3种投喂模式对中华绒螯蟹性腺发育和生化组成的影响

2015年4—10月在江苏常州金坛市指前镇芦家村省级高效设施渔业示范点6口面积0.667hm~2试验塘(编号1~6#)中,投放中华绒螯蟹和日本沼虾苗种,密度分别为2.25×10~4只/hm~2和150kg/hm~2,分别投喂配合饲料、冰鲜杂鱼和饲料与冰鲜杂鱼混合,每种投喂模式设两个重复,定期测定肝胰腺指数、性腺指数、出肉率、总可食率和体成分的生化组成。试验结果显示,在体质量接近的条件下,3种投喂模式对成蟹的性腺指数和肝胰腺指数无显著影响(P0.05),9月杂鱼组雌雄个体的性腺指数和肝胰腺指数略低于配合饲料组和混合投喂组,而混合投喂组的性腺指数略高于其他两组。不同投喂模式对各组织中华绒螯蟹的干质量中生化组成影响较小,仅杂鱼组雌蟹肝胰腺中脂肪含量为71.44%,显著低于饲料组(86.94%)和混合组(87.67%)(P0.05)。不同投喂模式对各组中华绒螯蟹组织湿质量中生化组成无显著影响(P0.05)。综上,用投喂配合饲料替代杂鱼投喂成蟹,可以提高雌蟹肝胰腺中的脂肪含量,而对性腺发育和生化组成无不利影响。     

磷脂和HUFA对中华绒螯蟹幼蟹存活、生长、蜕壳及生化组成的影响

实验用中华绒螯蟹(Eriocheir sinensis)幼蟹初始体质量为1.8 g左右。饲料A添加6%鳕鱼肝油和4%大豆卵鳞脂(饲料含4.53%磷脂和1.08%HUFA), 饲料B添加10%的猪油(饲料含0.39%磷脂和0.18%HUFA); 实验蟹单个体饲养(可防止蜕壳期间蟹相互残杀而获得饲料外的营养源), 雌蟹(F)、雄蟹(M)各60个, 实验周期120 d。结果表明: 两组饲料条件下, 幼蟹的存活率、增重率、特定生长率、平均蜕壳次数、蜕壳间隔时间及肝胰腺指数均无显著差异(P>0.05)。但无论是雌蟹还是雄蟹, A组幼蟹肝胰腺和肌肉的总脂含量显著低于B组(P<0.05), 并且A组蟹肝胰腺和肌肉中磷脂、多不饱和脂肪酸和高度不饱和脂肪酸的含量显著高于B组(P<0.05)。这表明, 在中华绒螯蟹幼蟹饲料中添加4.53%磷脂和1.08%HUFA对其存活、生长、蜕壳无显著影响, 但可使其肝胰腺和肌肉中的总脂含量降低, 而磷脂、多不饱和脂肪酸和高度不饱和脂肪酸的含量升高。本研究结果旨在为中华绒螯蟹幼蟹的营养学研究提供理论依据, 同时也为生产上幼蟹饲料的开发提供参考。     

不同水温对个体养殖系统中华绒螯蟹幼蟹摄食率的影响

为了研究不同水温条件下对中华绒螯蟹幼蟹摄食率的影响,选用“江海21”中华绒螯蟹幼蟹（7.5～14.5g/只）为试验对象,采用自动控温循环水封闭的中华绒螯蟹养殖系统,设置4个温度组,分别为10℃、16℃、22℃、28℃,每个组别设置3个平行,每个平行3个重复,试验为期140 d,试验过程记录饲料的饲喂量;结果发现温度3组的中华绒螯蟹摄食量、日均摄食量和日均摄食率极显著的高于温度1组和温度4组（P <0.01）;温度3组和温度2组的中华绒螯蟹摄食量、日均摄食量和日均摄食率存在显著差异,温度3组的显著高于温度2组（P <0.05）;说明22℃的温度饲养的华绒螯蟹摄食率最佳,其次为16℃。     

不同脂肪源饲料对中华绒螯蟹幼蟹生长、消化酶活力和脂肪酸组成的影响

选用初始体重为(2.15±0.10)g的中华绒螯蟹(Eriocheir sinensis)雄性幼蟹,随机分为5组(每组12只幼蟹),饲喂100%鱼油组(简称F1组)、100%豆油组(F2组)、100%亚麻油组(F3组)、50%鱼油+50%豆油组(F4组)、50%鱼油+50%亚麻油组(F5组)不同脂肪源配制的5种等氮等能饲料。实验蟹单个体养殖,实验周期为112 d。结果表明,F5组体重、增重率和特定生长率都显著高于其他饲料组(P0.05),各组的蜕壳间隔和肝胰腺指数没有显著差异(P0.05)。肝胰腺组织消化酶活力测定结果表明,F1组幼蟹肝胰腺的类胰蛋白酶活力显著高于其他各组(P0.05);F3组的胃蛋白酶活力显著高于其他各组(P0.05);F1组、F2组和F4组的脂肪酶活力显著高于其他两组(P0.05);各组的淀粉酶活力差异不显著(P0.05)。脂肪酸测定结果表明,肝胰腺和肌肉中的亚油酸(LOA)(C18:2n-6)、亚麻酸(LNA)(C18:3n-3)、EPA(C20:5n-3)和DHA(C22:6n-3)等主要脂肪酸含量与饲料脂肪酸组成呈正相关关系,F1组的高度不饱和脂肪酸(HUFA)含量显著高于其余各组(P0.05),F2组的LOA含量显著高于其余各组(P0.05),F3组的LNA含量显著高于其余各组(P0.05)。本研究结果表明,以50%的豆油或亚麻油替代鱼油能促进中华绒螯蟹幼蟹的生长,但可能使幼蟹的成活率降低。以豆油或亚麻油替代鱼油会影响幼蟹胰蛋白酶、胃蛋白酶和脂肪酶的活力和肝胰腺、肌肉脂肪酸组成。     

维生素C对中华绒螯蟹非特异性免疫的影响

通过在以鱼粉、豆粕、玉米粉和麦麸为主要原料配制而成的每100g基础饲料中分别添加0、250、500、1 000、1 500 mg的VC(以VC多聚磷酸酯为VC源)配制5种试验饲料,对均重为(37.52±2.19)g的中华绒螯蟹进行为期60 d的饲养试验,以酚氧化酶(PO)、抗菌力(Ua)、溶菌酶(UL)、超氧化物歧化酶(SOD)、碱性磷酸酶(AKP)和酸性磷酸酶(ACP)等指标为判据,研究VC对中华绒螯蟹体液免疫因子的影响.结果表明,VC对中华绒螯蟹各组织器官中PO、Ua、UL、SOD、AKP和ACP等活性有显著或极显著的影响(P<0.05或P<0.01),在适宜范围内,随着vc添加量的增加,PO、Ua、UL、AKP和ACP活性显著增强,从而增强中华绒螯蟹的非特异性免疫力,而SOD活性则显著降低(P<0.05),表明VC作为天然抗氧化剂在中华绒螯蟹体内发挥了很大的作用.综上所述,VC作为免疫刺激剂能有效地增强中华绒螯蟹的非特异性免疫力,且VC适宜添加量以500～1 000 mg·(100g)-1饲料为宜.     

2种饵料模式对稻田养殖中华绒螯蟹幼蟹养殖性能和生理代谢的影响

为优化稻田养殖中华绒螯蟹(Eriocheir sinensis)幼蟹的饵料模式,本研究分别采用配合饲料和传统饵料(豆粕、麸皮、玉米和小麦)投喂稻田养殖中华绒螯蟹幼蟹152 d,每种投喂组各3个重复,比较2种饵料模式对幼蟹养殖性能、蛋白质代谢、消化酶、抗氧化和免疫指标的影响。结果显示,配合饲料组的雌蟹和雄蟹体质量均高于传统饵料组,但差异不显著(P>0.05);就养殖性能而言,2种饵料模式下,配合饲料组正常幼蟹的平均体质量及产量、1龄早熟蟹平均体质量及其产量、总产量和成活率均略高于传统饵料组,饵料系数显著低于传统饵料组(P<0.05);就蛋白质代谢而言,配合饲料组雌蟹和雄蟹血淋巴中的总蛋白含量显著高于传统饵料组(P<0.05),而传统饵料组雄蟹血淋巴中的尿素氮含量和肝胰腺中的谷草转氨酶活力显著高于配合饲料组(P<0.05);配合饲料组雌蟹和雄蟹肝胰腺中的脂肪酶均显著高于传统饵料组(P<0.05),而雄蟹的α-淀粉酶活力显著低于传统饵料组;配合饲料组的雌蟹血淋巴中总抗氧化能力、碱性磷酸酶、酸性磷酸酶活力和肝胰腺中酸性磷酸酶活力均显著高于传统饵料组(P<0.05)。综上所述,投喂配合饲料可以提高稻田扣蟹的养殖性能、促进蛋白质沉积和脂类吸收、增强幼蟹抗氧化和免疫能力、提高蟹种质量。     

池养中华绒螯蟹幼蟹生长特性的初步研究

经测量和数理统计分析,确定池养条件下幼螯(中华绒螯蟹幼蟹,下同)背甲长与年龄呈直线关系,体重与年龄为幂函数关系,并计算出它们相应的回归方程式。研究结果表明,在不同饲养条件下,幼蟹生长率略有差异,并揭示出幼蟹个体生长存在着显著的差异性。在营养和溶氧相似的条件下,动蟹在适温范围内的生长与水温呈正相关。根据对185只不同时期幼蟹的测量,计算出幼蟹背甲长对体重的关系式为W=0.4209L~(3.1150)。     

三水系中华绒螯蟹幼蟹形态判别程序的建立和使用

以中华绒螯蟹幼蟹为研究对象,每只幼蟹分别测量30个形态性状参数,用聚类分析和逐步判别两种方法进行综合处理和比较分析。（1）聚类分析结果表明：长江、瓯江幼蟹形态相近,而辽河幼蟹与上述两者的形态差异较大;（2）用逐步判别筛选出的14个形态参数的判别分析表明：三个种群间的形态差异极显著（P＜0．01）,判别准确率为81．4％－88．4％（P1）和82．5％－91．4％（P2）,判别效果依次为辽河蟹＞瓯江蟹＜长江蟹,平均拟合概率为85．5％;（3）进一步用上述14个形态参数中对判分析贡献较大的9个形态参数作判别分析,构建了种群判别公式,平均拟合概率虽降至80．4％,但可减少测定和计算工作量的36％,比较实用。     

池塘养殖不同规格中华绒螯蟹扣蟹生化组成的比较研究

为探究池塘养殖不同规格扣蟹的营养状况,以长江流域池塘养殖的4种规格(体质量,A组0.3～1.0 g,B组1.0～3.5 g,C组4.0～7.0 g,D组8.0 g)扣蟹为研究对象,采用生化分析的方法,研究其肝胰腺指数(HSI)及组织常规生化组成。结果:(1)随着扣蟹规格的增大,其HSI也明显增大,且通过回归曲线得知两者大体呈幂函数关系;(2)就肝胰腺常规生化而言,无论雌蟹还是雄蟹,肝胰腺中粗脂肪及灰分的质量分数均随着扣蟹规格的增大而显著增加,粗蛋白质量分数则与之相反,表现为随着扣蟹规格的增大而显著降低(P0.05);(3)就蟹体常规生化而言,雌、雄个体中水分及粗脂肪的质量分数均随着扣蟹规格的增大而显著降低,粗蛋白质量分数则随着扣蟹规格的增大而显著增加(P0.05)。结果表明,不同规格扣蟹的HSI和常规生化组成差异显著(P0.05),其中大规格蟹种的营养状况较好,因此更适合于成蟹阶段养殖。     

豆油替代鱼油对中华绒螯蟹幼蟹生长、非特异性免疫和抗病力的影响

以酪蛋白和明胶为蛋白源配制5组等氮等能的实验饲料, 分别为全鱼油(F1)、25%(F2)、50%(F3)和75%(F4)豆油替代组和全豆油组(F5), 每组4个重复, 投喂初始体质量为(0.27±0.03) g的中华绒螯蟹(Eriocheir sinensis)幼蟹6周, 评价豆油替代鱼油的饲料对幼蟹生长、非特异性免疫力和抗病力的影响。结果发现, 各组幼蟹的存活率差异不显著(P>0.05); F4组幼蟹的增重率和特定生长率显著高于F1组(P<0.05), 但与其他各组差异不显著(P>0.05)。F4组幼蟹的血清酸性磷酸酶和碱性磷酸酶活性均显著高于其他各组(P<0.05), F5组最低。幼蟹的血清中超氧化物歧化酶活性以F4组最高, 显著高于F3组(P<0.05), F3和F4组均显著高于其他各组(P<0.05), 其他F1、F2和F5三组间差异不显著(P>0.05)。F1组幼蟹的血清丙二醛含量最高(P<0.05), 其余各组之间则差异不显著(P>0.05); F4组幼蟹的血清酚氧化酶活性最高, 而F5组最低(P<0.05); 各组幼蟹的溶菌酶差异不显著(P>0.05)。实验结束后, 采用嗜水气单胞菌(Aeromonas hydrophila)攻毒10 d, 发现F5组幼蟹最早出现死亡, 且该组幼蟹的累积死亡率显著高于F1和F4组(P<0.05)。结果提示, 采用豆油完全替代饲料中的鱼油对幼蟹的生长影响不显著, 但会降低其抵抗感染疾病的能力; 用75%豆油替代鱼油可在明显提高幼蟹免疫机能和抗病力的情况下获得良好的生长性能。

     

饵料结构对池塘河蟹生长性能及营养积累的影响

通过全程投喂冰冻小鱼、全程投喂颗粒饲料及颗粒饲料和冰鱼混合投喂的三种方式,对平均规格达(6.25±0.31)g/只,投喂280 d后,采样测定生长指标、肝胰腺指数、性腺指数。经单因素方差分析结果显示饲料组及混合组的平均规格、成活率、显著大于冰鱼组(P0.05),特定生长率在组间差异不具有统计学意义(P0.05),冰鱼组的肥满度及饵料系数远大于其他两组,且差异具有统计学意义(P0.05)。颗粒饲料组投喂下的雌、雄蟹肝胰腺指数最高,冰鱼组的雌、雄蟹性腺指数最高,由此可见,颗粒饲料组仍有生长的空间。从成本核算来看,混合组效益最高,颗粒饲料组其次,冰鱼组最小,从投入产出比来看,颗粒组最高。综上所述,全程投喂颗粒饲料对河蟹生长及营养积累有促进作用,具有更广阔的应用前景。     

Evaluation of palygorskite on pellet quality,growth, antioxidant status and mineral contents of Chinese mitten crabs (Eriocheir sinensis)

This study evaluated the palygorskite inclusion effects on the pellet quality, growth, antioxidant status and mineral contents of Chinese mitten crabs. Crabs (n = 640; initial average weight, 1.36 ± 0.02 g) were allocated into four groups with eight replicates of twenty crabs. A basal diet supplemented with 0, 10, 20 and 40 g/kg palygorskite was fed to crabs for 8 weeks respectively. Results exhibited that dietary addition of palygorskite enhanced the pellet process electrical energy consumption, improved the hardness and durability (p < .05), reduced percentage of fines and dissolved weight loss of pellets (30, 60, 120, 240, 480 min; p < .05) in the water. Crabs had no differences on the weight gain, specific growth rate, feed conversion ratio, abdominal meat ratio and edible viscera index among the groups (p > .05). Palygorskite inclusion decreased the MDA contents of edible viscera and abdominal meat (p < .05) of Chinese mitten crabs. The ether extract contents of edible viscera in palygorskite inclusion groups were lower than that of the control group (p < .05) in Chinese mitten crabs. Furthermore, palygorskite addition linearly increased the Fe level in the edible viscera and reduced tissue Pb and Cr (p < .05) accumulations of Chinese mitten crabs. In conclusion, palygorskite inclusion could improve pellet quality, enhance the antioxidant capacity and Fe content of edible viscera, decrease the edible viscera ether extract level and tissue Pb and Cr accumulations without impairing the growth performance of Chinese mitten crabs, but increased the electrical energy consumption of pelleting.     

Nutritional qualities of normal and precocious adult male Chinese mitten crabs (Eriocheir sinensis)

The nutritional values of edible gonad, hepatopancreas and muscle tissues from normal and precocious adult male Chinese mitten crabs (Eriocheir sinensis) were investigated herein. The results showed that the average weight and meat yield (MY) of normal crabs were significantly higher than those of precocious crabs, while the hepatopancreas indexes (HSI) and gonadosomatic indexes (GSI) had no significant differences. Precocious and normal crabs had greater protein and lipid contents, respectively, and the differences were mainly reflected in gonads and hepatopancreas. While assessing the amino acid profiles, both precocious and normal crabs could be high‐quality protein sources, particularly the precocious crabs which showed higher levels of essential amino acids. In fatty acid profiling experiments, precocious crabs revealed higher EPA, ∑n‐3 polyunsaturated fatty acids (PUFA) and ∑n‐3/∑n‐6 ratios than normal crabs; however, DHA and ∑n‐6 PUFA contents were considerably lower. Additionally, contents of nutritious minerals K and Ca in precocious crabs were significantly higher than those in normal crabs, while Zn and Fe were significantly lower. In short, our data indicated that precocious Chinese mitten crabs are also a nutritious food, and even in some respects their nutritional value is higher than normal crabs.     

Effects of dietary cholesterol levels on moulting performance,lipid accumulation,ecdysteroid concentration and immune enzymes activities of juvenile Chinese mitten crab Eriocheir sinensis

Effects of dietary cholesterol levels on moulting performance, lipid accumulation, ecdysteroid concentration and immune enzymes activities of juvenile Eriocheir sinensis were investigated. Crabs were fed with feeds contained various cholesterols of 1100, 2100 and 3200 mg kg^?1 in both paddy fields and laboratory experiments. In paddy fields trial, the crabs fed with diets contained 3200 mg kg^?1 cholesterol achieved higher growth rate than those fed with diets contained no supplemental cholesterol (1100 mg kg^?1). In laboratory trial, moulting frequencies of crabs fed with diets contained 3200 mg kg^?1 cholesterol were higher than those of crabs fed with diets contained no supplemental cholesterol from the 6th to 10th moult. Further laboratory experiment indicated that intermoults of crabs fed with diets contained 3200 mg kg^?1 cholesterol significantly shortened compared with crabs fed with the basal feeds (1100 mg kg^?1 cholesterol). In the intermoult, total lipid content, ecdysterone concentration and three immune enzymes in crabs were increased with the increment of dietary cholesterol levels between the 7th and the 8th moult in laboratory experiments. Taken together, dietary cholesterol not only enhanced moulting performances of growth, survival and moult frequency, but also enhanced total lipid storage, ecdysterone concentration and three immune enzymes activities in the intermoult period.     

pH胁迫对中华绒螯蟹5种非特异性免疫指标的影响

测定了不同pH(4.5,6.0,7.5,9.0,10.5)胁迫1、4、7、10d后中华绒螯蟹(Eriocheir sinensis)血细胞呼吸爆发(RP)、血细胞破碎物上清液(HLS)酚氧化酶(PO)、血清溶菌酶(LSZ)、酸性磷酸酶(ACP)及碱性磷酸酶(ALP)活性的变化.结果表明:在pH胁迫后第1天,pH4.5组...     

酵母硒对中华绒螯蟹幼蟹生长、体组成分及抗氧化能力的影响

实验饲料中以酵母硒形式分别添加硒0(对照)、0.2、0.4、0.6、0.8和1.0 mg/kg(饲料中硒总含量分别为0.11、0.23、0.43、0.66、0.87、1.09 mg/kg), 配制成6组半纯化饲料, 投喂初始体质量为(0.27±0.01) g的中华绒螯蟹(Eriocheir sinensis)幼蟹, 进行为期6周的饲养实验。结果表明, 当饲料硒的添加量为0.4 mg/kg时, 幼蟹的增重率、存活率及全蟹体粗蛋白质含量均显著高于其他各组(P<0.05)。同时, 随着饲料中硒水平的提高, 幼蟹的肝胰腺和肌肉中硒含量也相应显著升高(P<0.05)。肝胰腺和血清中的谷胱甘肽过氧化物酶活性则随着硒添加量的提高而呈现出先升高后降低的趋势, 当硒添加量为0.4 mg/kg时达到最高, 且显著高于添加量为0.8 和1.0 mg/kg的饲料组(P<0.05)。幼蟹血清和肝胰腺中丙二醛含量随着硒添加量的增加而呈现出先降低而后升高的趋势, 其中0.4 mg/kg饲料组最低, 并显著低于对照组和1.0 mg/kg饲料组(P<0.05)。硒添加量小于或等于0.6 mg/kg的各组, 其还原型谷胱甘肽含量显著低于0.8和1.0 mg/kg饲料组(P<0.05)。结果提示, 饲料中适量添加硒(0.4~0.6 mg/kg, 硒总含量为0.43~0.66 mg/kg)能促进中华绒螯蟹幼蟹的生长, 提高饲料蛋白质效率和抗氧化能力。以血清谷胱甘肽过氧化物酶活性为判据, 采用二次回归模型进行拟合发现, 当饲料中硒添加量为0.51 mg/kg (饲料中硒总含量0.59 mg/kg)时, 中华绒螯蟹幼蟹可获得最佳的生长效果, 因此建议中华绒螯蟹幼蟹饲料硒的适宜添加量为0.4~0.6 mg/kg。

     

不同规格中华绒螯蟹亲本子一代在扣蟹阶段养殖性能的比较研究

为探究中华绒螯蟹(Eriocheir sinensis)亲本规格对其子代在扣蟹阶段养殖性能的影响,本试验在相同的养殖环境下将4种规格河蟹亲本(规格I:雌90~110 g、雄140~160 g;规格Ⅱ:雌115~135 g、雄160~180 g;规格Ⅲ:雌140~160 g、雄220~240 g;规格Ⅳ:雌190~210 g、雄290~310 g)所产的大眼幼体养殖至扣蟹,并比较各组扣蟹的体质量、增重率、特定生长率、成活率及最终产量差异。试验结果显示:(1)不同规格的河蟹亲本,其子一代在大眼幼体至豆蟹阶段的平均体质量、成活率以及增重倍数均无明显差异(P>0.05);(2)在豆蟹至扣蟹养殖阶段,各组幼蟹的生长速度差异大体上与其亲本规格的差异相一致,其中Ⅰ组幼蟹在8—10月期间的平均体质量均显著低于Ⅳ组(P<0.05);(3)养殖效果方面,各组扣蟹平均规格和最终产量均随着亲本规格的提高而提高,其中Ⅳ组扣蟹的最终平均体质量显著高于Ⅰ组扣蟹(P<0.05);(4)就规格分布而言,Ⅳ组扣蟹2.00~3.99 g规格的比例显著低于另外3组,而≥6.00 g规格的比例显著高于另外3组(P<0.05)。结果表明,中华绒螯蟹亲本规格对其后代的养殖性能存在影响,大规格河蟹亲本子一代在扣蟹生产阶段生长速度快、养殖效果好,因此建议在生产上选择大规格亲本的后代用于扣蟹养殖。     

Effects of dietary folic acid on growth,antioxidant capacity,non‐specific immune response and disease resistance of juvenile Chinese mitten crab Eriocheir sinensis (Milne‐Edwards, 1853)

An 8‐week study was conducted to determine folic acid requirement and its effect on antioxidant capacity and immunity in juvenile Chinese mitten crab Eriocheir sinensis (Milne‐Edwards, 1853), followed by a challenge assay with the pathogen Aeromonas hydrophila for 2 weeks. Folic acid was added to a basal diet at seven levels (0, 0.5, 1.0, 2.0, 4.0, 8.0, 16.0 mg folic acid kg^?1 diet), and a diet free of folic acid and vitamin B₁₂ was also included as a control. Crabs were fed twice daily in 32 tanks with 7.76–8.17 mg oxygen L^?1, 25.0–31.0 °C and 7.5–8.3 pH. Growth and feed efficiency were significantly greater in crabs fed ≥2.0 mg folic acid kg^?1, but not significantly different between crabs fed diets >2.0 mg folic acid. The superoxide dismutase activity and glutathione S‐transferase activity were highest in crabs fed ≥2.0 mg folic acid kg^?1, followed by those fed 0.5 and 1.0 mg folic acid kg^?1, and the control diet. The malondialdehyde content was highest in crabs fed the control diet, followed by those fed 0 mg folic acid kg^?1, and the lowest value occurred in those fed ≥0.5 mg folic acid kg^?1. Phenoloxidase activity and total haemocytes were significantly higher in crabs fed ≥2.0 mg folic acid kg^?1 than other diets. Crabs fed 2.0 mg folic acid kg^?1 had the highest lysozyme, acid phosphatase and alkaline phosphatase activities but the lowest cumulative mortality. The optimum dietary folic acid requirement by E. sinensis was estimated at 2.29–2.90 mg kg^?1 diet.     

Effects of dietary protein level on growth,feed utilization and digestive enzyme activity of the Chinese mitten crab,Eriocheir sinensis

A feeding trial was conducted using isoenergetic practical diets to evaluate the effects of the dietary protein level on growth performance, feed utilization and digestive enzyme activity of the Chinese mitten crab, Eriocheir sinensis. Four experimental diets were formulated containing 250, 300, 350 and 400 g kg^?1 protein and 16 kJ g^?1 gross energy. Each diet was randomly assigned to triplicate groups of juvenile crab with mean initial body weight 3.56 ± 0.16 g and mean shell width 15.31 ± 0.06 mm. Juvenile crab were reared in indoor flow‐through system consisting of 12 plastic tanks (1.0 m × 0.6 m × 0.5 m) and fed diets twice daily at 6–8% of body weight for 12 weeks. Performance was judged on the basis of growth (specific growth rate of weight, SGR_G; specific growth rate of shell width, SGR_SW), feed conversion ratio (FCR) and protein efficiency ratio (PER). A decreased FCR was observed with increasing dietary protein levels. Both SGR_G and SGR_SW significantly increased with increasing dietary protein levels up to 350 g kg^?1, whereas there were no significant differences for protein levels from 350–400 g kg^?1. Application of broken line regression analysis to SGR_G provided an estimate of 347.8 g kg^?1 dietary protein for maximal growth. The highest PER was observed in crab fed the diet containing 350 g kg^?1 protein (P < 0.05). The percent survival was not affected (P > 0.05) by the different dietary treatments. No significant differences were observed in the apparent digestibility coefficients of crude lipid and dry matter among dietary treatments (P > 0.05). However, the apparent digestibility coefficients of crude protein and energy in crab fed different protein levels significantly increased with increasing dietary protein level (P < 0.05). Both amylase and protease activities in the intestine of E. sinensis were studied. The amylase activity decreased significantly (P < 0.05) with increased dietary protein level and protease activity increased. Regression analysis showed a negative effect of inclusion of dietary protein level on amylase activity (P < 0.05). However, protease activities were found to be positively correlated (P < 0.05) with dietary protein level. The protein content of the crab significantly increased with dietary protein levels up to 350 g kg^?1 (P < 0.05), but no significant differences (P > 0.05) were founded with protein levels higher than 350 g kg^?1.