Physicochemical Properties of Pepsin-Solubilized Collagen Extracted from Nile Tilapia (Oreochromis niloticus) Scale

ABSTRACT

The aim was to investigate the physicochemical properties of pepsin-solubilized collagen (PSC) extracted from fish scales of Nile tilapia. The results indicated that Nile tilapia scales are rich in collagen. Therefore, the scales are a promising cost-effective collagen source. The conversion of hydroxyproline to collagen was 12.9. Based on the patterns of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), PSC comprised at least two different α chains, α1 and α2, and was classified to be type I with no disulfide. Fourier transform infrared spectroscopy spectrum showed that the bands of amide A, I, and II of PSC were found at 3,301, 1,631, and 1,239 cm^?1 wavelength. The content of imino acids was 187 residues per 1,000 total amino acid residues. Maximum solubility was observed at pH 4, and minimum was at pH 7. Almost no change in solubility was observed in the presence of NaCl up to 2% (w/v), and the decrease was more pronounced with increasing NaCl concentration. The temperature of denaturation was 35.4°C. Results show that PSC has physicochemical properties that can be applied in the cosmetics, biomedical, pharmaceutical, and food industries.     

Fillet Yields from Four Strains of Nile Tilapia (Oreochromis niloticus) and a Red Variety

Tilapia (Oreochromis, spp.) have been introduced globally and domesticated, resulting in a number of different strains. This diversity offers the potential for difference in body morphology and, in turn, fillet yields. A trial was conducted at Auburn University, Auburn, Alabama, to compare processing characteristics of four populations of Oreochromis niloticus using two domesticated strains (Egypt and Ivory Coast), two less domesticated strains (Sagana and Lake Victoria), and a red variety (Santa Fe). Male tilapia (N?=?25/strain) were manually processed and the dress-out percentage and visceral fat calculated. Mean individual weights of pre-processed fish were similar (range = 403.8 ± 27.6 g to 413.8 ± 24.5 g) with the exception of the larger Sagana strain (434.2 ± 15.4 g). The Ivory Coast strain had the highest percent dress out (33.1% ± 2.1%), while the Sagana strain had the lowest (29.6% ± 1.5%). The Red strain had the greatest percent visceral fat (2.3% ± 1.0%) and the Sagana had the lowest (0.2% ± 0.4%).     

Optimization of Phosphorus Fertilizer in Supplemental Feed‐Fed Based Nile Tilapia (Oreochromis niloticus) Ponds

An experiment was conducted in earthen ponds at the Asian Institute of Technology, Thailand to determine different phosphorus fertilizer dose effects on Nile tilapia production, water quality variables, nutrient utilization and cost‐benefit under supplemental feeding. Five phosphorus fertilization rates were used as treatments e.g. 100%, 75%, 50%, 25% and 0% of 7 kg P ha week^?1. Nitrogen fertilization rate was fixed at 28 kg N ha week^?1 for all the treatments. Sex‐reversed Nile tilapia were stocked at 3 fish m^?2, and 30% CP floating feed fed at 50% satiation feeding rate. Nutrient budget showed higher phosphorus fertilizer input resulted in higher phosphorus sink in the sediment. Mean weight, mean weight gain, daily weight gain and net yield were not significantly different among treatments (P > 0.05). Total Kjeldahl nitrogen, total phosphorus and soluble reactive phosphorus were significantly different among treatments. Economic analysis showed phosphorus fertilization resulted in positive net returns. Though the gross income was not affected by different fertilization rates, significantly lowest cost was found in the treatment using 25% phosphorus fertilizer. It can be concluded from the research that 25% phosphorus fertilization might be used as an alternative strategy of Nile tilapia pond culture in terms of economic return and nutrient loss in sediment.     

Production Economics of Nile Tilapia (Oreochromis niloticus) Pond Culture in El-Fayum Governorate,Egypt

Econometric techniques were used to estimate a production function for tilapia pond culture in El-Fayum Governorate, Egypt, utilizing cross-sectional field data. Explanatory variables were feed, initial stocking weight, and pond size. The function was used to examine returns to scale, estimate the productivity of feed and initial stocking weight, and estimate the profit maximizing demand equations for feed and fingerlings. Diminishing returns to scale seem to exist for tilapia pond culture. Optimal economic stocking and feeding rates, yield, and profits for the whole sample were estimated at prevailing prices. Results indicated that producers were using stocking rates greater than the optimal by 36% to 115% and using insufficient feed by 8% to 22%. Investigation of the effects of changes in tilapia selling price and feed price on optimal stocking and feeding rates, yield, and profits showed that a change in tilapia selling price has greater effect on profits, yield, stocking, and feeding rates than a proportional change in feed price. Profits, feeding, and stocking rates are more sensitive than yield to changes in selling price, while feeding rate is more sensitive than stocking rate, yield, and profits to changes in feed price.     

Geosmin and Off-Flavor in Nile Tilapia (Oreochromis niloticus)

Abstract

The concentration of geosmin (1,10-trans-dimethyl-trans-9-decaol) in fresh tilapia were analyzed by applying high-vacuum distillation, extraction and gas chromatography techniques. The distribution of geosmin in the fish was determined by examining tissues from various parts of tilapia, along with the rates of geosmin absorption and purging. Analysis showed that when geosmin was added to fish flesh at concentrations ranging from 2.8 to 390 μg per kg of flesh, the rate of recovery was 51 to 89%. Sensory evaluation detected muddy flavor in freshwater tilapia with geosmin content ranging from 7.55 to 9.85 μg/kg of fish flesh. However, panelists failed to detect muddy flavor in brackish water tilapia that contained geosmin only in the range of 1.5 to 2.6 μg/kg. Among various tissues of the fish, the intestines contained the highest geosmin concentration, and appeared in descending order in the abdominal, skin and muscle tissues. After holding for 2 h in water with 5 and 50 μg/l geosmin, tilapia absorbed 17.6 and 42.2 μg/kg geosmin in the flesh, respectively. Holding the fish over longer periods in water with higher geosmin content resulted in a greater amount of absorption. In contrast, transferring muddy-flavored fish to static clean water purged geosmin from the fish but it required at least 16 days to eliminate the muddy flavor.     

Dynamic Viscoelastic Properties of Tilapia (Oreochromis niloticus) Skin Gelatin

ABSTRACT

The viscoelastic properties of gelatin extracted from tilapia skin (protein yield: 21.2%) were evaluated using dynamic rheology tests. The flow curves of tilapia gelatin sols (1.0–6.6% w/w, 40°C; 0.5%, 2–40°C) complied with the Herschel-Bulkley model (R² = 0.92–0.99), indicating the presence of yield stress, while the gelling and melting temperature of gelatin dispersions (1.0–6.6%) fit well with the Eldridge-Ferry model (R² = 0.97). Tilapia skin gelatin displayed good thermo-stability and strong gel-forming properties, showing great potential as an alternative for mammal-based gelatin applied in various food products.     

吉富等品系尼罗罗非鱼的起捕率差异

在常规土质鱼池中进行了吉富“８８”、“７８”和埃及等四品系尼罗罗非鱼的起捕率比较试验。结果表明吉富品系的三网累计起捕率显著地高于其他品系（Ｐ〈０．０１）。１９９５年的试验中，吉富的三网累计起捕率为６７％、“８８”为３８％，“７８”为２３％，埃及为２２％。１９９６年的试验中，吉富的三网累计起捕率为８１．５％，“８８”为６２％，试验结果表明吉富品系尼罗罗非鱼的起捕率较高。     

不同养殖模式对尼罗罗非鱼（Oreochromis niloticus）生长、免疫性能及水质的影响

为探讨循环水养殖模式(RAS组)和池塘养殖模式(池塘组)对尼罗罗非鱼生长、免疫性能及水质影响的变化规律,开展了为期8周的养殖试验。结果表明：(1)RAS组中鱼体增重率(WGR)(597.36±169.79)显著高于池塘组(470.98±142.99)(P < 0.05),但饲料转化率(FCE)(1.17±0.02)却显著低于池塘养殖系统(1.47±0.03)(P < 0.05)。特定生长率(SGR)和肥满度(CF)也高于池塘养殖系统,但差异不显著(P > 0.05);(2)在第4周和第8周分别测定了鱼体胃和肠中消化酶活性显示,第4周时,RAS组中肠蛋白酶活性值(1387.56±278.43)显著高于池塘组(1129.99±382.67)(P < 0.05);第8周时,肠脂肪酶活性(18.11±4.28)显著高于池塘组(12.89±8.00)(P < 0.05);(3)在第4周和第8周分别测定了鱼体肝胰脏、头肾和血清中碱性磷酸酶(ALP)、溶菌酶 (LSZ)和总超氧化物歧化酶(T-SOD)活性,显示整体上RAS组免疫性能低于池塘组;(4)每周测定水体氨态氮和亚硝态氮含量显示,RAS组氨态氮维持在0.0067 ~ 0.0212 mg / L区间内,亚硝态氮含量位于0.0027 ~ 0.0087 mg / L范围内,均低于池塘组。     

Economic Analysis of Nile Tilapia (Oreochromis niloticus) Production in Tanzania

In Tanzania, Nile tilapia culture is a promising aquaculture enterprise. Information on production costs could assist fish farmers in economic and financial planning. Economic profitability of small‐scale Nile tilapia production in Tanzania is analyzed using a model that simulates individual fish growth and takes into account fish population dynamics in the pond. The results suggest that the current practiced mixed‐sex tilapia culture without predation is not economically sustainable. Extension efforts should be geared toward developing a Nile tilapia production system that is based on a hand‐sexed all‐male tilapia. Meanwhile catfish can be introduced in ponds to control overcrowding in mixed‐sex tilapia culture without predation. Studies to determine optimal pond sizes, availability of feed, and a quality fingerling supply chain are also fundamental for developing a sustainable Nile tilapia production system in Tanzania. Under improved Nile tilapia production systems, returns are high enough to justify investment through borrowed capital from formal institutions.     

Oxytetracycline-Induced Blood Disorder in Juvenile Nile Tilapia Oreochromis niloticus (Trewavas)

Abstract.— This study examined the long-term effect of a common aquaculture antibiotic, oxytetracycline, on several blood parameters of the Nile tilapia Oreochromis niloticus under laboratory conditions. The fish were fed daily on isocaloric (24.56 ± 0.96 J/mg gross energy) and isonitrogenous (38.89 ± 0.08% crude protein) diets incorporated with varying concentrations of the drug (5.00, 2.50, 1.25 and 0.63%) for 8 wk. A control diet with no oxytetracycline was fed to another group of fish. Significant reductions in leukocyte, erythrocyte, thrombocyte, hematocrit, and hemoglobin values were observed, the reductions being directly proportional to the concentrations of the drug in the diet, indicating an anemic response. Though the use of oxytetracycline in aquaculture can be beneficial, the results from this investigation suggest that the drug may have some level of interference with the blood chemistry of the fish at therapeutic dosage.     

Offspring Growth in a Diallel Crossbreeding with Three Strains of Nile Tilapia Oreochromis niloticus

Abstract— A complete diallel crossing of three strains, Stirling, Korean and Local, was used to evaluate heterosis of intraspecific crossbreeding on early growth of Nile tilapia Oreochromis niloticus . All possible F-1 hybrid offspring were obtained and their growth rates to 90 d were compared. The specific heterosis for F-1 hybrids in Stirling × Korean, Stirling × Local and Korean × Local crosses were 7.61, 5.63 and 7.70 for weight, and 0.47, 0.26 and 0.55 for length, respectively. The purebred Stirling strain showed better growth than the other two strains (P < 0.05). When growth of F-1 hybrids was compared between sexes, males grew more rapidly than females (P < 0.05). However, no differences were observed in growth of male or female between hybrid groups. Purebred males in the Stirling strain were slightly heavier than those in the Korean and Local strains, and Local × Stirling, Korean × Local and Local × Korean crosses. However, in purebred females Stirling was superior to Korean, but not the Local strain and all F-1 hybrid crosses. Implications to choose the appropriate strains for developing a breeding program of tilapia are also discussed.     

尼罗罗非鱼淀粉酶性质的初步研究

研究了尼罗罗非鱼(Oreochromis niloticus)肝脏淀粉酶的基本性质及金属离子对该鱼淀粉酶活性的影响。结果表明:罗非鱼淀粉酶活力的最适pH是6.5,最适底物浓度是2%。研究金属离子对该鱼淀粉酶活力影响,一价金属离子K+、Li+、Na+对酶活力影响较小;二价金属离子Cu2+对酶活力具有抑制作用,Zn2+对酶活力无明显影响;三价金属离子Al3+对酶活力具有抑制作用,但效果不是很强烈,Fe3+对酶活力具有明显的激活作用;碱土金属Mg2+、Ca2+对淀粉酶活性有激活作用,而Ba2+对酶具有抑制作用;重金属离子Cd2+、Pb2+有明显的抑制作用。     

Control of spawning activity in female Nile tilapia (Oreochromis niloticus) (L.) by temperature manipulation

The aim of this study was to maximize the spawning of Oreochromis niloticus females in a specific time period. Females were divided randomly into control and treatment groups. In the treatment groups, females were kept for one week at 28±0.5 °C, after which they were exposed to a reduced water temperature of 22±0.5 °C for 7, 14 and 28 days. Thereafter, the temperature was restored to 28 °C. Females in the control groups were kept continuously at a water temperature of 28 °C. All females were checked daily for signs of spawning for the duration of the experiments and were manually stripped if ready to spawn. The following parameters were calculated for period of 3 and 7 days following a 28 °C temperature restoration: spawning rate, number of eggs per female, weight of female, relative fecundity (eggs g⁻¹ body weight) and the percentage of hatched and swim-up fry. The highest spawning rate of 39.5% was obtained in the 14-day trial over a period of 7 days, while the corresponding value in the control was 12.5%. The percentages of hatched and swim-up fry in the 14- and 28-day trials, however, were significantly higher in the controls than in the corresponding treatment groups.     

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.     

A Probiotic Cocktail as a Growth Promoter in Nile Tilapia (Oreochromis niloticus)

The aim of this study was to evaluate Lactobacillus acidophilus, Streptococcus thermophilus, Bifidobacterium bifidum, and yeast Saccharomyces cerevisiae singly and in combination as probiotic supplements in Nile tilapia (Oreochromis niloticus) fingerling diets. All the probiotic-supplemented diets resulted in growth higher than the control. Best growth rate, food consumption, and food conversion (P < 0.05) were in the group fed a cocktail of the three bacteria. Feed cost, return on weight gain, and profit margin increased in fish groups fed diets inoculated with probiotics. Supplementation with Lactobacillus acidophilus, Bifidobacterium bifiduim, and the three-bacteria cocktail were most effective in eliminating mortality in an A. hydrophila challenge.     

Natural Food Selectivity Changes with Weights of Nile Tilapia,Oreochromis niloticus (Linnaeus), Reared in Fertilized Earthen Ponds

This work was carried out to study the relationship between fish weight and natural food selectivity of Nile tilapia, Oreochromis niloticus (Linnaeus) reared in earthen ponds without supplementary diet and to guide the adaptation of feeding and fertilization strategies. Fish were stocked (1.5 fish/m²) in four fertilized earthen ponds (0.1 ha) for 6 months. Fifty fish were sampled monthly to estimate individual total weight and length and evaluate stomach contents. Fish specimens were categorized into different weight classes: <25 g, 25–50 g, 50–75 g, 75–100 g, and 100–125 g. Overall, the 50–75 g weight class had the highest degree of stomach fullness. The intestinal length-fish length ratio was similar across all fish weights, ranging from 2.9–3.4. Likewise, the composition of food items found in fish stomach was ranked as phytoplankton > detritus > zooplankton. Phytoplankton contribution to gut content increased with increasing fish weight, while detritus and zooplankton contribution decreased. Zooplankton never exceeded 1% of total stomach contents. Cyanobacteria, Chlorophyceae, Bacillariophyceae and Euglenophyceae mostly represented the phytoplankton. Bacillariophyceae dominated the phytoplanktonic portion of stomach contents at small fish size (<75 g/fish), while Chlorophyceae is the dominant group at large fish size (> 75 g/fish). Fish could select Cyanobacteria and Euglenophyceae at all fish weights, meanwhile Chlorophyceae and Bacillariophyceae were eaten with slight selectivity at larger weights..     

三种生态环境下尼罗罗非鱼免疫因子的比较

随机选取海水池塘(盐度28)和淡水池塘养殖及水库天然增殖的3种不同生态环境下、体质量为200~500g的尼罗罗非鱼为研究材料,采用生物化学方法测定3种生态环境尼罗罗非鱼血清中碱性磷酸酶、酸性磷酸酶、过氧化物酶、谷胱甘肽还原酶的活性和蛋白质量浓度。结果显示,3种生态环境中罗非鱼血清中碱性磷酸酶和酸性磷酸酶活力差异不显著(P0.05),其余各组间罗非鱼血清中过氧化物酶和谷胱甘肽还原酶的活性及血清蛋白质量浓度差异显著(P0.05),酶活力和蛋白质量浓度依次为:水库海水池塘淡水池塘。试验结果表明,水库天然增殖的尼罗罗非鱼具有较高的磷酸酶活性。     

沸石强化活性污泥法在尼罗罗非鱼养殖中的应用

试验结果表明,养殖系统出水水质较进水水质有明显改善.经过100 d的循环水养殖,尼罗罗非鱼的平均体质量由30.34 g增加至120.08 g,平均生长速度为0.89 g/d,存活率为85.6%.     

土池低盐度水体河蟹生态育苗试验

2003年3~5月,在上海崇明进行了河蟹(Eriocheirsinensis)在低盐度水体的土池中育苗实验,主要技术措施包括亲本的强化培育、施肥养水、敌害生物的控制和利用、活饵料的科学使用和水质调控等。结果表明:(1)亲本强化培育可以提高其生殖性能;(2)土池育苗中各期幼体的变态时间长于工厂化育苗,因而总的出苗时间比工厂化育苗长5~7d;(3)通过综合管理措施,在低盐度(9~12)条件下河蟹土池生态育苗单产和出苗率分别为(60·18±30·17)kg/hm2和(3·12±1·55)%,总的出苗时间为(25·2±1·9)d。