Effect of Heat Treatment at Different Stages of Rigor on the Quality of Pacific White Shrimp (Litopenaeus vannamei)

Effect of blanching and cooking on the quality of Pacific white shrimp with skeletal muscle severed (by beheading and peeling) at different stages of rigor was evaluated. Peeling and beheading shrimp in post-rigor stage resulted in higher yields compared to shrimp in in-rigor and pre-rigor stages. Weight loss due to blanching/cooking was highest when skeletal muscle was severed in in-rigor stage followed by post- and pre-rigor stages. Highest crude and sarcoplasmic protein contents were found in the shrimp blanched or cooked while in in-rigor stage followed by pre-rigor and post-rigor stages. Hardness, springiness, and chewiness were found to be better in the shrimp blanched in pre-rigor stage. Highest sensory scores for color, appearance, succulence, and odor were found for shrimp blanched or cooked in pre-rigor followed by in-rigor stage. Instrumental analysis of color and texture confirmed the sensory scores.     

Optimization of Lipid Extraction and Determination of Fatty Acid Compositions in Edible Meats of Freshwater and Marine Shrimps

Response surface methodology was applied to determine optimal conditions for lipid extraction from shrimp. Box-Behnken Design including independent variables such as extraction time, extraction temperature, and ratio of mixed solvents was used. The optimal conditions for lipids extraction were the use of petroleum ether:ethyl acetate (2.3:1, v/v) with 62 min of extraction at 52ºC. Under the optimal conditions, the extraction yields of lipids from Euphausia superba, Penaeuschinesis, Macrobranchium nipponense, and M. rosenbergii were 4.39, 2.80, 2.98, and 3.30%, respectively. Gas chromatographic analysis showed that M. rosenbergii presented the highest level of polyunsaturated fatty acid (PUFA) (48.28%) among the shrimps studied. In addition, the 20:5n3 (EPA) + 22:6n3 (DHA) value (26.43%) was second only to E. superba (31.27%). The finding suggests that M. rosenbergii is a potential PUFA source for food supplementation.     

Utilization of sorghum distillers dried grains in extruded and steam pelleted shrimp diets

Use of distillers dried grain with solubles from sorghum (sDDGS) was studied with respect to processing and physicochemical quality of shrimp feed, followed by growth trials with Litopenaeus vannamei (Pacific white shrimp). Shrimp diets with 0%, 10%, 20%, 30% and 40% sDDGS inclusion, as a replacement for soybean meal, were produced using extrusion and steam pelleting. Bulk density of extruded feed (0.53–0.58 g cm^?3) was lower than that of pelleted feed (0.61–0.65 g cm^?3), although sDDGS level did not have an impact. Finished diets were 100% sinking, with some exceptions in the case of extruded feed. Pellet durability index (89.4–96.3%) had an increasing trend up to 20% and 30% sDDGS for extruded and pelleted diets respectively. Extruded feed had higher degree of gelatinization than pelleted feed, although proportion of gelatinized starch generally decreased with sDDGS level. Water stability (76.2–91.6%) was higher for extruded feed as compared to pelleted feed, and remained unchanged or decreased with sDDGS level. The extruded and pelleted diets were evaluated in two growth trials with L. vannamei for duration of 9 and 6 weeks in 40 and 60 tanks (initial weight 0.36–0.38 g; 10 shrimps per tank) respectively. Significant differences were not observed in final mean weight and survival with respect to sDDGS level, indicating that up to 40% of this novel protein source can be used in feed formulations without affecting the performance of L. vannamei. Comparison of extruded feed with pelleted feed for impact on mean weight and feed conversion ratio did not yield conclusive results.     

Water quality and phytoplankton stability in response to application frequency of bioaugmentation agent in shrimp ponds

Splitting the recommended weekly dosage of bioaugmentation agent and applied at varying frequencies were tested to determine its effects on water quality and phytoplankton stability in tiger shrimp (Penaeus monodon) grow-out ponds. The supplier's recommended weekly dosage was followed but at varying application frequencies namely: once per week, twice per week, and four times per week for the duration of 120 culture days. A treatment with no bioaugmentation was added as control. Results showed that ammonia and particulate organic matter levels were significantly lower and plankton die-off was greatly minimized if the product was applied four times a week application compared with twice a week and weekly applications. Significant reduction in the number of luminous Vibrio species was observed in ponds with more frequent applications than those with less. For shrimp, survival and production were significantly higher in ponds with twice and four times per week applications compared to the weekly application and the control (P < 0.05). Results of this study indicate that splitting the weekly dosage of bioaugmentation agent and applying it four times per week is highly beneficial and ideal for shrimp culture.     

白斑综合征病毒卵黄抗体对凡纳滨对虾免疫相关酶活力和抗病毒能力的影响

摘要：免疫活性物质可以调动或激活虾类自身的免疫系统,提高动物的免疫机能,增强动物的抗病毒能力。有关卵黄抗体对对虾体内酶活力及抗病毒能力的影响,国内外尚未见报道。本实验通过连续投喂的方法,用3个水平(1%、0.5%、0.1%)的Ig-Guard(shrimp)制成的试验饲料,同时以基础饲料为空白对照饲喂凡纳滨对虾(Litopenaeus vannamei) 20 d,分别测定了第5,10,15,20 d血淋巴的酚氧化酶(PO)、溶菌酶(UL)、酸性磷酸酶(ACP)及肌肉匀浆液的超氧化物歧化酶(SOD)等非特异性免疫因子活性,并对血清及肌肉匀浆液中蛋白进行定量。结果表明,免疫组的PO、UL、ACP、SOD活力均显著高于对照组(P<0.05)。免疫20 d后,用白斑综合征病毒(WSSV)投喂感染。攻毒后第7 d各免疫组的相对免疫保护率分别为17.95%、23.08%、35.90%。实验结果说明,Ig-Guard(shrimp)能有效提高对虾免疫因子的活性,对于提高抗WSSV感染能力也有一定作用。将对虾免疫因子活性和累计死亡率协同分析,摄食低浓度Ig-Guard(shrimp)组较之高浓度组的酶活力高,其累计死亡率低,故笔者建议适当地投喂低浓度Ig-Guard(shrimp)更为合理。     

酶法回收虾头和虾壳中的蛋白质

利用蛋白酶水解虾壳和虾头,以水解度(DH%)和TCA可溶性氮为指标并结合感观评价,研究了各种条件对水解效果的影响。通过比较不同蛋白酶的水解效果,发现碱性蛋白酶的水解效果最好,最适的水解条件为:碱性蛋白酶添加量4IU/g,自然pH值,水解温度60℃,水解时间5～7h,固液比1∶10,风味蛋白酶(添加量13～65IU/g),于水解2h后加入,在此条件下,水解度达到20.7%,TCA可溶性氮达到42.0mg/mL,水解液无苦味和腥味,风味良好。     

镉致鸡胚胫骨软骨发育不良的研究

为了研究镉对鸡胚胫骨软骨发育的影响,选取体重相近的SPF鸡胚120枚随机分为4组,每组30枚,孵化6 d后在鸡胚气室打孔,其中对照组向卵黄囊注射PBS50μL,其他3组分别向卵黄囊注射0.05、0.1和0.2 mg/mL醋酸镉50 μL,处理10d,通过石蜡切片HE染色、阿利新蓝染色观察胫骨软骨发育情况;扫描电镜观察软...     

Extensive shrimp farming,mangrove clearance and marine fisheries in the southern provinces of Vietnam

Within the last decade shrimp farming in the Mekong Delta of Vietnam has increased by 3500%. Shrimp farming became un-sustainable in the early 1990's due to the un-planned development of this industry and the resulting self pollution of the farms, the destruction of mangrove forest and the outbreak of viral diseases. Historical data on fisheries, fishing effort and mangrove coverage were obtained from the province Minh Hai (lately divided in Ca Mau and Bac Lieu). Analysis of catch and effort data of marine fisheries in the Mekong Delta indicated a severe danger of over-exploitation of fish stocks and further decline can be expected if fisheries management only considers the demand for fish. The relation between the total fish catch (t/year), the mangrove area (ha), the engine capacity (HP) of the fishing fleet and the social incentive for fishing could be described with the model: Total catch=0.449*Mangrove area + 0.614 Engine capacity + 654 Social factor. One hectare of mangrove forest supports a marine catch of 450 kg/year     

Effect of different concentrations of potassium and magnesium on performance of Litopenaeus vannamei postlarvae reared in low-salinity water and a biofloc system

Effect of K⁺ and Mg²⁺ in water on the performance of Litopenaeus vannamei using bioflocs was evaluated. Control had water with K:Mg (1:4.57) and other treatments (K:Mg of 1:5.4, 1:4.65, and 1:3.77), both with salinity of 4 g/L. Initial mean weight of shrimp was 0.08 ± 0.007 g. No difference in shrimp growth performance and survival was observed (P > 0.05) except in the control. Our results suggest that it is possible to culture postlarvae of Litopenaeus vannamei in low-salinity water with bioflocs when the water has an initial potassium concentration of 30.90 ± 8.5 mg/L and magnesium of 167.0 ± 3.9 mg/L.