of Dietary Probiotics on the Growth and Feeding Efficiency of Red Hybrid Tilapia,Oreochromis sp., and Subsequent Resistance to Streptococcus agalactiae

An eight-week trial was performed to evaluate three commercial/prototype probiotics supplemented in red hybrid tilapia, Oreochromis sp. diets. Triplicate groups of tilapia were measured for growth performance, feeding efficiencies, and whole-body composition. After the feeding trial, duplicate groups of tilapia were assessed for their resistance to Streptococcus agalactiae over 23 days. Six diets were supplemented with 0.1% or 0.3% PB₁ consisting of Bacillus subtilis, 0.1% or 0.3% PB₂ consisting of B. licheniformis or 0.1% MPB consisting of Bacillus sp. and Pediococcus sp. Probiotics had no effect (p > 0.05) on growth or feeding efficiencies, although whole-body crude protein was significantly higher in the PB₁ 0.3% treatment. Tilapia in the probiotic treatments had a higher resistance to S. agalactiae and, with the exception of the PB₂ 0.1% diet, were all significantly higher than the control treatment. Although the tested probiotics were not growth promoters, dietary B. subtilis was the most effective prophylactic against pathogenic bacteria.     

Deposition of tocopherol and tocotrienol in the tissues of red hybrid tilapia, Oreochromis sp., fed vitamin E-free diets supplemented with different plant oils

Vitamin E, a potent antioxidant consisting of four isomers each (α, β, γ, δ) of tocopherol (T) and tocotrienol (T3), is found naturally in plant oils at different concentrations. In this study, four semi-purified isonitrogenous and isolipidic (10 %) diets containing canola oil, cold-pressed soybean oil, wheat germ oil, or palm fatty acid distillates (PFAD) as the sole vitamin E source were fed to triplicate groups of red hybrid tilapia (Oreochromis sp.) fingerlings (14.82 ± 0.05 g) for 45 days. Vitamin E concentrations and composition were measured in the muscle, liver, skin, and adipose tissue. Deposition of α-T (53.4–93.1 % of total vitamin E) predominated over deposition of other isomers, except in the liver of fish fed the SBO diet, where α-T and γ-T deposition was in the ratio 40:60. T3 deposition (2.6–29.4 %) was only detected in tissues of fish fed the PFAD diet; adipose tissue was the major storage depot. Fish fed the SBO diet contained significantly more (P < 0.05) muscle thiobarbituric acid-reactive substances. Muscle fatty acid composition reflected dietary fatty acid profile. This is the first study to compare the deposition in fish tissues of the naturally occurring vitamin E isomers present in plant oils. The type and concentration of endogenous vitamin E and the fatty acid composition of plant oils can affect the oxidative stability of tilapia tissues.     

Assessing the efficacy of three methionine sources in low protein and low fish meal diet for Chinese soft-shelled turtle, <Emphasis Type="Italic">Pelodiscus sinensis</Emphasis>

An 8-week feeding trial was conducted to evaluate the effects of three dietary methionine (Met) sources [dl-Met, coated-Met, and a methionine hydroxy analogue calcium salt (MHA-Ca)] for Chinese soft-shelled turtle (Pelodiscus sinensis). Triplicate groups of juvenile turtles (initial weight 3.48 ± 0.03 g) were fed twice per day at 3% of body weight with positive control diet (T1, 46% protein and 46% fish meal, FM), negative control diet (T2, 43% protein and 23% FM), or three other test diets supplemented with either 0.2% coated-Met (T3), 0.125% MHA-Ca (T4), or 0.1% dl-Met (T5) to the T2 basal formulation, respectively. The feeding trial was conducted in 15 350-L plastic containers with three replicates per dietary treatment. The results showed that the highest and lowest percentage weight gain (1023.5 ± 18.2 versus 882.1 ± 14.5%) and feed efficiency (87.2 ± 0.94 versus 81.4 ± 0.4%) were observed in turtles fed the T1 and T2 diet (P < 0.05), respectively. Significant improvement in weight gain was observed in turtles fed diets with Met supplementation, irrespective of source, compared with turtles fed the T2 diet. It was observed that dietary MHA-Ca had similar efficacy compared with dl-Met in terms of growth performance and feed utilization efficiency of the turtles (P > 0.05). Protein utilization efficiency was significantly higher in turtles fed T4 or T5 diet compared to the T2 diet. Whole body protein content (17.0 to 17.4% on a wet weight basis) in turtles fed with Met-added diets was comparable to those of turtles fed the T1 diet which were significantly higher compared to T2-fed turtles. Antioxidant defense system enzymes, superoxide dismutase, and glutathione peroxidase showed the highest activity, 658.8 ± 17.9 U/mL and 642.8 ± 17.5 μmol/L, respectively, in the serum of turtle fed the MHA-Ca supplemented diet and was significantly higher compared to turtles fed the T2 or T3 diet. The present results showed that P. sinensis are able to effectively use added MHA-Ca and dl-Met in low protein and low FM diets to enhance growth, feed utilization efficiency, nitrogen retention, and antioxidant defense system enzyme activities.     

Effects of feeding rate on growth, feed utilizationand body composition of a tropical bagrid catfish

A 10 week experiment was conducted to determine theeffects of feeding rate on growth, feed utilizationand body composition of the tropical bagrid catfish,Mystus nemurus. Catfish fingerlings with anaverage initial body weight of 12 g were fed apractical diet (36.2% protein, 16.5 kJ/g diet) atrates of 1, 2, 2.5, 3, 3.5, 4 or 5% of their bodyweight (BW) per day in two equal meals. Watertemperature was approximately 29 °C throughoutthe experiment. Percent weight gain increased almostlinearly with increasing feeding rates up to 2.5%BW/day beyond which no significant (P > 0.05)improvement in weight gain was observed. The specificgrowth rate of catfish fed rations of 1% BW/day was0.72%/day and this increased significantly to anaverage of 1.39%/day for catfish fed 2.5% BW/day andbeyond. Feed utilization did not differ significantly(P > 0.05) between fish fed 1.0 to 2.5%BW/day but decreased when rations were increased to3.0% BW/day and above. Feed efficiency ratio was0.79 for catfish fed 1.0% BW/day compared to a ratioof 0.27 for fish fed at 5% BW/day. Catfish fed 1.0%BW/day had the lowest condition factor, hepato- andviscerosomatic indices, but the highest carcass tobody weight ratio. These fish also had lowerproportions of whole body dry matter, lipid andprotein, carcass dry matter and lipid, and visceraldry matter and lipid than fish in other groups. Therewere no significant differences in either conditionindices or relative body composition of fish fedrations of 2.0 to 5.0% BW/day. Based on the growth,feed efficiency and body composition data obtained, afeeding rate of 2.5% BW per day is recommended forM. nemurus fingerlings raised at 29 °C.     

Performance of genetically improved Nile tilapia compared with red hybrid tilapia fed diets containing two protein levels

A 10‐week feeding trial was conducted to investigate the interaction between tilapia genotype and dietary protein level on the growth, feed utilization efficiency and body composition of Nile tilapia [Oreochromis niloticus L., F₉ generation of genetically improved farmed tilapia (GIFT) strain] and red hybrid tilapia (Oreochromis sp.). Two isoenergetic diets (15.5 kJ g⁻¹ diet) containing 25% or 35% crude protein were formulated and fed to triplicate groups of tilapia (12.8±0.2 g) at a fixed daily ration of 4% of their body weight. The growth performance of the GIFT tilapia fed 25% or 35% dietary protein was significantly higher (P<0.05) compared with red tilapia at either protein level. Increasing the dietary protein level by 10% led to a further 10% increase in the final weight of GIFT tilapia but no further increase was observed in the weight gain of red tilapia. Growth was influenced by the interaction between diet and tilapia genotype. Feed conversion ratios were 14% and 33% better in GIFT tilapia compared with red tilapia fed the 25% or 35% protein diet respectively. Protein efficiency ratio and net protein utilization were influenced by both diet and tilapia genotype, but not the interaction between the two. The apparent digestibility coefficients of dry matter and protein did not differ significantly between the two diets and tilapia genotypes but lipid digestibility was 1.2–4.7% higher for the GIFT tilapia. Tilapia whole‐body protein content was significantly influenced by both diet and tilapia genotype. The higher growth potential, better feed utilization efficiency and higher body protein content of GIFT tilapia compared with red tilapia should have a positive impact on tilapia farming in terms of production costs.     

Nutritive value of palm kernel meal pretreated with enzyme or fermented with Trichoderma koningii (Oudemans) as a dietary ingredient for red hybrid tilapia (Oreochromis sp.)

The aim of this study was to evaluate whether pretreatment of palm kernel meal (PKM) with a commercial feed enzyme (Allzyme Vegpro?) or solid‐state fermentation of PKM with the cellulolytic fungus Trichoderma koningii (Oudemans) could improve the nutritive value of raw PKM in the diets of red hybrid tilapia, Oreochromis sp. Seven isonitrogenous (30% crude protein) and isoenergetic (15.1 kJ g^?1) practical diets were formulated and fed close to apparent satiation to triplicate groups of 14 fish (mean initial weight 5.1 ± 0.1 g) for 10 weeks. The diets consisted of a control diet which did not contain any PKM, raw PKM diets, enzyme‐treated PKM (EPKM) or fermented PKM (FPKM) diets at 20% and 40% (dry weight basis) inclusion rates. The growth performance and feed utilization efficiency of tilapia fed 20% PKM or 20% EPKM were not significantly different (P > 0.05) from those of fish fed the control diet. Fish fed diets containing 40% EPKM showed significantly higher growth and feed utilization efficiency than fish fed 40% raw PKM owing to the improved dry matter, protein, lipid and energy digestibility of the enzyme‐treated PKM diets. The apparent protein and lipid digestibility of the 20% EPKM and 40% EPKM diets were not significantly different, and nor was the growth and feed utilization efficiency of fish fed these two diets. Hybrid tilapia fed FPKM‐based diets at all dietary inclusions tested showed the poorest growth, and this might indicate the presence of antinutrients in the resultant fungal biomass. In conclusion, it is anticipated that, with further optimization of enzyme pretreatment of PKM, higher levels of PKM could be included in the diets of hybrid tilapia, thereby reducing the impact of rising costs to feed tilapia.     

Effects of dietary organic acids on growth, nutrient digestibility and gut microflora of red hybrid tilapia, Oreochromis sp., and subsequent survival during a challenge test with Streptococcus agalactiae

A 14-week feeding trial was conducted to determine the effects of dietary organic acids. The experimental diets were added with 0, 1, 2 or 3 g kg⁻¹ of a novel organic acid blend or with 2 g kg⁻¹ of potassium diformate and fed to triplicate groups of red hybrid tilapia ( Oreochromis sp.). Upon completion, tilapia were challenged by immersion with Streptococcus agalactiae . There was no significant difference ( P >0.05) in the growth, feed utilization and nutrient digestibility among treatment groups despite a trend towards improved results with fish fed organic acid-supplemented diets. Diet pH decreased, causing a reduction in the digesta pH of the stomach and gut. Total bacteria per gram of faeces were significantly ( P <0.05) reduced from 1.81 × 10⁸ colony-forming units (CFU) (control group) up to 0.67 × 10⁸ CFU in the fish fed organic acid diets. A similar trend was observed for adherent gut bacteria. Cumulative mortality of fish fed no organic acids was higher compared with fish fed organic acid-supplemented diets at 16 days post challenge. The data showed that dietary organic acids can exert strong anti-microbial effects and have the potential to exert beneficial effects on growth, nutrient utilization and disease resistance in tilapia.