渔业科学进展  2021, Vol. 42 Issue (5): 139-148  DOI: 10.19663/j.issn2095-9869.20200506001
0

引用本文 

钟国防, 田鑫鑫, 谢春元, 黄旭雄, 陈乃松, 黄卫, 朱站英. 芽孢杆菌有氧发酵豆粕替代鱼粉对大口黑鲈幼鱼生长性能、血清生化指标及肠组织结构的影响[J]. 渔业科学进展, 2021, 42(5): 139-148. DOI: 10.19663/j.issn2095-9869.20200506001.
ZHONG Guofang, TIAN Xinxin, XIE Chunyuan, HUANG Xuxiong, CHEN Naisong, HUANG Wei, ZHU Zhanying. Effects of Replacing Fish Meal with Bacillus Aerobically Fermented Soybean Meal on the Growth Performance, Serum Biochemical Indices and Intestinal Histology of Largemouth Bass (Micropterus salmoides)[J]. Progress in Fishery Sciences, 2021, 42(5): 139-148. DOI: 10.19663/j.issn2095-9869.20200506001.

基金项目

公益性行业(农业)岗位科学家项目:特色淡水鱼营养需求与绿色饲料开发(CARS-46-30B)资助

通讯作者

钟国防,E-mail: gfzhong@shou.edu.cn

文章历史

收稿日期:2020-05-06
收修改稿日期:2020-05-25
芽孢杆菌有氧发酵豆粕替代鱼粉对大口黑鲈幼鱼生长性能、血清生化指标及肠组织结构的影响
钟国防 1,2,3, 田鑫鑫 1, 谢春元 4, 黄旭雄 1,2,3, 陈乃松 1,2,3, 黄卫 5, 朱站英 5     
1. 上海海洋大学水产科学国家级实验教学示范中心 上海 201306;
2. 上海海洋大学农业农村部鱼类营养与环境生态研究中心 上海 201306;
3. 上海海洋大学农业农村部淡水水产种质资源重点实验室 上海 201306;
4. 上海希杰商贸有限公司 上海 201228;
5. 湖州海皇生物科技有限公司 浙江 湖州 313105
摘要:芽孢杆菌(Bacillus)有氧发酵豆粕的肽类和活菌等含量丰富,为研究其替代鱼粉对大口黑鲈(Micropterus salmoides)幼鱼的养殖效果,配制鱼粉含量为50%的大口黑鲈基础饲料,在基础饲料中用芽孢杆菌有氧发酵豆粕分别替代0、10%、20%、30%和40%的鱼粉,配制成5种等氮、等能实验饲料进饲养实验。实验共分5个组,每组3个重复,每个重复30尾鱼[初始体重为(19.83±0.33) g]。采用表观饱食投喂饲养75 d。结果显示,20%和30%实验组增重率显著高于对照组(P < 0.05),但饲料效率、存活率与对照组无显著差异(P > 0.05),20%的替代组增重率及饲料效率皆出现最大值;各实验组之间肥满度和肝体比均无显著差异(P > 0.05),但替代组脏体比出现下降的趋势,且当替代量超过30%时,显著低于对照组(P < 0.05)。血清白蛋白含量各组间无显著性差异(P > 0.05),替代组总蛋白和球蛋白的含量显著高于对照组(P < 0.05)谷丙转氨酶和谷草转氨酶活力随鱼粉替代量的增加而显著升高,10%组与对照组无显著差异(P > 0.05),其他各替代组显著高于对照组(P < 0.05)。对肠道组织结构的研究结果显示,40%组前肠肠绒毛密度和肠壁厚度均显著低于对照组;30%前肠绒毛高度和宽度显著高于其他各组(P < 0.05)。10%组中肠肠壁厚度显著高于对照组(P < 0.05),但与其他各实验组与对照组无显著差异(P > 0.05);20%和40%组中肠绒毛密度和高度显著低于对照组(P < 0.05)。各实验组的后肠肠壁厚度显著低于对照组(P < 0.05),但30%组绒毛高度和宽度均显著高于对照组(P < 0.05)。综上所述,在本实验条件下,芽孢杆菌有氧发酵豆粕替代20%的鱼粉不会影响大口黑鲈的生长性能和体质,对其肠道健康有一定的促进作用。
关键词大口黑鲈    芽孢杆菌有氧发酵豆粕    生长性能    血清生化    肠组织结构    
Effects of Replacing Fish Meal with Bacillus Aerobically Fermented Soybean Meal on the Growth Performance, Serum Biochemical Indices and Intestinal Histology of Largemouth Bass (Micropterus salmoides)
ZHONG Guofang 1,2,3, TIAN Xinxin 1, XIE Chunyuan 4, HUANG Xuxiong 1,2,3, CHEN Naisong 1,2,3, HUANG Wei 5, ZHU Zhanying 5     
1. National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai 201306, China;
2. Centre for Research on Environmental Ecology and Fish Nutrition (CREEFN), Ministry of Agriculture and Rural Affairs, Shanghai Ocean University, Shanghai 201306, China;
3. Key Laboratory of Freshwater Aquatic Genetic Resources, Ministry of Agriculture and Rural Affairs, Shanghai Ocean University, Shanghai 201306, China;
4. CJ International Trading CO., LTD, Shanghai 201228, China;
5. Huzhou Haihuang Biotechnology Co., Ltd, huzhou, Zhejiang 313105, China
Abstract: This experiment was conducted to study the effects of Bacillus aerobically fermented soybean meal (FSBM) on the growth performance, serum biochemical indices, and intestinal structure of largemouth bass (Micropterus salmoides). Five isoproteic and isoenergetic diets were formulated. A high fish meal (FM) diet containing 50% white fish meal was used as a control diet (0); FSBM was used to replace 10%, 20%, 30%, and 40% of the FM in the control diet to obtain the other experimental four diets. Largemouth bass [with initial body weight of (19.83±0.33) g] were randomly divided into five groups and reared in an indoor cage system for 75 d. Each group had 3 replicates, and each replicate contained 30 fish. The results showed that the weight gain rates of the 20% and 30% trial groups were significantly higher than that of the control group (P < 0.05), but there was no significant difference in feed efficiency and survival rate in all experimental groups (P > 0.05). There were no significant differences in either condition factor or hepatosomatic index between all trial groups (P > 0.05); but the viscerosomatic index was significantly lower than that of the control group (P < 0.05). There was no significant difference in serum albumin in all trial groups (P > 0.05); the total protein and globulin of experimental groups were significantly higher than those of the control group (P < 0.05); the serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities of the trial groups were significantly higher than those of the control group (P < 0.05); In the 30% and 40% FSBM treatments, the intestinal muscular layer appeared thinner and villi integrity dropped. These results indicate that at least 20% of dietary FM protein in the diets of juvenile largemouth bass can be replaced by FSBM without having any adverse effect on growth performance, physical fitness, and intestinal health.
Key words: Largemouth bass    Bacillus aerobic fermentation of soybean meal    Growth performance    Serum biochemical Indices    Intestinal tissue morphology    

鱼粉由于蛋白含量高、适口性好、氨基酸平衡,钙、磷、碘、硒等含量高以及维生素种类较多等特点,是水产饲料中不可缺少的优质蛋白源(姚俊鹏等, 2015),但随着世界渔业养殖规模的迅速发展以及渔获量的减少,导致鱼粉的价格持续走高,养殖成本显著提高,因此,鱼粉替代蛋白源的研究一直为饲料研究的热点(饶远等, 2019; 胡鹏莉等, 2019; Zhong et al, 2011)。豆粕的蛋白质含量高,氨基酸丰富,且有异黄酮等活性物质(Kishida et al, 2000),是较为重要的鱼粉蛋白替代原料。但普通豆粕有多种抗营养因子,过量使用不仅会降低水产动物对营养物质的吸收和利用,而且会对水产动物的消化系统和免疫系统造成损伤(Dunsford et al, 1989),导致其在水产饲料中的应用比例受到限制。研究表明,豆粕经过微生物发酵得到的发酵豆粕(fermented soybean meal, FSBM)可有效降解其抗营养因子,并将大分子的大豆蛋白降解为小分子的蛋白、多肽及小肽等,且发酵过程中产生的益生菌、寡糖、乳酸、微生物和未知生长因子等活性物质能有效提高营养物质的吸收率(Hong et al, 2004; 李宝圣等, 2016; 张成等, 2018)。发酵豆粕产品开发,挖掘了豆粕蛋白在水产饲料中的应用潜力。刘兴旺等(2010)发现,卵形鲳鲹(Trachinotus ovatus)饲料中发酵豆粕替代鱼粉的水平(60.8%)显著高于普通豆粕(45.1%)。黄雄斌等(2010)发现,对方正鲫(Carassius auratus gibelio),发酵豆粕能替代50%鱼粉,而普通豆粕只能替代25%的鱼粉。适量的发酵豆粕替代鱼粉对鱼虾的生长无不良影响(吕云云等, 2016; 刘韬等, 2018; 杨景丰等, 2018),但这些研究所用的发酵豆粕主要是以乳酸菌(Lactobacillus)为主的厌氧发酵产品。

发酵工艺对发酵豆粕产品的品质有重要影响(吴明海等, 2018)。芽孢杆菌(Bacillus)有氧发酵工艺由于发酵条件相对苛刻,特别是发酵过程中引发的产物黏稠,很难持续营造有氧环境,能全程有氧发酵的生产厂家很少。传统的以厌氧乳酸菌为主的发酵工艺对豆粕抗营养因子特别是大分子蛋白(主要是抗原蛋白)的去除能力有限,仅能去掉14%~17.88%的大分子蛋白(表 1),而本研究所用的以芽孢杆菌有氧发酵后的产品,分子质量为10~30 kDa的小分子蛋白含量达26.38%,而对大分子蛋白的去除率达54.15%,能有效提高大分子蛋白的降解能力(表 1),且发酵产品富含芽孢杆菌有益菌,产品质量优良。目前,在水产上的应用比较有限,仅见虹鳟(Oncorhynchus mykiss) (Moniruzzaman et al, 2018)、凡纳滨对虾(Litopenaeus vannamei) (van Nguyen et al, 2018)和岩鱼(Sebastes schlegeli) (Lee et al, 2016)等几个品种,芽孢杆菌有氧发酵豆粕在大口黑鲈(Micropterus salmoides)上的应用研究还未见报道。

表 1 乳酸菌厌氧发酵与芽孢杆菌有氧发酵对豆粕蛋白质的降解差异 Tab.1 The difference of protein degradation on lactic acid bacteria fermented soybean meal and Bacillus aerobic fermentation of soybean meal

大口黑鲈又名加州鲈鱼,是一种典型的肉食性鱼类,其对饲料中蛋白质的营养需求较高(大于37%) (李二超等, 2011)。2018年,我国大口黑鲈的产量达43万t,其中,全程投喂配合饲料养殖的比例超过50%,且大口黑鲈配合饲料中鱼粉含量较高,一般为50%~55%,少数产品甚至达到60%。因此,研究大口黑鲈饲料中鱼粉的替代具有极其重要的意义。本实验研究芽孢杆菌有氧发酵豆粕替代鱼粉对大口黑鲈生长性能、血清生化指标及肠道组织结构的影响,旨在为开发大口黑鲈高效、绿色环保、功能性饲料提供理论支持。

1 材料与方法 1.1 实验设计及实验饲料

根据大口黑鲈的营养需求,配制鱼粉含量为50%的基础饲料(FM),用芽孢杆菌有氧发酵豆粕分别替代FM组10%(FSBM10)、20%(FSBM20)、30%(FSBM30)和40%(FSBM40)的鱼粉,配制5种等氮、等能的实验饲料(表 2)。芽孢杆菌有氧发酵豆粕(粗蛋白56.9%、粗脂肪2%)由上海希杰商贸有限公司提供,其他原料由湖州海皇生物科技有限公司提供。原料粉碎后,过60目筛,按饲料配方称重,逐级混匀,加入适量的水,混匀后过10目筛,用制粒机制粒,烘箱熟化后于60℃烘干18 h,包装后置于-20℃冰箱保存备用。

表 2 饲料组成和营养水平(%风干样品) Tab.2 Composition and nutrient levels of diets (% air dry basis)
1.2 养殖管理

实验在上海海洋大学滨海基地室内养殖池网箱(1.0 m×1.0 m×1.2 m)中进行。大口黑鲈幼鱼苗购自上海秦皇山渔业有限公司,幼鱼运到基地后先暂养14 d并用基础饲料进行驯化。暂养结束挑选形态正常、体质健康、规格均匀的450尾鱼随机分到15个网箱中。实验分5组,每组3个重复,每个重复30尾鱼。每天饱食投喂2次(07:00和18:00),投饲后1 h收集残饵。每周测定水质指标,养殖期间水温为(29.0± 3.5)℃,pH值为8.5±0.5,溶解氧(DO)为4.0~5.0 mg/L,氨氮为0~0.03 mg/L。养殖实验持续75 d。

1.3 样品采集

养殖实验结束后,停食24 h,每平行随机取6尾鱼,分别测量鱼体质量与体长,冰上分离内脏与肝脏并称重记录,用于计算体质指标。尾部抽血,放入3个2 mL离心管中,离心(10 min, 8000 r/min, 4℃)分离血清备用。

1.4 测定指标和方法

实验结束后捞出网箱中鱼,计数称重,并计算成活率、增重率和饲料系数。计算方法如下:

存活率(survival rate, SR, %)=100×实验结束时尾数/实验开始时尾数;

增重率(weight gain rate, WGR, g)=[(末体重-初始体重)/初始体重]×100%;

饲料效率(feed efficiency, FE)=(末体重-初始体重+死亡体重)/(投料量-残饵量);

饲料营养成分测定:水分测定采用105℃常压干燥法,粗灰分测定采用550℃灼烧法,粗蛋白质测定采用杜马斯燃烧法(Etheridge et al, 1998),粗脂肪测定采用氯仿-甲醇法(黄凯等, 2011)。

血清中碱性磷酸酶(ALP)、白蛋白、总蛋白、球蛋白、谷丙转氨酶(ALT)和谷草转氨酶(AST)采用江苏南京建成生物工程研究所购试剂盒测定。

1.5 肠组织切片制作及观察

养殖实验结束后,饥饿24 h,每个重复随机取3尾鱼,冰上分离并取前肠、中肠和后肠组织各2~ 3 cm,生理盐水冲洗后,用滤纸擦干表面水分后放入Bouin氏液中,24 h内换用70%的酒精保存。制作切片时,组织样本乙醇梯度脱水,二甲苯透明处理,石蜡包埋,切片(5 μm),随后进行展片、烤片、H & E染色和封片等系列工作(夏青等, 2015; 陈晓瑛等, 2018)。

1.6 数据处理

实验数据采用SPSS 17.0软件进行单因子方差分析(one-way ANOVA, LSD),若存在显著差异,则进行Duncan多重比较。所有统计值均以平均值±标准差(Mean±SD)表示,显著水平定为P < 0.05。

2 结果 2.1 芽孢杆菌有氧发酵豆粕替代鱼粉对大口黑鲈幼鱼生长性能的影响

表 3可知,适量的芽孢杆菌有氧发酵豆粕能显著提高大口黑鲈幼鱼的增重率(P < 0.05),且随着发酵豆粕替代鱼粉用量的增加呈先上升后下降的趋势,10%组与对照组无显著差异,替代量20%组的生长性能最好并显著优于其他各实验组(P < 0.05),但当替代量达到40%时,增重率与对照组无显著差异(P > 0.05);各实验组的饲料效率并无显著差异(P > 0.05)。各实验组间存活率也无显著差异(P > 0.05)。

表 3 芽孢杆菌有氧发酵豆粕替代鱼粉对大口黑鲈生长性能的影响 Tab.3 Effects of replacement of FM by FSBM on growth indices of M. salmoides
2.2 芽孢杆菌有氧发酵豆粕替代鱼粉对大口黑鲈血清生化指标的影响

表 4可知,大口黑鲈血液中的白蛋白含量随替代量的增加先上升后下降,在20%组出现最大值,但各组间无显著差异(P > 0.05);实验组总蛋白和球蛋白的含量显著高于对照组(P < 0.05);谷丙转氨酶活力随鱼粉替代量的增加而显著升高,10%组与对照组无显著差异(P > 0.05),其他各替代组显著高于对照组(P < 0.05)。10%组的谷草转氨酶活力与对照组无显著差异,但其他各替代组显著高于对照组(P < 0.05)。

表 4 芽孢杆菌有氧发酵豆粕对大口黑鲈血清生化指标的影响 Tab.4 Effects of replacement of FM by FSBM on biochemical indices in serum of M. salmoides
2.3 发酵豆粕替代鱼粉对大口黑鲈形体指标的影响

表 5可知,肥满度随着鱼粉替代量的增加呈先上升后下降的趋势,在20%替代量时出现最大值,但无显著差异(P > 0.05);肝体比随着替代量的增加呈下降的趋势,但各组之间无显著差异(P > 0.05);随着替代量的增加,替代组脏体比出现下降趋势,且当替代量超过30%时,显著低于对照组(P < 0.05)。

表 5 芽孢杆菌有氧发酵豆粕替代鱼粉对大口黑鲈形体指标的影响 Tab.5 Effects of replacement of FM by FSBM on morphometry of M. salmoides
2.4 芽孢杆菌有氧发酵豆粕替代鱼粉对大口黑鲈肠道组织结构的影响

肠道切片形态结构显微观察发现,前肠对照组大口鲈的肠绒毛结构完整,发育良好,杯状细胞较多且排列密集有序,但40%组肠绒毛密度稍有降低,有绒毛脱落;后肠组织中观察到上皮细胞和肌肉层的分离现象,40%组肠绒毛的完整性降低,肠绒毛减少,杯状细胞数量减少,并且肠黏膜层与肠肌层之间的连接明显变得疏松(图 1)。

图 1 芽孢杆菌有氧发酵豆粕替代鱼粉对大口黑鲈肠道组织结构的影响 Fig.1 Effects of replacement of FM by FSBM on intestinal tissue structure of M. salmoides 1~5:0、10%、20%、30%和40%组的前肠组织;6~10:0、10%、20%、30%和40%组的中肠组织;11~15:0、10%、20%、30%和40%组的后肠组织MT-肌层厚度;SM-黏膜下层;GC-空泡;PL-绒毛长度;PW-绒毛宽度;IV-微绒毛 1~5: 0, 10%, 20%, 30%, and 40% groups of anterior intestine; 6~10: 0, 10%, 20%, 30%, and 40% groups of middle intestine; 11~15: 0, 10%, 20%, 30%, and 40% groups of distal intestine MT-muscular thickness; SM-submucosa; GC-cavity; PL-villi length; PW-villi width; IV-microvilli

表 6可知,随着发酵豆粕替代的增加,前肠的肌层厚度呈显著下降的趋势(P < 0.05),各实验组前肠的绒毛长度和绒毛宽度均显著大于对照组(P < 0.05)。

表 6 芽孢杆菌有氧发酵豆粕替代鱼粉对大口黑鲈肠道组织结构的影响 Tab.6 Effects of replacement of FM by FSBM on intestinal tissue structure of M. salmoides

中肠肌层厚度各实验组显著低于对照组(P < 0.05),绒毛长度除10%组显著大于对照组外,其他各实验组显著小于对照组(P < 0.05),而绒毛宽度各组间无显著差异(P > 0.05)。

后肠肌层厚度20%和30%组显著大于对照组,而其他实验组显著小于对照组(P < 0.05),30%组绒毛长度显著大于其他各组,20%和40%组绒毛长度显著小于对照组(P < 0.05),绒毛宽度20%和30%组显著大于对照组(P < 0.05)。

3 讨论 3.1 芽孢杆菌有氧发酵豆粕对大口黑鲈幼鱼生长性能的影响

豆粕替代鱼粉受到限制主要是因为抗营养因子对鱼生长的消极影响,而对豆粕抗营养因子的研究推动了发酵豆粕产品的快速发展。以乳酸菌厌氧发酵制得的发酵豆粕与普通豆粕相比,在鱼类的生长性能、消化吸收及对鱼类消化生理结构的影响方面都有积极效应。鱼类饲料中不同工艺处理后的发酵豆粕能替代16%~40%的鱼粉(Barnes et al, 2015; Yaghoubi et al, 2016),豆粕处理及发酵工艺的不同对抗营养因子的去除能力也不一样,芽孢杆菌有氧发酵工艺对大分子蛋白的降解能力优于传统的乳酸菌厌氧发酵(表 1),对豆粕抗营养因子的处理能力有显著提高。

发酵豆粕替代鱼粉的潜力与发酵豆粕产品生产工艺及养殖对象的食性有密切关系。本实验研究芽孢杆菌有氧发酵在大口黑鲈饲料中替代鱼粉的潜力,养殖实验结束后发现,20%~30%替代组均表现出较佳的生长性能。Azarm等(2014)研究发现,能用乳酸菌厌氧发酵豆粕替代40%的鱼粉饲喂黑鲷(Acanthopagrus schlegeli)。Barnes等(2015)发现,能用乳酸菌厌氧发酵豆粕替代35%的鱼粉饲喂虹鳟(Oncorhynchus mykiss)。Zhang等(2014)研究发现,能用γ射线照射后的豆粕替代16%的鱼粉饲喂日本花鲈(Lateolabrax japonicus)。Kokou等(2012)研究发现,能用生物处理豆粕替代近40%的鱼粉饲喂金头鲷(Sparus aurata)。芽孢杆菌有氧发酵豆粕替代鱼粉的研究目前也有相关报道,如在虹鳟、凡纳滨对虾和岩鱼(Moniruzzaman et al, 2018; van Nguyen et al, 2018; Lee et al, 2016)替代鱼粉的量分别为30%、25.36%和40%。

本研究20%~30%实验组比对照组显著提高了增重率,可能是由于发酵后大分子蛋白质被大量分解为多肽和小肽,提高了吸收效率。游离氨基酸的吸收是逆浓度梯度的转运,要通过不同的Na+转运系统才能完成(Matthews, 1980),且游离氨基酸在吸收时有相互竞争,需要消耗较多的能量。小肽的吸收不通过水解,而是通过特殊的转运系统,完整地进入血液中(Jalkanen et al, 2004)。因此,小肽比游离氨基酸更有利于鱼类吸收,能提高鱼类高蛋白质的合成效率。此外,植物蛋白替代鱼粉最大的不利因素是缺乏一些必需氨基酸(Kader et al, 2012; Zhang et al, 2014; Jo et al, 2017),导致在吸收时会影响氨基酸在体内合成蛋白质的效率,而以小肽的形式直接吸收可能会避免这种缺陷,其具体的吸收合成过程还有待于进一步开展相关的生理实验来证实。

3.2 芽孢杆菌有氧发酵豆粕对大口黑鲈幼鱼血清生化指标的影响

鱼类的血液指标能充分反映鱼体的生理和健康状态(Maita, 2007),生理或病理因素都会导致它们的变化。血清白蛋白主要反映机体营养能力,而球蛋白与免疫能力相关。实验结果显示,鱼粉替代量在30%以内时,实验组血清白蛋白略有升高,说明适宜的替代鱼粉对机体的营养能力没有影响。但替代组的球蛋白显著高于对照组,表明替代后导致机体免疫系统活跃。

谷丙转氨酶、谷草转氨酶是机体分布最广、活性最强的转氨酶,通常作为评估肝脏健康状况的指示酶(Krajnovic-Ozretic, 1991)。鱼类与哺乳动物一样,当组织或器官受到功能性损伤时,某些特有的细胞酶会释放到血液里而被检测出来(Bouck et al, 1975)。正常情况下,转氨酶主要存在于肝脏。肝功能障碍或肝细胞受损时,谷丙转氨酶和谷草转氨酶会释放到血液中,引起血清转氨酶活性的升高(Kaplan, 1979)。实验组谷丙转氨酶与谷草转氨酶随着替代量的增加而升高且均显著高于对照组,表明大口黑鲈摄食替代鱼粉饲料后,肝脏产生了应激。养殖鱼虾投喂植物蛋白含量高的饲料容易出现营养性脂肪肝,主要是因为植物蛋白含有大量的抗营养因子(吴莉芳等, 2006; 陈晓明等, 2015)。本实验鱼没有发现有明显的绿肝、花肝等病变,可能是因为相对于养殖生产实验饲养时间较短,且芽孢杆菌有氧发酵后清除了大量的抗营养因子。但长期应激是否产生肝功能障碍等不良影响,还有待于进一步进行中试验证。这也提示在实际生产时,芽孢杆菌有氧发酵豆粕替代鱼粉的量要从生长、生理及病理等多个因素综合评测。

3.3 芽孢杆菌有氧发酵豆粕对大口黑鲈幼鱼形体指标的影响

本研究的形体指标中实验组肝体比有明显下降的趋势,但与对照组无显著差异,这与Kokou等(2012)Yaghoubi等(2016)的研究结果相似,这可能是因为实验时间较短所致(Qiu et al, 2018)。肝体比增加与许多因素有关,如必需氨基酸低也会导致养殖对象肝体比的增大(Espe et al, 2010)。而本研究中,肝体比没有增加,说明发酵豆粕中丰富的小分子量蛋白质、小肽等可以弥补必需氨基酸少的缺陷。本研究20%和30%组的脏体比显著低于对照组,这一结果要优于王新霞(2009)的研究结果,其研究表明,加州鲈饲料中添加10%以内的发酵豆粕,能显著降低脏体比和肝体比,降低了脂肪在体内的沉积,从而降低脂肪肝的发生率,而本研究20%和30%组脏体比均为下降。这可能是因为本研究饲料的营养组成中小肽含量丰富,以小肽吸收能促进幼鱼的快速生长,对能量的需求加大,促使饲料中的糖类更多地用于能量消耗,而转化为脂肪储存相对较少。这种推断需要进一步研究糖的代谢来证实。同时,小肽能促进“脂质代谢”(Drevon, 2005),也会减少脂肪在内脏的沉积,致使脏体比下降。

3.4 芽孢杆菌有氧发酵豆粕对大口黑鲈幼鱼肠道组织结构的影响

肠道绒毛高度、密度以及杯状细胞的数量等组织形态学指标反映鱼类肠道的发育和健康程度,通常作为评估鱼类肠道的消化吸收能力的依据(聂国兴等, 2007; 王坛等, 2019)。植物蛋白替代鱼粉会导致肠道组织结构发生变化。芽孢杆菌有氧发酵豆粕替代鱼粉后,尽管适宜替代量(20%和30%替代)促进了大口黑鲈的生长性能,但对肠道组织形态学研究表明,40%的鱼粉替代引起了前肠肌肉层厚度的下降,损害了小肠的完整性。郑银桦等(2015)用混合植物蛋白质替代50%鱼粉后,引起了大口黑鲈肠道肌层变薄,绒毛完整度下降等不良影响,与本研究结果相似。本实验切片观察还发现,替代组前肠绒毛长度和宽度均显著优于对照组,推测绒毛面积的增加促进了营养物质的吸收,从而促进了生长,这与Yamamoto等(2010)在虹鳟中的研究结果相一致。赵柳兰等(2018)研究认为,大口黑鲈前肠皱襞密集而细长,中性黏液细胞多,是大口黑鲈营养物质消化吸收的主要场所,肌肉层厚度下降会影响前肠蠕动的能力,对前肠物理性消化功能会产生不良影响,但绒毛面积增加而引起的吸收功能的提高,弥补了物理消化减弱这个缺陷,这也是20%和30%组生长性能优于对照组的一个极为重要的原因。同时,由于大口黑鲈为有胃鱼,胃的蠕动减少了肠道蠕动的压力,因此,营养物质经过胃和前肠充分的消化吸收作用以后,中后肠结构的变化对营养物质消化吸收影响就相对有限。杯状细胞分泌黏液协助消化和保护胃肠道组织免受损伤(Cerezuela et al, 2013; Khosravi et al, 2015)。本研究表明,鱼粉替代对前肠杯状细胞没有不良影响,但替代量达到40%时,后肠杯状细胞数量明显减少。Bakke-McKellep等(2007)研究发现,在豆粕型日粮中添加益生元和益生菌后,通过微生物的调控可以改变杯状细胞的数量。饲料中的芽孢杆菌对虹鳟小肠的杯状细胞的形成有促进作用(Ramos et al, 2017),本研究所用的发酵豆粕含有丰富的芽孢杆菌,这可能是导致前肠杯状细胞不受影响的主要原因。与之相反,Khosravi等(2015)研究认为,大豆浓缩蛋白会导致杯状细胞数量的减少,可能是大豆浓缩蛋白对抗营养因子的去除能力有限所致。

4 结论

芽孢杆菌有氧发酵豆粕能显著增加饲料小分子蛋白、肽类的含量,适量替代鱼粉能促进大口黑鲈的生长,且能降低脏体比。但同时引起了转氨酶活性的升高,增加了营养应激程度,长期饲喂会使生长受阻。替代量太高会引起肠组织结构的损伤,从而影响消化吸收。因此,在本研究中,综合考虑生长、形体指标和消化道组织结构等多方面因素,大口黑鲈饲料中芽孢杆菌有氧发酵豆粕替代20%的鱼粉能达到理想的效果。

参考文献
AZARM H M, LEE S M. Effects of partial substitution of dietary fish meal by fermented soybean meal on growth performance, amino acid and biochemical parameters of juvenile black sea bream Acanthopagrus schlegeli. Aquaculture Research, 2014, 45(6): 994-1003 DOI:10.1111/are.12040
BAKKE-MCKELLEP A M, PENN M H, SALAS P M, et al. Effects of dietary soyabean meal, inulin and oxytetracycline on intestinal microbiota and epithelial cell stress, apoptosis and proliferation in the teleost Atlantic salmon (Salmo salar L). British Journal of Nutrition, 2007, 97(4): 699-713 DOI:10.1017/S0007114507381397
BOUCK G R, SCHNEIDER P W, JACOBSON J, et al. Characterization and subcellular localization of leucine aminonaphthylamidase (LAN) in rainbow trout (Salmo gairdneri). Journal of the Fisheries Research Board of Canada, 1975, 32(8): 1289-1295 DOI:10.1139/f75-150
BARNES M E, BROWN M L, NEIGER R. Comparative performance of two rainbow trout strains fed fermented soybean meal. Aquaculture International, 2015, 23(5): 1227-1238 DOI:10.1007/s10499-015-9879-6
DREVON C A. Fatty acids and expression of adipokines. Biochimica et Biophysica Acta (BBA)—Molecular Basis of Disease,, 2005, 1740(2): 287-292 DOI:10.1016/j.bbadis.2004.11.019
CHEN X M, HUA X M, ZHU W X, et al. Effects of soybean allergic proteins on growth, digestion and non-specific immune of Litopenaeus vannamei. Chinese Journal of Animal Nutrition, 2015, 27(7): 2115-2127 [陈晓明, 华雪铭, 朱伟星, 等. 大豆抗原蛋白对南美白对虾生长、消化及非特异性免疫的影响. 动物营养学报, 2015, 27(7): 2115-2127 DOI:10.3969/j.issn.1006-267x.2015.07.017]
CHEN X Y, WANG G X, SUN Y P, et al. Effects of dietary xylo-oligosaccharides on digestive enzymes activities, intestinal morphology and bacteria numbers of juvenile Litopenaeus vannamei. Chinese Journal of Animal Nutrition, 2018, 30(4): 1522-1529 [陈晓瑛, 王国霞, 孙育平, 等. 饲料中添加低聚木糖对凡纳滨对虾幼虾消化酶活力、肠道形态及细菌数量的影响. 动物营养学报, 2018, 30(4): 1522-1529 DOI:10.3969/j.issn.1006-267x.2018.04.037]
CEREZUELA R, FUMANAL M, TAPIA-PANIAGUA S T, et al. Changes in intestinal morphology and microbiota caused by dietary administration of inulin and Bacillus subtilis in gilthead sea bream (Sparus aurata L) specimens. Fish and Shellfish Immunology, 2013, 34(5): 1063-1070 DOI:10.1016/j.fsi.2013.01.015
DUNSFORD B R, KNABE D A, HAENSLY W E. The effect of dietary soybean meal on the microscopic anatomy of the small intestine in the early-weaned pig. Journal of Animal Science, 1989, 67(7): 1855-1860 DOI:10.2527/jas1989.6771855x
ESPE M, RATHORE R M, DU Z Y, et al. Methionine limitation results in increased hepatic FAS activity, higher liver 18: 1 to 18: 0 fatty acid ratio and hepatic TAG accumulation in Atlantic salmon, Salmo salar. Amino Acids, 2010, 39: 449-460 DOI:10.1007/s00726-009-0461-2
ETHERIDGE R D, PESTI G M, FOSTER E H. A comparison of nitrogen values obtained utilizing the Kjeldahl nitrogen and Dumas combustion methodologies (Leco CNS 2000) on samples typical of an animal nutrition analytical laboratory. Animal Feed Science and Technology, 1998, 73(1): 21-28
ZHONG G F, YUAN K, HUA X M, et al. Effect of CGM on growth performance and digestibility in puffer (Takifugu fasciatus). Aquaculture International, 2011, 19(3): 395-403 DOI:10.1007/s10499-010-9355-2
HONG K J, LEE C H, KIM S W. Aspergillus oryzae GB-107 fermentation improves nutritional quality of food soybeans and feed soybean meals. Journal of Medicinal Food, 2004, 7(4): 430-435 DOI:10.1089/jmf.2004.7.430
HU P L, WU R, LU K L, et al. Effects of replacing fish meal with composite protein on growth, diet digestibility, and gut health in Japanese seabass (Lateolabrax maculatus). Progress in Fishery Sciences, 2019, 40(6): 56-65 [胡鹏莉, 吴瑞, 鲁康乐, 等. 复合蛋白替代鱼粉对花鲈生长、消化能力和肠道健康的影响. 渔业科学进展, 2019, 40(6): 56-65]
HUANG K, WU H Y, ZHU D G, et al. Effects of dietary lipid levels on growth and fatty acid composition in hepatopancreas and muscle of Pacific white leg shrimp Litopenaeus vannamei. Fishery Sciences, 2011, 30(5): 249-255 [黄凯, 吴宏玉, 朱定贵, 等. 饲料脂肪水平对凡纳滨对虾生长, 肌肉和肝胰腺脂肪酸组成的影响. 水产科学, 2011, 30(5): 249-255 DOI:10.3969/j.issn.1003-1111.2011.05.001]
HUANG X B, LI F G, et al. The replacement of fishmeal by fermented soybean meal and soybean meal in compound diets of Carassius auratus. Hunan Agricultural Sciences, 2010(13): 143-145 [黄雄斌, 李国富, 等. 方正鲫饲料中发酵豆粕和豆粕替代鱼粉的研究. 湖南农业科学, 2010(13): 143-145 DOI:10.3969/j.issn.1006-060X.2010.13.046]
JALKANEN K J, ELSTNER M, SUHAI S. Amino acids and small peptides as building blocks for proteins: Comparative theoretical and spectroscopic studies. Journal of Molecular Structure: THEOCHEM, 2004, 675(1): 61-77
JO H Y, LEE S H, YUN H, et al. Evaluation of dietary fishmeal analogue with addition of shrimp soluble extract on growth and nonspecific immune response of rainbow trout, Oncorhynchus mykiss. Journal of the World Aquaculture Society, 2017, 48(4): 583-591 DOI:10.1111/jwas.12355
KAPLAN A. Clinical chemistry: Interpretation and technique. London: Lea and Febiger, 1979: 109-111
KADER A, KOSHIO S, ISHIKAWA M, et al. Can fermented soybean meal and squid byproduct blend be used as fishmeal replacements for Japanese flounder (Paralichthys olivaceus)?. Aquaculture Research, 2012, 43(10): 1427-1438 DOI:10.1111/j.1365-2109.2011.02945.x
KRAJNOVIC-OZRETIC M. Serum enzymes in fish as biochemical indicators of marine pollution. Map Technical Reports, 1991, 48: 1-11
KHOSRAVI S, RAHIMNEJAD S, HERAULT M, et al. Effects of protein hydrolysates supplementation in low fish meal diets on growth performance, innate immunity and disease resistance of red sea bream Pagrus major. Fish and Shellfish Immunology, 2015, 45(2): 858-868 DOI:10.1016/j.fsi.2015.05.039
KISHIDA T, ATAKI H, TAKEBE M, et al. Soybean meal fermented by Aspergillus awamori increases the cytochrome P-450 content of the liver microsomes of mice. Journal of Agricultural and Food Chemistry, 2000, 48(4): 1367-1372 DOI:10.1021/jf9905830
KOKOU F, RIGOS G, HENRY M, et al. Growth performance, feed utilization and non-specific immune response of gilthead sea bream (Sparus aurata L.) fed graded levels of a bioprocessed soybean meal. Aquaculture, 2012, 364: 74-81
QIU X, BUENTELLO A, SHANNON R, et al. Evaluation of three non-genetically modified soybean cultivars as ingredients and a yeast-based additive as a supplement in practical diets for Pacific white shrimp Litopenaeus vannamei. Aquaculture Nutrition, 2018, 24(1): 173-183 DOI:10.1111/anu.12545
LI B S, ZHANG L, MI H F, et al. Nutritional characteristics of fermented soybean meal and its application in aquatic feed. Scientific Fish Farming, 2016, 32(1): 67-69 [李宝圣, 张璐, 米海峰, 等. 发酵豆粕的营养特性及其在水产饲料中的应用研究. 科学养鱼, 2016, 32(1): 67-69]
LI E C, CHEN L Q. Research progress on nutritional needs of Micropterus salmoides. Modern Agricultural Technology, 2011(21): 312-316 [李二超, 陈立侨. 大口黑鲈的营养需要研究进展. 现代农业科技, 2011(21): 312-316 DOI:10.3969/j.issn.1007-5739.2011.21.198]
LIU T, HUANG X X, SU M F, et al. Effects of fermented soybean meal replacing fish meal on the growth performance, immune-related enzymes and gene expression of Litopenaeus vannamei. Journal of Fisheries of China, 2018, 42(9): 1417-1426 [刘韬, 黄旭雄, 苏美英, 等. 发酵豆粕替代鱼粉对凡纳滨对虾生长、免疫相关酶及免疫相关基因表达的影响. 水产学报, 2018, 42(9): 1417-1426]
LIU X F, WANG H L, ZHANG H T, et al. Effects of fish meal in diets replaced by soybean meal and fermented soybean meal on growth performance and feed intake in Pompano. China Feed, 2010(18): 22-29, 36 [刘兴旺, 王华朗, 张海涛, 等. 豆粕和发酵豆粕替代鱼粉对卵形鲳鲹摄食生长的影响. 中国饲料, 2010(18): 22-29, 36]
LÜ Y Y, CHANG Q, CHEN S Q, et al. The effects of dietary fermented soybean meal on the growth and digestive ability of spotted halibut, Verasper variegatus. Acta Hydrobiologica Sinica, 2016, 40(1): 10-18 [吕云云, 常青, 陈四清, 等. 发酵豆粕对圆斑星鲽生长及消化能力的影响. 水生生物学报, 2016, 40(1): 10-18]
MATTHEWS D M. Intestind absorption of peptides. Physiological Reviews, 1980, 24: 734
MONIRUZZAMAN J H, BAE S H, et al. Evaluation of solid- state fermented protein concentrates as a fish meal replacer in the diets of juvenile rainbow trout, Oncorhynchus mykiss. Aquaculture Nutrition, 2018, 24(4): 1-15
MAITA M. Fish health assessment. In: Nakagawa H, Sato M, & Gatlin III DM (Eds. ), Dietary supplements for the health and quality of cultured fish. Washington DC: CABI, 2007, 10-35
NIE G X, WANG J L, ZHU M W, et al. The influences of xylanase added in wheat basal diet on intestine chyme viscosity and the development of villi and microvilli of Tilapia nilotica. Journal of Fisheries of China, 2007, 31(1): 54-61 [聂国兴, 王俊丽, 朱命炜, 等. 小麦基础饲料添加木聚糖酶对尼罗罗非鱼肠道食糜粘度和绒毛、微绒毛发育的影响. 水产学报, 2007, 31(1): 54-61]
VAN NGUYEN N, HOANG L, VAN KHANH T, et al. Utilization of fermented soybean meal for fishmeal substitution in diets of Pacific white shrimp (Litopenaeus vannamei). Aquaculture Nutrition, 2018, 24(3): 1092-1100 DOI:10.1111/anu.12648
RAMOS M A, GONÇALVES J F, COSTAS B, et al. Commercial bacillus probiotic supplementation of rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta): Growth, immune responses and intestinal morphology. Aquaculture Research, 2017, 48(5): 2538-2549 DOI:10.1111/are.13090
RAO Y, XIANG X, HUANG X Z, et al. Effects of replacement of fish meal with silkworm powder on growth performance, feed intake, and body composition of juvenile black bass (Micropterus salmonides). Progress in Fishery Sciences, 2019, 40(4): 31-38 [饶远, 向枭, 黄先智, 等. 蚕粉替代鱼粉对加州鲈幼鱼生长、饲料利用及体成分的影响. 渔业科学进展, 2019, 40(4): 31-38]
LEE S M, AZARM H M, CHANG K H. Effects of dietary inclusion of fermented soybean meal on growth, body composition, antioxidant enzyme activity and disease resistance of rockfish (Sebastes schlegeli). Aquaculture, 2016, 459: 110-116 DOI:10.1016/j.aquaculture.2016.03.036
WANG T, ZHAO J X, LIU D L, et al. Effects of dietary lysozyme on the digestive tract structure and nutrient digestibility of GIFT tilapia (Oreochromis niloticus). Progress in Fishery Sciences, 2019, 40(6): 76-87 [王坛, 赵金鑫, 刘东来, 等. 饲用溶菌酶对吉富罗非鱼消化道组织结构和营养物质消化吸收的影响. 渔业科学进展, 2019, 40(6): 76-87]
WANG X X. Study on the application of fermented soybean meal instead of fish meal in the feed of Micropterus salmoides. New Feed, 2009, 1: 58-61 [王新霞. 发酵豆粕替代鱼粉在加州鲈饲料中的研究. 新饲料, 2009, 1: 58-61]
WU H M, SUN X W. Effect of aerobic and anaerobic conditions on the quality of fermented soybean meal. Culture and Feed, 2018, 11: 49-51 [吴明海, 孙新文. 好氧与厌氧对发酵豆粕品质的影响. 养殖与饲料, 2018, 11: 49-51]
WU L F, QIN G X, ZHU D, et al. Effects of main antinutritional factors in soybean on fish. Soybean Science, 2006, 25(4): 450-453 [吴莉芳, 秦贵信, 朱丹, 等. 大豆中主要抗营养因子对鱼类的影响. 大豆科学, 2006, 25(4): 450-453 DOI:10.3969/j.issn.1000-9841.2006.04.024]
XIA Q, WANG B J, LIU M, et al. Pathological changes and transcriptional response to immersion infection by Vibrio harveyi in shrimp (Litopenaeus vannamei) gut. Journal of Fisheries of China, 2015(10): 92-100 [夏青, 王宝杰, 刘梅, 等. 哈维氏弧菌浸浴后凡纳滨对虾肠道组织病理变化及转录水平的免疫应答. 水产学报, 2015(10): 92-100]
YANG J F, HUA X M, GUO Z H, et al. Effects of fermented soybean meal replacing fish meal and soybean meal on growth, serum biochemical and immune gene expression of Macrobrachium rosenbergii. Acta Hydrobiologica Sinica, 2018, 42(4): 719-726 [杨景丰, 华雪铭, 郭子好, 等. 发酵豆粕替代鱼粉和豆粕对罗氏沼虾生长、血清生化及免疫基因表达的影响. 水生生物学报, 2018, 42(4): 719-726]
YAGHOUBI M, MOZANZADEH M T, MARAMMAZI J G, et al. Dietary replacement of fish meal by soy products (soybean meal and isolated soy protein) in silvery-black porgy juveniles (Sparidentex hasta). Aquaculture, 2016, 464: 50-59 DOI:10.1016/j.aquaculture.2016.06.002
YAMAMOTO T, IWASHITA Y, MATSUNARI H, et al. Influence of fermentation conditions for soybean meal in a non-fish meal diet on the growth performance and physiological condition of rainbow trout Oncorhynchus mykiss. Aquaculture, 2010, 309(1/2/3/4): 173-180
YAO J P, XIAO Q. Research progress of fish meal substitute protein source in aquaculture. Feed Research, 2015(24): 39-46 [姚俊鹏, 肖勤. 水产养殖中鱼粉替代蛋白源的研究进展. 饲料研究, 2015(24): 39-46]
ZHANG C, HAN K K, LUO S L, et al. Progress in the application of soybean meal. Cereal and Feed Industry, 2018, 380(12): 47-50, 54 [张成, 韩坤坤, 罗世龙, 等. 发酵豆粕的应用研究进展. 粮食与饲料工业, 2018, 380(12): 47-50, 54]
ZHENG G H, PENG C, WU X F, et al. Effects of hydrolyzed yeast on growth performance, lipids metabolism and intestinal structure of largemouth bass (Micropterus salmoides). Chinese Journal of Animal Nutrition, 2015, 27(5): 1605-1612 [郑银桦, 彭聪, 吴秀峰, 等. 酵母酶解物对大口黑鲈生长性能、脂类代谢及肠道组织结构的影响. 动物营养学报, 2015, 27(5): 1605-1612 DOI:10.3969/j.issn.1006-267x.2015.05.033]
ZHAO L L, CHEN Q L, YANG S, et al. Analysis of the histological structure, the types and distribution of mucous cells of digestive tract in largemouth bass (Micropterus samoides). Journal of Sichuan Agricultural University, 2018, 36(4): 549-554 [赵柳兰, 陈侨兰, 杨淞, 等. 大口黑鲈消化道组织结构及黏液细胞的类型和分布. 四川农业大学学报, 2018, 36(4): 549-554]
ZHANG Y Q, WU Y B, JIANG D L, et al. Gamma-irradiated soybean meal replaced more fish meal in the diets of Japanese seabass (Lateolabrax japonicus). Animal Feed Science and Technology, 2014, 197: 155-163 DOI:10.1016/j.anifeedsci.2014.08.002