动物营养学报    2021, Vol. 33 Issue (8): 4231-4243    PDF    
木聚糖酶对肉鸡生长性能和肠道健康的影响
王剑 , 尚庆辉 , 张连华 , 朴香淑     
中国农业大学动物科技学院, 动物营养学国家重点实验室, 北京 100193
摘要: 木聚糖酶已被广泛应用于单胃动物饲粮中,木聚糖酶高效水解木聚糖的作用效果越来越受到关注,尤其在肉鸡的小麦基础饲粮中,旨在改善动物肠道健康。本文结合国内外研究进展,就木聚糖的抗营养特性以及木聚糖酶对肉鸡的促生长和改善肠道健康等作用效果进行了综述。
关键词: 木聚糖酶    肉鸡    肠道健康    
Effects of Xylanases on Growth Performance and Gut Health of Broilers
WANG Jian , SHANG Qinghui , ZHANG Lianhua , PIAO Xiangshu     
State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China
Abstract: At the present, xylanases have been widely applied in monogastric animal diets to improve gut health, especially in wheat-based diets for broilers. The xylanase has attracted extensive attention because it could efficiently hydrolyze xylan. Therefore, combined with the research progress at home and abroad, this paper primarily reviews anti-nutritional effects of xylan, and positive effects of xylanase on growth performance and gut health of broilers.
Key words: xylanase    broiler    gut health    

在肉鸡生产中,饲料成本占总养殖成本的70%~75%[1]。肉鸡饲料以谷物为主,可满足肉鸡对于能量和蛋白质的大部分需求。而通常谷物中80%以上的物质为碳水化合物,其中淀粉占70%~90%,非淀粉多糖(non-starch poly saccharides,NSP)占10%~30%[2]。NSP是一种多糖成分的总称,包括纤维素、半纤维素和果胶等物质,是构成植物细胞壁的主要成分,其通常不能被肉鸡自身所分泌的消化酶水解,具有抗营养作用[1, 3]

阿拉伯木聚糖作为一种植物半纤维素,广泛存在于植物细胞壁中,是小麦、黑麦和燕麦等谷物中一种主要的NSP[4]。木聚糖是一种多聚五碳糖,主链通常由β-吡喃木糖残基以β-1, 4-糖苷键连接而成[1, 5]。由于肉鸡消化道内不能分泌水解木聚糖的内源酶,其在肠道内通常表现出抗营养作用:1)增加肠道食糜黏度;2)“笼蔽效应”,即存在于细胞壁中的NSP将淀粉和蛋白质等养分包裹其中;3)破坏肠道菌群结构;4)改变消化道生理特性[1, 6]。研究表明,饲粮中添加木聚糖酶可高效水解木聚糖,消除其抗营养作用,改善机体肠道健康,从而提高肉鸡生长性能和养分利用率[1]。肠道是机体的最大免疫器官,同时也是养分消化和吸收的主要部位,肠道健康对于动物的生长具有至关重要的意义。因此,本文就木聚糖酶对肉鸡生长性能和肠道健康的影响及作用效果进行阐述,以期为木聚糖酶的高效应用提供参考。

1 木聚糖酶的概述

广义上来说,木聚糖酶是一类可将木聚糖主链和侧链水解的复合酶系。由于木聚糖结构的不均一性,木聚糖的完全降解需多种酶参与共同完成,包括内切1, 4-β-D-木聚糖酶(EC 3.2.1.8)、β-D-木糖苷酶(EC 3.2.1.37)、α-L-阿拉伯呋喃糖酶(EC 3.2.1.55)、α-D-葡萄糖醛酸酶(EC 3.2.1.139)、乙酰木聚糖酯酶(EC 3.1.1.72)、阿魏酸酯酶(EC 3.1.1.73)和香豆酸酯酶(EC 3.1.1-)[7]。其中,内切1, 4-β-D-木聚糖酶和β-D-木糖苷酶为降解木聚糖的2个关键酶,内切1, 4-β-D-木聚糖酶可作用于连接主链的β-1, 4-木糖苷键,从而将木聚糖降解为低聚木糖,而β-D-木糖苷酶可进一步将低聚木糖水解成木糖单体[7-8]。狭义上所说的木聚糖酶是指内切1, 4-β-D-木聚糖酶,它直接参与水解木聚糖主链,被认为是水解木聚糖贡献最大的酶,也是我们在饲料中广泛应用的木聚糖酶。木聚糖酶属于糖苷水解酶(glycoside hydrolases,GH),而GH可分为不同家族,木聚糖酶通常被归为GH10和GH11家族,部分木聚糖酶可能分布在GH5、GH7、GH8、GH26和GH43家族[8]。分布于GH10家族的木聚糖酶一般是大分子质量的酶,其结构为纤维素结合域和催化域由连接肽连接组成,通常是由8个α螺旋和8个β折叠构成的桶状结构;GH11家族木聚糖酶则多为低分子质量的酶,单结构域,通常为双交换的催化机制[8-9]。不同糖苷水解酶降解木聚糖结构的不同位置如图 1所示。

图 1 不同糖苷水解酶降解木聚糖结构的不同位置 Fig. 1 Different positions of degradation of xylan structure by different glycosidic hydrolases[10]

木聚糖酶来源广泛,植物、动物和微生物均可产生木聚糖酶[8]。其中,微生物是木聚糖酶的主要来源,产生木聚糖酶的微生物包括真菌和细菌。在细菌中,芽孢杆菌是报道最为广泛的一种木聚糖酶生产菌,如耐盐芽孢杆菌、短小芽孢杆菌、枯草芽孢杆菌和解淀粉芽孢杆菌等;在真菌中,生产木聚糖酶的则主要包括曲霉、木霉和青霉等菌株[11]表 1列举了不同微生物来源的木聚糖酶的酶学性质。据报道,嗜热毁丝菌(Myceliophthora thermophila)、优化樟绒枝霉(Malbranchea cinnamomea)、绵毛嗜热丝菌(Thermomyces lanuginosus)和金黄色嗜热子囊菌(Thermoascus aurantiacus)等真菌可产生耐高温木聚糖酶;解蛋白粪热杆菌(Caldicellulosiruptor owensensis)、Caldicoprobacter algeriensis和波曲多热孢菌(Thermopolyspora flexuosa)等真菌同样可产生耐高温木聚糖酶,耐高温木聚糖酶在温度高达60~70 ℃时仍有活性[26]。耐冷木聚糖酶目前已在海洋青霉FS010(Penicillium FS010)、木霉SC9(Trichoderma sp. SC9)、Bispora antennata和新耐冷枝孢菌(Cladosporium neopsychrotolerans)等菌株中分离出来[22]。细菌来源的木聚糖酶的最佳pH通常在中性或者碱性范围内,而真菌木聚糖酶的最佳pH通常在酸性范围内[27]

表 1 不同微生物来源的木聚糖酶的酶学性质 Table 1 Enzymatic characterization of xylanases from different microbial sources
2 木聚糖酶的作用效果

目前,国内外关于木聚糖酶消除木聚糖抗营养作用的研究较多,主要包括3点:1)降低肠道食糜黏度;2)破坏植物细胞壁,使被细胞壁包裹的养分得以释放;3)将木聚糖水解成益生元低聚木糖,改善肠道健康。

2.1 降低肠道食糜黏度

水溶性木聚糖由于具有较强的持水性,增加了肠道食糜黏度,阻碍了肠道内容物与肠道内源性消化酶的接触[28]。此外,黏度的增加也会导致小肠黏膜层加厚,从而降低养分吸收速率[29]。Ravn等[30]研究发现,木聚糖酶体外水解小麦、黑麦和大麦的提取物30 min后,各原料黏度均显著降低。Choct等[31]研究发现,小麦基础饲粮中添加木聚糖酶可显著降低肉鸡十二指肠(2.9 mPa·s vs. 1.7 mPa·s)、空肠(4.6 mPa·s vs. 2.3 mPa·s)和回肠食糜黏度(14.0 mPa·s vs. 3.9 mPa·s)。Kiarie等[32]研究发现,小麦和玉米基础饲粮中分别添加木聚糖酶均可显著降低肉鸡空肠食糜黏度(玉米:3.72 mPa·s vs. 2.37 mPa·s;小麦:5.22 mPa·s vs. 2.22 mPa·s)。

2.2 降解植物细胞壁

水不溶性木聚糖可将养分包裹在植物细胞壁内,阻碍机体对这部分养分的利用,即“笼蔽效应”[1]。Khadem等[33]以非黏性谷物-玉米为基础饲粮,以排除饲料原料对消化道食糜黏性的影响,并在肉鸡基础饲粮中添加木聚糖酶,与通过冻融处理从而解除“笼蔽效应”的玉米基础饲粮的饲喂效果进行比较,结果表明,木聚糖酶可以通过消除植物细胞壁的屏障作用,促进肉鸡对养分高效的消化吸收。

2.3 提供益生元

研究表明,木聚糖酶可将阿拉伯木聚糖水解成低聚木糖,而低聚木糖近年来被认为可类似于益生元发挥作用,有益于双歧杆菌和乳酸杆菌等健康菌群的定植,以及减少病原菌丰度,从而改善肠道菌群结构[34]。Morgan等[35]通过体外和体内试验探究木聚糖酶对阿拉伯木聚糖的水解效果,结果表明,添加木聚糖酶可显著提高肉鸡小肠中木糖和低聚木糖含量,在低聚木糖中,木五糖含量最高,木四糖、木三糖和木二糖含量次之,木糖含量最低。Dale等[36]研究发现,小麦基础饲粮中添加木聚糖酶可显著提高肉鸡结肠中木四糖含量以及结肠和盲肠中木糖含量,低聚木糖含量的增加又可进一步提高后肠道乙酸含量,进而改善肠道健康。

3 木聚糖酶对肉鸡生长性能和养分消化率的影响

木聚糖酶对肉鸡生长性能的改善作用目前已被广泛报道(表 2)。Gonzalez-Ortiz等[45]研究发现,小麦-豆粕基础饲粮中添加木聚糖酶可改善1~21日龄肉鸡的平均日增重和饲料转化率。徐叶桐等[48]研究结果表明,小麦基础饲粮中添加木聚糖酶可改善22~42日龄肉鸡的饲料转化率。黑麦-小麦-玉米-豆粕基础饲粮中添加木聚糖酶同样可改善1~42日龄肉鸡的饲料转化率[40]。Zhang等[47]研究发现,小麦-豆粕基础饲粮中添加木聚糖酶可显著增加肉鸡蛋白质、淀粉、可溶性NSP和非可溶性NSP的回肠表观消化率,以及干物质、蛋白质、淀粉和可溶性NSP的全肠道表观消化率。Choct等[49]同样发现,小麦基础饲粮中添加木聚糖酶可显著增加非可溶性NSP的回肠表观消化率。

表 2 木聚糖酶对肉鸡生长性能的影响 Table 2 Effects of xylanases on growth performance of broilers

当肉鸡饲喂玉米基础饲粮时,虽相较于小麦、黑麦和燕麦等作物,玉米中水溶性木聚糖含量较低,肠道食糜黏度不是主要的抗营养因素,但人们认为木聚糖酶可高效降解玉米中所含的水不溶性木聚糖,促进植物细胞壁中营养物质的释放和水解,所产生的低聚木糖具有益生作用[50]。Zhang等[41]研究发现,玉米-豆粕基础饲粮中添加木聚糖酶可改善1~42日龄肉鸡的饲料转化率。Amerah等[44]研究发现,玉米-豆粕基础饲粮中添加木聚糖酶可显著增加肉鸡的氮校正表观代谢能。Stefanello等[51]研究发现,玉米-豆粕基础饲粮中添加木聚糖酶可显著增加肉鸡回肠可消化能、氮校正表观代谢能以及干物质和蛋白质沉积率。

4 木聚糖酶对肉鸡肠道健康的影响 4.1 木聚糖酶对肉鸡肠道消化生理的影响

内源性消化酶对于养分的消化至关重要,根据“笼蔽效应”假说,木聚糖酶可在肉鸡体内表现出明显的细胞壁破坏效应,这可有效增加消化酶对细胞内容物的接触,从而增强内源性消化酶的功效[28]。Guo等[52]研究发现,小麦基础饲粮中添加木聚糖酶可显著提高21日龄肉鸡胰腺糜蛋白酶活性,胰腺糜蛋白酶活性的增加可能由于补充NSP酶打破细胞壁,释放更多的可消化蛋白质。Engberg等[53]同样发现,小麦基础饲粮中添加木聚糖酶可改善胰腺脂肪酶和糜蛋白酶活性。但也有部分报道表明,饲粮添加木聚糖酶对肉鸡消化道内源酶活性影响不显著。Luo等[28]研究结果表明,小麦基础饲粮中添加木聚糖酶对42日龄肉鸡十二指肠、空肠和回肠的淀粉酶和蛋白酶活性没有显著影响。Liu等[46]研究结果同样表明,饲粮添加木聚糖酶对35日龄肉鸡小肠胰蛋白酶、糜蛋白酶和淀粉酶活性没有显著影响。Almirall等[54]研究发现,饲粮添加NSP酶可增加幼龄肉鸡小肠淀粉酶活性,然而研究中未观察到其对成年肉鸡消化道内源酶活性的影响。同时,本课题组前期研究发现小麦基础饲粮中添加木聚糖酶可显著提高7和21日龄肉鸡胰腺糜蛋白酶和脂肪酶活性,然而对42日龄肉鸡胰腺消化酶活性并无显著影响。因此我们推测,相较于幼龄肉鸡,成年肉鸡消化系统发育较为成熟,具有较强的耐受性,NSP对其负面影响较小。

小肠黏膜二糖酶对养分的消化吸收以及能量的转化利用同样具有重要意义。Guo等[52]研究表明,小麦基础饲粮中添加木聚糖酶可显著增加21日龄肉鸡空肠蔗糖酶活性。黄婧溪等[55]研究也表明,小麦-豆粕基础饲粮中添加木聚糖酶可改善肉鸡十二指肠麦芽糖酶活性以及空肠麦芽糖酶和蔗糖酶活性。通常,小麦中的阿拉伯木聚糖可使肠道食糜黏度增加,阻碍小肠刷状缘酶与底物接触,而添加木聚糖酶可降低肠道食糜黏度,使二糖酶更易到达水解位点与底物接触,从而通过反馈调节的方式进一步诱导二糖酶的分泌。同时,木聚糖酶降解小麦中的阿拉伯木聚糖,也可为二糖酶提供更多的底物发挥作用[52, 55]

小肠刷状缘黏膜上的营养物质转运蛋白对于机体的养分吸收也尤为重要。钠-葡萄糖共转运载体1(sodium-glucose cotransporter,SGLT1)介导小肠黏膜对葡萄糖和半乳糖的钠依赖性摄取,寡肽转运蛋白1(peptide transporter 1,PepT1)负责将二肽和三肽运输至上皮细胞,肝脏脂肪酸结合蛋白(liver fatty acid-binding protein,L-FABP)则在脂质代谢和转运中发挥重要作用[56]。王修启等[57]研究表明,小麦基础饲粮中添加木聚糖酶可提高30日龄肉鸡十二指肠(33.30%)和空肠SGLT1 mRNA表达水平(8.21%)。Guo等[52]研究表明,产气荚膜梭菌的感染降低了肉鸡空肠SGLT1、PepT1和L-FABP mRNA表达水平,然而添加木聚糖酶可使受产气荚膜梭菌感染的肉鸡相关基因表达水平提高至与对照组相同甚至更高的水平。因此,木聚糖酶可能通过作用于小肠上段,从而上调养分转运蛋白的表达水平,促进肉鸡对养分的消化吸收。

4.2 木聚糖酶对肉鸡肠道发育及形态的影响

目前已有研究发现,空肠食糜黏度的增加可引起肠道总重量和总长度的增加,尤其在非常高的黏度条件下,肠道的重量可呈现成倍增加[58]。Engberg等[53]研究发现,小麦基础饲粮中添加木聚糖酶可显著降低空肠和回肠的相对重量。Wu等[59]同样发现,小麦基础饲粮中添加木聚糖酶可显著降低十二指肠(17.8%)、空肠(15.8%)、回肠(14.6%)以及小肠(15.5%)的相对重量。然而,部分研究观察到,木聚糖酶对肉鸡的十二指肠、空肠、回肠和小肠的相对重量并没有显著影响[60-61]。崔朝霞[62]研究发现,河套小麦饲粮添加木聚糖酶后,肉鸡的十二指肠相对重量显著减少;然而北京小麦饲粮添加木聚糖酶后,肉鸡的十二指肠相对重量虽减少,但差异不显著;已知河套小麦提取液的黏度比北京小麦高,因此当消化道食糜黏度较低时,木聚糖酶对于肠道重量可能影响较小。此外,Gonzalez-Ortiz等[43]研究发现,小麦基础饲粮中添加木聚糖酶可增加42日龄肉鸡的回肠相对重量和十二指肠长度,消化器官重量的提高可在一定程度说明机体具有较好的消化能力,同时也可阻止一些有害微生物的定植。因此,木聚糖酶对于肠道重量的影响可能与底物的类型和浓度以及酶的性质和添加水平等多个因素有关,具体机理仍有待于进一步研究。

肠道形态结构对于小肠功能的发挥具有重要意义。Wu等[60]研究表明,小麦基础饲粮中添加木聚糖酶可显著增加肉鸡回肠绒毛高度。Luo等[28]研究发现,木聚糖酶可显著增加21日龄肉鸡十二指肠、空肠和回肠的绒毛高度以及绒毛高度与隐窝深度的比值。木聚糖通常可使消化道食糜黏度增加,抑制绒毛与养分之间的有效接触,导致肠黏膜结构和功能的退化和减弱,而木聚糖酶可通过降低消化道食糜的黏度来缓解NSP对肠道形态的负面影响[28, 60]

4.3 木聚糖酶对肉鸡肠道菌群的影响

木聚糖可使肉鸡消化道食糜黏度增加,肠道活动性降低,这将降低氧张力,并促进影响肠道组织生长的病原微生物定植[31]。已有研究表明,饲粮中含有大量的水溶性NSP可导致肉鸡小肠的肠杆菌丰度增加[63]。而补充木聚糖酶可加速机体对养分的消化吸收和利用,这可能减少回肠微生物可用的底物,从而降低微生物活性[31]。Bedford等[64]研究发现,小麦基础饲粮中添加木聚糖酶可使肉鸡肠道菌群数量减少60%。郭双双[56]研究发现,饲粮添加木聚糖酶可表现出降低肉鸡回肠Shannon多样性指数的趋势。任何潜在的回肠发酵的减少可能都是有益的,因为在该区域发酵的底物主要是未消化或者被包裹的淀粉和蛋白质等养分,而这些养分本应被肉鸡消化吸收利用的。此外,饲粮添加木聚糖酶可促进小肠中乳酸杆菌的定植,而乳酸杆菌可有效抑制致病菌群在肠道中的定植[53]

木聚糖的水解产物低聚木糖可作为益生元,增加双歧杆菌和乳酸杆菌等改善肠道健康的细菌丰度,同时可通过刺激后肠道中乳酸杆菌的生长来间接抑制某些致病菌的定植[36, 65]。Lee等[66]研究表明,木聚糖酶组的42日龄肉鸡盲肠双歧杆菌丰度显著高于对照组。Nian等[67]同样发现,饲粮添加木聚糖酶可促进盲肠乳酸杆菌和双歧杆菌的定植。Melo-Durán等[68]研究发现,玉米基础饲粮中添加木聚糖酶显著增加毛螺菌科丰度,毛螺菌科通常被认作是丁酸产生菌。同时,部分报道说明,小麦基础饲粮添加木聚糖酶可显著降低肉鸡盲肠产气荚膜梭菌丰度[69]

4.4 木聚糖酶对肉鸡肠道微生物代谢产物的影响

肉鸡肠道中挥发性脂肪酸和乳酸浓度可在一定程度反映肠道微生物活性。高黏度的小肠食糜会减缓消化道内容物的流动速度,从而改变微生物平衡,降低肠道张力,促进菌群发酵,肉鸡小肠的过度发酵可能不利于养分的消化吸收,然而添加木聚糖酶可降低食糜黏度,减少底物和微生物作用的时间,从而缓解小肠的过度发酵[31]。Jozefiak等[70]研究发现,黑麦基础饲粮中添加木聚糖酶可显著降低肉鸡回肠乳酸和总挥发性脂肪酸浓度。然而,Engberg等[53]研究结果表明,饲粮添加木聚糖可增加小肠乳酸杆菌丰度,进而提高乳酸浓度,但小肠中其他挥发性脂肪酸(特别是乙酸)浓度并不受木聚糖酶的影响。因此,木聚糖酶对于回肠乳酸和挥发性脂肪酸浓度的影响仍有待于进一步研究。

目前,人们广泛认为木聚糖的水解产物如低聚木糖可进入盲肠,由微生物发酵成为有益的挥发性脂肪酸,尤其是丁酸和乙酸[31, 68]。其中,丁酸可增强上皮细胞的吸收能力,同时可调节黏蛋白的产生,参与免疫过程,并下调肠道病原菌群的定植[71-72]。高浓度的挥发性脂肪酸可降低盲肠pH,从而阻止致病微生物菌群的定植,盲肠的微生物发酵不会造成养分的损失,但可提供额外的能量供宿主利用[71]。Engberg等[53]研究发现,小麦-豆粕基础饲粮中添加木聚糖酶显著降低肉鸡的盲肠pH。Kubi s ′等[73]研究发现,小麦-豆粕基础饲粮中添加木聚糖酶同样降低肉鸡盲肠pH,并显著增加盲肠乙酸和丁酸浓度。Masey-O’neill等[50]则研究发现,玉米-豆粕基础饲粮中添加木聚糖酶显著增加盲肠丙酸浓度;而小麦-豆粕基础饲粮中添加木聚糖酶可显著增加己酸浓度。Lee等[66]研究表明,饲粮添加木聚糖酶可显著增加42日龄肉鸡盲肠双歧杆菌丰度,双歧杆菌可在肠道内发酵产生乳酸和丁酸。然而,乳酸很可能被利用乳酸的细菌转化为丁酸或者其他挥发性脂肪酸。因此研究中观察到,饲粮添加木聚糖酶可显著提高乙酸和丁酸浓度,以及降低乳酸浓度。还有研究表明,饲粮添加木聚糖酶对于肉鸡盲肠挥发性脂肪酸浓度并没有显著影响[70, 74]。实际上,盲肠中挥发性脂肪酸浓度并不一定能准确反映细菌产生挥发性脂肪酸的速率。这可能由于后肠段产生的95%~99%的挥发性脂肪酸被吸收,挥发性脂肪酸从肠道进入血液的速度极快[75]。此外,消化道内容物的流动是动态的,反向蠕动可能导致挥发性脂肪酸局部浓度变化[76]

4.5 木聚糖酶对肉鸡肠道免疫功能的影响

肠道食糜黏度的增加对机体肠道生理和微生物群落产生不利影响,并可间接影响肠道免疫功能[77]。Wang等[78]研究结果表明,饲粮添加木聚糖酶和甘露聚糖酶可显著增加肉鸡空肠闭合蛋白-1(claudin-1)mRNA表达水平,claudin-1对于维持肠道黏膜屏障功能具有重要作用。同时,饲粮添加木聚糖酶和甘露聚糖酶可增加空肠白细胞介素-10(IL-10)含量,减少肿瘤坏死因子-α(TNF-α)和白细胞介素-1β(IL-1β)含量。郭双双[56]研究发现,饲粮添加木聚糖酶显著增加回肠咬合蛋白(occludin)和claudin-1 mRNA表达水平。同时,饲粮添加木聚糖酶显著下调十二指肠白细胞介素-1(IL-1)mRNA表达水平。综上所述,木聚糖酶可激活免疫反应以防止病原体入侵,从而通过促炎和抗炎反应之间的平衡来维持肠道稳态。

5 当前存在的问题及未来发展趋势

在饲料工业中,一方面,考虑到动物胃肠道环境pH和饲用木聚糖酶通常需在酸性至中性的环境中保持较高的活力;另一方面,饲料在制粒加工过程中有一个短暂升温过程,木聚糖酶在此高温条件下可能会大幅度丧失活力;因此,饲用木聚糖酶必须具有良好的抗酸性和热稳定性[79]。此外,木聚糖酶对胃肠道蛋白酶的抗性,也是木聚糖酶在饲料工业中应用时的重要考虑因素[79]。目前,应用于肉鸡饲养的大部分木聚糖酶的活性虽已报道,但很少有人报道相关饲用木聚糖酶在酸性和高温环境的酶活性损失,以及木聚糖酶对胃和胰蛋白酶的耐受性,对木聚糖酶的特性进行全面了解更有利于木聚糖酶的高效应用。耐酸、耐热以及耐蛋白酶是木聚糖酶可在肉鸡体内有效发挥作用、降解阿拉伯木聚糖的保证,而这也对指导木聚糖酶的产品开发及应用具有重要意义。

虽然大量研究已表明,木聚糖酶可有效改善肉鸡生长性能,然而实际上肉鸡日龄和饲粮类型很大程度影响木聚糖酶作用的发挥。研究证明,饲喂小麦基础饲粮的肉鸡,消化道食糜黏度随着肉鸡日龄增长而降低[80]。由于肉鸡自身不能产生和分泌木聚糖酶,通常依赖其肠道微生物来降解阿拉伯木聚糖,而胃肠道微生物降解阿拉伯木聚糖的能力,通常随着肉鸡日龄的增加而变化。Bautil等[81]研究结果表明,随着肉鸡日龄的增加,肠道微生物逐渐发育成熟,回肠、盲肠以及全肠道阿拉伯木聚糖消化率逐渐增加。因此,特定阶段微生物群可能对胃肠道中的阿拉伯木聚糖存在适应性反应,而这种适应性表明添加木聚糖酶的益处可能随着肉鸡日龄的增加而改变。目前,关于木聚糖酶对于不同阶段肉鸡生长性能影响并不一致,一些研究表明,木聚糖酶的添加主要对肉鸡早期生长性能影响更为显著[82]。这些研究普遍认为,在高含量可溶性NSP的高黏度饲粮中,添加NSP酶可显著降低消化道食糜黏度,从而改善肉鸡生长性能。幼龄肉鸡的消化道食糜黏度最高,饲粮中添加NSP酶对肉鸡的积极影响,可在肉鸡生长的第1周就观察到[83]。然而,一些研究结果表明,由于饲粮中可溶性木聚糖含量相对较低,因此对消化道食糜黏度影响较小,而木聚糖酶对于饲喂低黏度饲粮肉鸡生长性能的改善被认为可能主要由盲肠微生物介导;定植在肉鸡盲肠的微生物群落在2~3周龄时才逐渐发育成熟,因此木聚糖酶对于肉鸡生长性能的改善主要在肉鸡生长后期观察到的[84-85]。Bedford[86]提出一种新的假设,随着时间的推移,饲粮添加木聚糖酶可以“训练”肉鸡的肠道微生物群落,提高其降解纤维源的能力。已有研究证明,饲喂阿拉伯低聚木糖可提高肉鸡肠道微生物降解木聚糖的能力,低聚木糖对微生物纤维降解能力表现出明显的刺激作用,使肠道微生物得到某种程度的“训练”或进化[87]。综上所述,由于肉鸡日龄和饲粮类型的不同会相应使得木聚糖酶在应用时的效果表现出不一致性,尽管部分研究已经提出这种不一致性,但仍缺少系统的研究。木聚糖酶在肉鸡肠道内的有益作用主要包括3种,然而实际上可能需要根据饲粮类型和肉鸡日龄重新进行评估和检验,尤其是阿拉伯木聚糖降解所产生低聚木糖的益生作用,随着色谱分析方法的发展,被认为可更好地探究其机理,而这有利于木聚糖酶在肉鸡上的应用得到进一步改进和优化。

6 小结

饲粮添加木聚糖酶可有效水解木聚糖,降低食糜黏度,破坏植物细胞壁,提供益生元,进而改善肉鸡肠道健康。然而,木聚糖酶对于肉鸡肠道健康影响相关研究仍表现出部分的不一致性,其结果可能与肉鸡日龄、饲粮类型、酶学性质等多方面因素有关。因此,应进一步探索木聚糖酶对不同日龄肉鸡肠道健康的作用效果,木聚糖酶添加于不同类型饲粮中对肉鸡肠道健康的影响,以及开发耐酸、耐热和抗蛋白酶的木聚糖酶,最终实现木聚糖酶在家禽养殖业中的高效应用。

参考文献
[1]
RAZA A, BASHIR S, TABASSUM R. An update on carbohydrases: growth performance and intestinal health of poultry[J]. Heliyon, 2019, 5(4): e01437. DOI:10.1016/j.heliyon.2019.e01437
[2]
高俊勤. 木聚糖酶对肉仔鸡肠道消化特性及微生物区系的影响[D]. 硕士学位论文. 南京: 南京农业大学, 2007.
GAO J Q. The effects of xylanase on the nutrient digestibility and microflora of the gastrointestinal tract of broiler chickens[D]. Master's Thesis. Nanjing: Nanjing Agricultural University, 2007. (in Chinese)
[3]
尚庆辉, 朴香淑, 王玉磷. 木聚糖酶在畜禽饲料中应用效果及其机理的研究进展[J]. 饲料工业, 2017, 38(2): 17-24.
SHANG Q H, PIAO X S, WANG Y L. Application effects and mechanism of xylanase in animal feed[J]. Feed Industry, 2017, 38(2): 17-24 (in Chinese).
[4]
TELLEZ G, LATORRE J D, KUTTAPPAN V A, et al. Utilization of rye as energy source affects bacterial translocation, intestinal viscosity, microbiota composition, and bone mineralization in broiler chickens[J]. Frontiers in Genetics, 2014, 5: 339.
[5]
XING H G, ZOU G, LIU C Y, et al. Improving the thermostability of a GH11 xylanase by directed evolution and rational design guided by B-factor analysis[J]. Enzyme and Microbial Technology, 2021, 143: 109720. DOI:10.1016/j.enzmictec.2020.109720
[6]
ABD EL-WAHAB A, LINGENS J B, CHUPPAVA B, et al. Impact of rye inclusion in diets for broilers on performance, litter quality, foot pad health, digesta viscosity, organ traits and intestinal morphology[J]. Sustainability, 2020, 12(18): 7753. DOI:10.3390/su12187753
[7]
QESHMI F I, HOMAEI A, FERNANDES P, et al. Xylanases from marine microorganisms: a brief overview on scope, sources, features and potential applications[J]. Biochimica et Biophysica Acta: Proteins and Proteomics, 2020, 1862(2): 140312.
[8]
UDAY U S P, CHOUDHURY P, BANDYOPADHYAY T K, et al. Classification, mode of action and production strategy of xylanase and its application for biofuel production from water hyacinth[J]. International Journal of Biological Macromolecules, 2016, 82: 1041-1054. DOI:10.1016/j.ijbiomac.2015.10.086
[9]
JUTURU V, WU J C. Microbial xylanases: engineering, production and industrial applications[J]. Biotechnology Advances, 2012, 30(6): 1219-1227. DOI:10.1016/j.biotechadv.2011.11.006
[10]
杨雯涵. 硫色曲霉酸性木聚糖酶耐热性改造研究[D]. 硕士学位论文. 北京: 中国农业大学, 2015.
YANG W H. Study on heat resistant modification of Aspergillus sulphureus acidic xylanase[D]. Master's Thesis. Beijing: China Agricultural University, 2015. (in Chinese)
[11]
BHARDWAJ N, KUMAR B, VERMA P. A detailed overview of xylanases: an emerging biomolecule for current and future prospective[J]. Bioresources and Bioprocessing, 2019, 6: 40. DOI:10.1186/s40643-019-0276-2
[12]
SALEEM A, WARIS S, AHMED T, et al. Biochemical characterization and molecular docking of cloned xylanase gene from Bacillus subtilis RTS expressed in E. coli[J]. International Journal of Biological Macromolecules, 2021, 168: 310-321. DOI:10.1016/j.ijbiomac.2020.12.001
[13]
LAI Z H, ZHOU C, MA X C, et al. Enzymatic characterization of a novel thermostable and alkaline tolerant GH10 xylanase and activity improvement by multiple rational mutagenesis strategies[J]. International Journal of Biological Macromolecules, 2020, 170: 164-177.
[14]
WANG K, CAO R T, WANG M L, et al. A novel thermostable GH10 xylanase with activities on a wide variety of cellulosic substrates from a xylanolytic Bacillus strain exhibiting significant synergy with commercial celluclast 1.5 L in pretreated corn stover hydrolysis[J]. Biotechnology for Biofuels, 2019, 12: 48. DOI:10.1186/s13068-019-1389-8
[15]
KUMAR V, SATYANARAYANA T. Production of endoxylanase with enhanced thermostability by a novel polyextremophilic Bacillus halodurans TSEV1 and its applicability in waste paper deinking[J]. Process Biochemistry, 2014, 49(3): 386-394. DOI:10.1016/j.procbio.2013.12.005
[16]
SUKHUMSIRICHART M, DEESUKON W, KAWAKAMI T, et al. Expression and characterization of recombinant GH11 xylanase from thermotolerant Streptomyces sp. SWU10[J]. Applied Biochemistry and Biotechnology, 2014, 172(1): 436-446. DOI:10.1007/s12010-013-0508-4
[17]
JIANG X B, LIN J C, LIANG S Z, et al. High-efficient expression and pilot scale fermentation of Streptomyces xylanase from a constitutive Pichia pastoris vector[J]. Food Biotechnology, 2013, 27(1): 54-65. DOI:10.1080/08905436.2012.755693
[18]
MHIRI S, BOUANANE-DARENFED A, JEMLI S, et al. A thermophilic and thermostable xylanase from Caldicoprobacter algeriensis: recombinant expression, characterization and application in paper biobleaching[J]. International Journal of Biological Macromolecules, 2020, 164: 808-817. DOI:10.1016/j.ijbiomac.2020.07.162
[19]
YU J, LIU X Q, GUAN L Y, et al. High-level expression and enzymatic properties of a novel thermostable xylanase with high arabinoxylan degradation ability from Chaetomium sp. suitable for beer mashing[J]. International Journal of Biological Macromolecules, 2021, 168: 223-232. DOI:10.1016/j.ijbiomac.2020.12.040
[20]
ZHAO L, MENG K, BAI Y G, et al. Two family 11 xylanases from Achaetomium sp. Xz-8 with high catalytic efficiency and application potentials in the brewing industry[J]. Journal of Agricultural and Food Chemistry, 2013, 61(28): 6880-6889. DOI:10.1021/jf4001296
[21]
OUEPHANIT C, BOONVITTHYA N, BOZONNET S, et al. High-level heterologous expression of endo-1, 4-β-xylanase from Penicillium citrinum in Pichia pastoris X-33 directed through codon optimization and optimized expression[J]. Molecules, 2019, 24(19): 3515. DOI:10.3390/molecules24193515
[22]
GIL-DURÁN C, RAVANAL M C, UBILLA P, et al. Heterologous expression, purification and characterization of a highly thermolabile endoxylanase from the Antarctic fungus Cladosporium sp.[J]. Fungal Biology, 2018, 122(9): 875-882. DOI:10.1016/j.funbio.2018.05.002
[23]
HUANG Y H, ZHENG X L, PILGAARD B, et al. Identification and characterization of GH11 xylanase and GH43 xylosidase from the chytridiomycetous fungus, Rhizophlyctis rosea[J]. Applied Microbiology and Biotechnology, 2019, 103(2): 777-791. DOI:10.1007/s00253-018-9431-5
[24]
WANG X Y, MA R, XIE X M, et al. Thermostability improvement of a Talaromyces leycettanus xylanase by rational protein engineering[J]. Scientific Reports, 2017, 7: 15287. DOI:10.1038/s41598-017-12659-y
[25]
BHARDWAJ N, KUMAR N, AGARWAL K, et al. Purification and characterization of a thermo-acid/alkali stable xylanases from Aspergillus oryzae LC1 and its application in xylo-oligosaccharides production from lignocellulosic agricultural wastes[J]. International Journal of Biological Macromolecules, 2019, 122: 1191-1202. DOI:10.1016/j.ijbiomac.2018.09.070
[26]
CHADHA B S, KAUR B, BASOTRA N, et al. Thermostable xylanases from thermophilic fungi and bacteria: current perspective[J]. Bioresource Technology, 2019, 277: 195-203. DOI:10.1016/j.biortech.2019.01.044
[27]
CHAKDAR H, KUMAR M, PANDIYAN K, et al. Bacterial xylanases: biology to biotechnology[J]. 3 Biotech, 2016, 6(2): 150. DOI:10.1007/s13205-016-0457-z
[28]
LUO D Y, YANG F X, YANG X J, et al. Effects of xylanase on performance, blood parameters, intestinal morphology, microflora and digestive enzyme activities of broilers fed wheat-based diets[J]. Asian-Australasian Journal of Animal Sciences, 2009, 22(9): 1288-1295. DOI:10.5713/ajas.2009.90052
[29]
HEDEMANN M S, THEIL P K, KNUDSEN K E B. The thickness of the intestinal mucous layer in the colon of rats fed various sources of non-digestible carbohydrates is positively correlated with the pool of SCFA but negatively correlated with the proportion of butyric acid in digesta[J]. British Journal of Nutrition, 2009, 102(1): 117-125. DOI:10.1017/S0007114508143549
[30]
RAVN J L, MARTENS H J, PETTERSSON D, et al. A commercial GH 11 xylanase mediates xylan solubilisation and degradation in wheat, rye and barley as demonstrated by microscopy techniques and wet chemistry methods[J]. Animal Feed Science and Technology, 2016, 219: 216-225. DOI:10.1016/j.anifeedsci.2016.06.020
[31]
CHOCT M, HUGHES R J, BEDFORD M R. Effects of a xylanase on individual bird variation, starch digestion throughout the intestine, and ileal and caecal volatile fatty acid production in chickens fed wheat[J]. British Poultry Science, 1999, 40(3): 419-422. DOI:10.1080/00071669987548
[32]
KIARIE E, ROMERO L F, RAVINDRAN V. Growth performance, nutrient utilization, and digesta characteristics in broiler chickens fed corn or wheat diets without or with supplemental xylanase[J]. Poultry Science, 2014, 93(5): 1186-1196. DOI:10.3382/ps.2013-03715
[33]
KHADEM A, LOURENCO M, DELEZIE E, et al. Does release of encapsulated nutrients have an important role in the efficacy of xylanase in broilers?[J]. Poultry Science, 2016, 95(5): 1066-1076. DOI:10.3382/ps/pew002
[34]
KARLSSON E N, SCHMITZ E, LINARES-PASTÉN J A, et al. Endo-xylanases as tools for production of substituted xylooligosaccharides with prebiotic properties[J]. Applied Microbiology and Biotechnology, 2018, 102(21): 9081-9088. DOI:10.1007/s00253-018-9343-4
[35]
MORGAN N K, WALLACE A, BEDFORD M R, et al. In vitro versus in situ evaluation of xylan hydrolysis into xylo-oligosaccharides in broiler chicken gastrointestinal tract[J]. Carbohydrate Polymers, 2020, 230: 115645. DOI:10.1016/j.carbpol.2019.115645
[36]
DALE T, HANNAY I, BEDFORD M R, et al. The effects of exogenous xylanase supplementation on the in vivo generation of xylooligosaccharides and monosaccharides in broilers fed a wheat-based diet[J]. British Poultry Science, 2020, 61(4): 471-481. DOI:10.1080/00071668.2020.1751805
[37]
CRAIG A D, KHATTAK F, HASTIE P, et al. Xylanase and xylo-oligosaccharide prebiotic improve the growth performance and concentration of potentially prebiotic oligosaccharides in the ileum of broiler chickens[J]. British Poultry Science, 2020, 61(1): 70-78. DOI:10.1080/00071668.2019.1673318
[38]
LEE S H, HOSSEINDOUST A, INGALE S L, et al. Thermostable xylanase derived from Trichoderma citrinoviride increases growth performance and non-starch polysaccharide degradation in broiler chickens[J]. British Poultry Science, 2020, 61(1): 57-62. DOI:10.1080/00071668.2019.1673316
[39]
HU H, DAI S F, WEN A Y, et al. Efficient expression of xylanase by codon optimization and its effects on the growth performance and carcass characteristics of broiler[J]. Animals, 2019, 9(2): 65. DOI:10.3390/ani9020065
[40]
ARCZEWSKA-WLOSEK A, SWIATKIEWICZ S, BEDERSKA-LOJEWSKA D, et al. The efficiency of xylanase in broiler chickens fed with increasing dietary levels of rye[J]. Animals, 2019, 9(2): 46. DOI:10.3390/ani9020046
[41]
ZHANG S T, WANG C F, SUN Y, et al. Xylanase and fermented polysaccharide of Hericium caputmedusae reduce pathogenic infection of broilers by improving antioxidant and anti-inflammatory properties[J]. Oxidative Medicine and Cellular Longevity, 2018, 2018: 4296985.
[42]
NOURMOHAMMADI R, KHOSRAVINIA H, AFZALI N. Effects of feed form and xylanase supplementation on metabolizable energy partitioning in broiler chicken fed wheat-based diets[J]. Journal of Animal Physiology and Animal Nutrition, 2018, 102(6): 1593-1600. DOI:10.1111/jpn.12980
[43]
GONZALEZ-ORTIZ G, SOLA-ORIOL D, MARTINEZ-MORA M, et al. Response of broiler chickens fed wheat-based diets to xylanase supplementation[J]. Poultry Science, 2017, 96(8): 2776-2785. DOI:10.3382/ps/pex092
[44]
AMERAH A M, ROMERO L F, AWATI A, et al. Effect of exogenous xylanase, amylase, and protease as single or combined activities on nutrient digestibility and growth performance of broilers fed corn/soy diets[J]. Poultry Science, 2017, 96(4): 807-816. DOI:10.3382/ps/pew297
[45]
GONZÁLEZ-ORTIZ G, OLUKOSI O, BEDFORD M R. Evaluation of the effect of different wheats and xylanase supplementation on performance, nutrient and energy utilisation in broiler chicks[J]. Animal Nutrition, 2016, 2(3): 173-179. DOI:10.1016/j.aninu.2016.06.005
[46]
LIU W C, KIM I H. Effects of dietary xylanase supplementation on performance and functional digestive parameters in broilers fed wheat-based diets[J]. Poultry Science, 2017, 96(3): 566-573. DOI:10.3382/ps/pew258
[47]
ZHANG L, XU L, LEI L, et al. Effects of xylanase supplementation on growth performance, nutrient digestibility and non-starch polysaccharide degradation in different sections of the gastrointestinal tract of broilers fed wheat-based diets[J]. Asian-Australasian Journal of Animal Sciences, 2014, 27(6): 855-861. DOI:10.5713/ajas.2014.14006
[48]
徐叶桐, 曾志凯, 何政肖, 等. 木聚糖酶对小麦型基础日粮肉仔鸡生长和消化率的影响[J]. 饲料研究, 2017(7): 1-4, 11.
XU Y T, ZENG Z K, HE Z X, et al. Effects of xylanase on growth performance and nutrient digestibility of broilers fed wheat-based diets[J]. Feed Research, 2017(7): 1-4, 11 (in Chinese).
[49]
CHOCT M, KOCHER A, WATERS D L E, et al. A comparison of three xylanases on the nutritive value of two wheats for broiler chickens[J]. British Journal of Nutrition, 2004, 92(1): 53-61. DOI:10.1079/BJN20041166
[50]
MASEY-O'NEILL H V, SINGH M, COWIESON A J. Effects of exogenous xylanase on performance, nutrient digestibility, volatile fatty acid production and digestive tract thermal profiles of broilers fed on wheat- or maize-based diet[J]. British Poultry Science, 2014, 55(3): 351-359. DOI:10.1080/00071668.2014.898836
[51]
STEFANELLO C, VIEIRA S L, CARVALHO P S, et al. Energy and nutrient utilization of broiler chickens fed corn-soybean meal and corn-based diets supplemented with xylanase[J]. Poultry Science, 2016, 95(8): 1881-1887. DOI:10.3382/ps/pew070
[52]
GUO S S, LIU D, ZHAO X, et al. Xylanase supplementation of a wheat-based diet improved nutrient digestion and mRNA expression of intestinal nutrient transporters in broiler chickens infected with Clostridium perfringens[J]. Poultry Science, 2014, 93(1): 94-103. DOI:10.3382/ps.2013-03188
[53]
ENGBERG R M, HEDEMANN M S, STEENFELDT S, et al. Influence of whole wheat and xylanase on broiler performance and microbial composition and activity in the digestive tract[J]. Poultry Science, 2004, 83(6): 925-938. DOI:10.1093/ps/83.6.925
[54]
ALMIRALL M, FRANCESCH M, PEREZ-VENDRELL A M, et al. The differences in intestinal viscosity produced by barley and β-glucanase alter digesta enzyme activities and ileal nutrient digestibilities more in broiler chicks than in cocks[J]. The Journal of Nutrition, 1995, 125(4): 947-955.
[55]
黄婧溪, 黄忠良, 臧旭鹏, 等. 不同来源木聚糖酶及其组合对肉鸡肠道黏膜形态与二糖酶活性及其基因表达的影响[J]. 动物营养学报, 2018, 30(6): 2271-2280.
HUANG J X, LI Z L, ZANG X P, et al. Effects of different sources of xylanase and their combination on intestinal morphology, disaccharidase activities and gene expression of broilers[J]. Chinese Journal of Animal Nutrition, 2018, 30(6): 2271-2280 (in Chinese). DOI:10.3969/j.issn.1006-267x.2018.06.031
[56]
郭双双. 木聚糖酶与益生菌缓解肠道炎症的作用及其机制[D]. 博士学位论文. 北京: 中国农业大学, 2016.
GUO S S, The attenuate effects of xylanase and probiotics on the intestinal inflammation and the related mechanisms[D]. Ph. D. Thesis. Beijing: China Agricultural University, 2016. (in Chinese)
[57]
王修启, 张兆敏, 张磊, 等. 日粮添加木聚糖酶对肉鸡小肠葡萄糖吸收及其转运载体基因表达影响[J]. 农业生物技术学报, 2005, 13(4): 497-502.
WANG X Q, ZHANG Z M, ZHANG L, et al. Dietary xylanase supplementation affects glucose absorption and SGLT1 mRNA expression in intestine of broiler chickens fed wheat-based diets[J]. Journal of Agricultural Biotechnology, 2005, 13(4): 497-502 (in Chinese). DOI:10.3969/j.issn.1674-7968.2005.04.018
[58]
SIMON O. The mode of action of NSP hydrolysing enzymes in the gastrointestinal tract[J]. Journal of Animal and Feed Sciences, 1998, 7(Suppl.1): 115-123.
[59]
WU Y B, RAVINDRAN V, THOMAS D G, et al. Influence of phytase and xylanase, individually or in combination, on performance, apparent metabolisable energy, digestive tract measurements and gut morphology in broilers fed wheat-based diets containing adequate level of phosphorus[J]. British Poultry Science, 2004, 45(1): 76-84. DOI:10.1080/00071660410001668897
[60]
WU Y B, RAVINDRAN V, THOMAS D G, et al. Influence of method of whole wheat inclusion and xylanase supplementation on the performance, apparent metabolisable energy, digestive tract measurements and gut morphology of broilers[J]. British Poultry Science, 2004, 45(3): 385-394. DOI:10.1080/00071660410001730888
[61]
BRENES A, SMITH M, GUENTER W, et al. Effect of enzyme supplementation on the performance and digestive tract size of broiler chickens fed wheat- and barley-based diets[J]. Poultry Science, 1993, 72(9): 1731-1739. DOI:10.3382/ps.0721731
[62]
崔朝霞. 小麦饲料资源的开发利用-戊聚糖酶在肉仔鸡小麦日粮中应用的研究[D]. 硕士学位论文. 郑州: 河南农业大学, 2002.
CUI Z X. Development and utilization of wheat resources-a study on the effect of pentosanase supplementation to wheat based diets for broiler chickens[D]. Master's Thesis. Zhengzhou: Henan Agricultural University, 2002. (in Chinese)
[63]
HVBENER K, VAHJEN W, SIMON O. Bacterial responses to different dietary cereal types and xylanase supplementation in the intestine of broiler chicken[J]. Archiv für Tierernaehrung, 2002, 56(3): 167-187. DOI:10.1080/00039420214191
[64]
BEDFORD M R, APAJALAHTI J. Microbial interactions in the response to exogenous enzyme utilization[M]//BEDFORD M R, PATRIDGE G G. Enzimes in farm animal nutrition. Oxon: CABI Publishing, 2001: 299-314.
[65]
CHAPLA D, PANDIT P, SHAH A. Production of xylooligosaccharides from corncob xylan by fungal xylanase and their utilization by probiotics[J]. Bioresource Technology, 2012, 115: 215-221. DOI:10.1016/j.biortech.2011.10.083
[66]
LEE S A, APAJALAHTI J, VIENOLA K, et al. Age and dietary xylanase supplementation affects ileal sugar residues and short chain fatty acid concentration in the ileum and caecum of broiler chickens[J]. Animal Feed Science and Technology, 2017, 234: 29-42. DOI:10.1016/j.anifeedsci.2017.07.017
[67]
NIAN F, GUO Y M, RU Y J, et al. Effect of xylanase supplementation on the net energy for production, performance and gut microflora of broilers fed corn/soy-based diet[J]. Asian-Australasian Journal of Animal Sciences, 2011, 24(9): 1282-1287. DOI:10.5713/ajas.2011.10441
[68]
MELO-DURÁN D, PÉREZ J F, GONZÁLEZ-ORTIZ G, et al. Influence of particle size and xylanase in corn-soybean pelleted diets on performance, nutrient utilization, microbiota and short-chain fatty acid production in young broilers[J]. Animals, 2020, 10(10): 1904. DOI:10.3390/ani10101904
[69]
CHOCT M, SINLAE M, AI-JASSIM R A M, et al. Effects of xylanase supplementation on between-bird variation in energy metabolism and the number of Clostridium perfringens in broilers fed a wheat-based diet[J]. Australian Journal of Agricultural Research, 2006, 57(9): 1017-1021. DOI:10.1071/AR05340
[70]
JOZEFIAK D, RUTKOWSKI A, JENSEN B B, et al. Effects of dietary inclusion of triticale, rye and wheat and xylanase supplementation on growth performance of broiler chickens and fermentation in the gastrointestinal tract[J]. Animal Feed Science and Technology, 2007, 132(1/2): 79-93.
[71]
PAN D, YU Z T. Intestinal microbiome of poultry and its interaction with host and diet[J]. Gut Microbes, 2014, 5(1): 108-119. DOI:10.4161/gmic.26945
[72]
VENEGAS D P, DE LA FUENTE M K, LANDSKRON G, et al. Short chain fatty acids (SCFAs)-mediated gut epithelial and immune regulation and its relevance for inflammatory bowel diseases[J]. Frontiers in Immunology, 2019, 10: 277. DOI:10.3389/fimmu.2019.00277
[73]
KUBIŚ M, KOŁODZIEJSKI P, PRUSZY Ń SKA-OSZMAŁEK E, et al. Emulsifier and xylanase can modulate the gut microbiota activity of broiler chickens[J]. Animals, 2020, 12(10): 1297.
[74]
LAZARO R, GARCIA M, MEDEL P, et al. Influence of enzymes on performance and digestive parameters of broilers fed rye-based diets[J]. Poultry Science, 2003, 82(1): 132-140. DOI:10.1093/ps/82.1.132
[75]
VON ENGELHARDT W, BARTELS J, KIRSCHBERGER S, et al. Role of short-chain fatty acids in the hind gut[J]. The Veterinary Quarterly, 1998, 20(suppl.3): S52-S59.
[76]
POUTEAU E, ROCHAT F, JANN A, et al. Chicory increases acetate turnover, but not propionate and butyrate peripheral turnovers in rats[J]. British Journal of Nutrition, 2008, 99(2): 287-296. DOI:10.1017/S0007114507815790
[77]
YANG Y, IJI P A, CHOCT M. Dietary modulation of gut microflora in broiler chickens: a review of the role of six kinds of alternatives to in-feed antibiotics[J]. World's Poultry Science Journal, 2009, 65(1): 97-114. DOI:10.1017/S0043933909000087
[78]
WANG Y Y, HENG C N, ZHOU X H, et al. Supplemental Bacillus subtilis DSM 29784 and enzymes, alone or in combination, as alternatives for antibiotics to improve growth performance, digestive enzyme activity, anti-oxidative status, immune response and the intestinal barrier of broiler chickens[J]. The British Journal of Nutrition, 2021, 125(5): 494-507. DOI:10.1017/S0007114520002755
[79]
CHEN Q H, LI M W, WANG X. Enzymology properties of two different xylanases and their impacts on growth performance and intestinal microflora of weaned piglets[J]. Animal Nutrition, 2016, 2(1): 18-23. DOI:10.1016/j.aninu.2016.02.003
[80]
PETERSEN S T, WISEMAN J, BEDFORD M R. Effects of age and diet on the viscosity of intestinal contents in broiler chicks[J]. British Poultry Science, 1999, 40(3): 364-370. DOI:10.1080/00071669987467
[81]
BAUTIL A, VERSPREET J, BUYSE J, et al. Age-related arabinoxylan hydrolysis and fermentation in the gastrointestinal tract of broilers fed wheat-based diets[J]. Poultry Science, 2019, 98(10): 4606-4621. DOI:10.3382/ps/pez159
[82]
GAO F, JIANG Y, ZHOU G H, et al. The effects of xylanase supplementation on performance, characteristics of the gastrointestinal tract, blood parameters and gut microflora in broilers fed on wheat-based diets[J]. Animal Feed Science and Technology, 2008, 142(1/2): 173-184.
[83]
MENDES A R, RIBEIRO T, CORREIA B A, et al. Low doses of exogenous xylanase improve the nutritive value of triticale-based diets for broilers[J]. Journal of Applied Poultry Research, 2013, 22(1): 92-99. DOI:10.3382/japr.2012-00610
[84]
FIGUEIREDO A A, CORREIA B A, RIBEIRO T, et al. The effects of restricting enzyme supplementation in wheat-based diets to broilers[J]. Animal Feed Science and Technology, 2012, 172(3/4): 194-200.
[85]
DUSEL G, KLUGE H, JEROCH H, et al. Xylanase supplementation of wheat-based rations for broilers: influence of wheat characteristics[J]. Journal of Applied Poultry Research, 1998, 7(2): 119-131. DOI:10.1093/japr/7.2.119
[86]
BEDFORD M R. The evolution and application of enzymes in the animal feed industry: the role of data interpretation[J]. British Poultry Science, 2018, 59(5): 486-493. DOI:10.1080/00071668.2018.1484074
[87]
BAUTIL A, VERSPREET J, BUYSE J, et al. Arabinoxylan-oligosaccharides kick-start arabinoxylan digestion in the aging broiler[J]. Poultry Science, 2020, 99(5): 2555-2565. DOI:10.1016/j.psj.2019.12.041