日粮中木聚糖、低聚木糖和木聚糖酶对单胃动物肠道健康和生长性能的影响

存在于动物饲料中的木聚糖,已被证明会导致食糜黏度增加,从而降低营养物质的消化率和动物的生长性能。低聚木糖是由木糖单元组成的糖低聚物,可以从生物材料中提取和纯化,用作单胃动物饲料的益生元。低聚木糖也可以在动物肠道或体外通过水解木聚糖获得。日粮中添加木聚糖酶和低聚木糖对单胃动物肠道健康和生产性能的影响,以及两者的关系仍存在争论。常见谷物中会存在木聚糖酶抑制剂,且变化很大,这是另一个需要克服的障碍。随着对细菌耐药性担忧的加剧,在不使用抗生素的情况下改善动物的生长性能和肠道健康的新方法也越来越多。本综述总结了饲料中木聚糖的结构差异及其影响,各种木聚糖酶的分类和使用,以及低聚木糖的生产和使用对单胃动物肠道健康和生长性能的生理影响。本综述讨论了木聚糖的结构差异和作用、低聚木糖的生产流程及其在动物饲料中的应用。木聚糖是一种非淀粉多糖,具有β-1,4-糖苷键连接的吡喃木糖主链。由于木聚糖家族的聚合物上可取代的残基很多,某些类型的木聚糖是饲料中主要的抗营养因子。低聚木糖是从含木聚糖的木质纤维素(如农作物秸秆、木材和草本生物质)中提取的糖低聚物,具有益生元作用。当饲料中添加木聚糖酶等外源性酶时,单胃动物的肠道可以在一定程度上产生低聚木糖。添加木聚糖酶可以降低肠道食糜黏度,提高营养物质的消化利用率。由于多种因素的影响,添加木聚糖酶的效果差异很大,其中一个因素是常见饲料中存在木聚糖酶抑制剂。益生元在动物饲养中越来越受欢迎,因为生产者希望加快动物生长速度,增强肠道健康并改善其他生产参数,从而生产安全、可持续的食品。本综述还总结了木聚糖、低聚木糖以及木聚糖酶对猪和家禽生长和健康影响的研究现状。在猪和家禽饲料中添加木聚糖酶的效果变化很大,其益处究竟是来自营养物质的释放、食糜黏度的降低、短链低聚木糖的产生,还是这些益处的综合结果,目前仍存在疑问。在不同生产阶段以及不同的低聚木糖纯度和聚合度下,添加低聚木糖似乎对猪和家禽都有益处;然而,还需要进一步的研究来阐明合适的剂量、纯度和聚合度,从而对每个物种的肠道健康和生产性能产生益处。

Dietary supplementation of xylanase and protease on growth performance,digesta viscosity,nutrient digestibility,immune and oxidative stress status,and gut health of newly weaned pigs

This study was to investigate the effect of dietary supplementation with xylanase and protease on growth performance,digesta viscosity,apparent ileal digestibility(AID) of nutrients,and gut health in nursery pigs.Forty-eight pigs(24 barrows and 24 gilts at 21 d of age with 7.2±0.4 kg BW) were randomly allotted to 4 dietary treatments(2 x 2 factorial arrangement) in a randomized complete block design and fed in 2 phases(phase 1 for 10 d and phase 2 for 14 d).Factors were xylanase(0 or45,000 XU/kg) and protease(0 or 300,000 U/kg).Feed intake and BW gain were measured on d 10 and24.Titanium dioxide(0.25%) was added to all diets as an indigestible external marker from d 20 to 24.On d 24,all pigs were euthanized to obtain jejunal and ileal digesta to measure viscosity and apparent ileal digestibility.The jejunal mucosa was collected to measure immune and oxidative stress status.Jejunal tissues were used to measure morphology and crypt cells proliferation.In phase 2,xylanase increased(P <0.05) the average daily gain(ADG) which was further increased(P <0.05) when combined with protease.Overall,combinational use of xylanase and protease increased(P <0.05) ADG compared with the use of xylanase or protease alone,whereas protease improved(P <0.05) feed efficiency.In jejunum,xylanase reduced(P <0.05) viscosity of digesta,mucosal malondialdehyde(MDA),crypt depth and crypt cells proliferation,and protease increased(P <0.05) villus height,and decreased(P <0.05) crypt depth and crypt cells proliferation.Collectively,xylanase improved growth performance,digesta viscosity,and oxidative stress,whereas protease improved feed efficiency and gut morphology.The combinational use of xylanase and protease enhanced growth performance of newly weaned pigs.

Dietary inclusion of multispecies probiotics to reduce the severity of post-weaning diarrhea caused by Escherichia coli F18+ in pigs

This study was aimed to determine the efficacy of multispecies probiotics in reducing the severity of post-weaning diarrhea caused by enterotoxigenic Escherichia coli(ETEC)F18+on newly weaned pigs.Thirty-two pigs(16 barrows and 16 gilts,BW=6.99±0.33 kg)at 21 d of age were individually allotted in a randomized complete block design with 2×2 factorial arrangement of treatments.Pigs were selected from sows not infected previously and not vaccinated against ETEC.Pigs were fed experimental diets for 25 d based on 10 d phase 1 and 15 d phase 2.The factors were ETEC challenge(oral inoculation of saline solution or E.coli F18+at 2×109 CFU)and probiotics(none or multispecies probiotics 0.15%and 0.10%for phase 1 and 2,respectively).Body weight and feed intake were measured on d 5,9,13,19,and 25.Fecal scores were measured daily.Blood samples were taken on d 19 and 24.On d 25,all pigs were euthanized to obtain samples of digesta,intestinal tissues,and spleen.The tumor necrosis factor alpha(TNFα),malondialdehyde(MDA),peptide YY(PYY),and neuropeptide Y(NPY)were measured in serum and intestinal tissue.Data were analyzed using the MIXED procedure of SAS.The fecal score of pigs was increased(P<0.05)by ETEC challenge at the post-challenge period.The ETEC challenge decreased(P<0.05)jejunal villus height and crypt depth,tended to increase(P=0.056)jejunal TNFα,increased(P<0.05)ileal crypt depth,and decreased(P<0.05)serum NPY.The probiotics decreased(P<0.05)serum TNFα,tended to reduce(P=0.064)jejunal MDA,tended to increase(P=0.092)serum PYY,and increased(P<0.05)jejunal villus height,and especially villus height-to-crypt depth ratio in challenged pigs.Growth performance of pigs were not affected by ETEC challenge,whereas the probiotics increased(P<0.05)ADG and ADFI and tended to increase(P-0.069)G:F ratio.In conclusion,ETEC F18+challenge caused diarrhea,intestinal inflammation and morphological damages without affecting the growth performance.The multispecies probiotics enhanced growth performance by reducing intestinal inflammation,oxidative stress,morphological damages.