Identification of lactic acid bacteria in the feces of dairy cows fed whole crop maize silage to assess the survival of silage bacteria in the gut

In order to assess the survival of lactic acid bacteria (LAB) in whole crop maize silage in the gut of dairy cows, one representative silage sample and three different feces samples were collected from dairy cows on three dairy farms in Hua Bei, China and three dairy farms in Kyushu, Japan. The composition of the bacterial community was examined by denaturing gradient gel electrophoresis and quantitative polymerase chain reaction. Lactobacillus acetotolerans was detected in all bunker‐made maize silage samples, regardless of the dairy farm or sampling region from which they were sourced. A total of eight LAB species were detected in the maize silage samples, of which three (L. acetotolerans, L. pontis and L. casei) appeared to survive digestion. The populations of L. acetotolerans in silage and feces were 10^6–7 and 10^3–4 copies/g, respectively, indicating that, even for the LAB species showing potential survival in the gut, competition in this niche may be harsh and the population may substantially decrease during the digestion process. It may be difficult for silage LAB to survive in the gut of silage‐fed dairy cows, because marked decrease in population can take place during the digestion process, even for surviving species.     

Influences of quorum‐quenching probiotic bacteria on the gut microbial community and immune function in weaning pigs

The aim of this study is to investigate the dynamic gut microbial diversity in weaning swine after administering feed supplemented with probiotic bacteria that specifically inhibit the activity of quorum molecules. Initially, the universal quorum molecule autoinducer‐2 (AI‐2) bioassay results indicated that AI‐2 activity was profoundly inhibited in enterohemorrhagic Escherichia coli (EHEC) O157:H7 in the presence of Lactobacillus acidophilus strain 30SC cell extract, although the growth of EHEC was not affected. Based on plate counting results, bacterial community analysis revealed a specific reduction in coliforms compared to the control, whereas the population of lactobacilli increased in weaning swine in in vivo trials. Supplementation with L. acidophilus strain 30SC did not affect the counts of other communities, such as total aerobes and yeast/mold. In addition, PCR‐denaturing gradient gel electrophoresis analysis showed a significant difference in the 16S rRNA gene products after administering L. acidophilus strain 30SC. Selected bands were sequenced, and most of them were identified as uncultured bacterium clones or a Lactobacillus‐ and Bifidobacterium‐specific community. Therefore, our results indicate that quorum‐quenching probiotic bacteria can significantly modulate the gut microbiota of swine and these beneficial effects can contribute to the improvement of performance and health in the gastrointestinal tract of weaning pigs.     

包衣技术提高药物药学性能的研究进展

兽药对畜牧生产中的疾病防控和健康养殖意义重大,但由于某些药物味苦、对胃黏膜刺激性大、稳定性差和药理作用部位靶向性差等限制了其在临床上的使用。包衣技术在改善药物适口性、提高药物稳定性和实现药物控缓释和靶向性等方面具有显著优势。作者总结了国内外关于包衣技术在改善药物适口性、提高药物稳定性、制备控缓释剂型和高效靶向释药剂型方面的研究进展,分析了包衣膜的形成原理,剖析了几种常见包衣技术的优缺点和其产业化面临的挑战,在此基础上展望了包衣技术在兽药领域的应用前景,以期为基于包衣技术的兽药新制剂的开发提供新思路。     

贵州省猪源大肠杆菌对四环素类药物的耐药性及耐药基因检测

为考察贵州省猪源大肠杆菌对四环素类抗菌药的耐药情况和耐药基因的流行情况,本试验采用微量肉汤稀释法测定783株分离于贵州省8个地区规模化养殖场的猪源大肠杆菌对6种四环素类药物的敏感性,并通过PCR方法检测其携带四环素耐药基因情况。结果显示,猪源大肠杆菌对土霉素、四环素、金霉素、多西环素、米诺环素和替加环素的耐药率分别为97.3%、97.6%、96.6%、89.3%、48.0%和34.2%;土霉素和四环素的耐药水平最高,其MIC₅₀分别为256 和128 μg/mL,而MIC₉₀均为512 μg/mL,四环素的耐药倍数高于土霉素;米诺环素和替加环素的耐药水平最低,其MIC₉₀分别为32和4 μg/mL,耐药倍数相同;耐药基因tetA、tetB、tetC、tetD和tetM的检出率分别为92.60%、41.50%、58.75%、58.62%和70.10%;耐药菌株中主要以tetA基因为主,且大多数以携带复合基因的形式存在;大肠杆菌对土霉素、四环素、金霉素、多西环素和米诺环素的耐药性分别与耐药基因tetB和tetM呈极显著相关（P<0.01）,tetD基因分别与对米诺环素和替加环素的耐药性呈极显著相关（P<0.01）。贵州省猪源大肠杆菌对四环素类药物的耐药情况十分普遍,尤其是四环素和土霉素,金霉素和强力霉素有高度耐药的趋势;外排泵是四环素类药物主要的耐药机制;在兽医临床上越来越严重的耐药情况与耐药基因的广泛存在有很大关系。     

Identical genotypes of community‐associated MRSA (ST59) and livestock‐associated MRSA (ST9) in humans and pigs in rural China

This study investigated the prevalence of MRSA in samples taken in households, with and without backyard pigs in villages in a rural area of Shandong Province, China. Community‐associated MRSA and livestock‐associated MRSA, belonging to ST59 and ST9, respectively, were identified in both humans and pigs. The genotypic and phenotypic comparison of isolates indicates that bidirectional transmission of MRSA has occurred between humans and pigs in the villages.     

瘤胃中乳酸的代谢及其调控机制

有关瘤胃酸中毒发生机制研究表明,瘤胃乳酸的累积可能对酸中毒诱导起重要作用,而高精料日粮下瘤胃乳酸累积主要取决于瘤胃乳酸产生菌和乳酸利用菌间的平衡程度。本文综述了瘤胃微生物对乳酸的代谢机制,包括主要乳酸产生菌[溶纤维丁酸弧菌(Butyrivibrio fibrisolvens)、牛链球菌(Streptococcus bovis)、乳酸杆菌(Lactobacillus)]和主要乳酸利用菌[反刍兽新月单胞菌(Selenomonus ruminantium)、埃氏巨型球菌(Megasphaera elsdenii)],并简要概述了酸中毒的调控方法,旨在为反刍动物瘤胃酸中毒的乳酸中毒机制深入解析提供参考。     

单一和复合乳酸菌添加水平对苜蓿青贮营养品质及蛋白组分的影响

以第1茬现蕾期刈割的紫花苜蓿(Medicago sativa)为原料(干物质含量为42.56%),结合康奈尔碳水化合物-蛋白质体系(CNCPS),研究不同浓度的单一和复合乳酸菌对苜蓿青贮品质及蛋白组分的影响。发酵40d后取样分析其青贮发酵品质和营养成分,结果表明,所有乳酸菌处理组都能显著降低苜蓿青贮饲料的氨态氮含量(P0.05),并且均未检测到丁酸;添加量为1×10~7 cfu·g~(-1)的单一乳酸菌处理组氨态氮含量最低,乳酸含量最高;除添加量为1×10~5cfu·g~(-1)的复合菌处理组外,其它乳酸菌处理组的pH均显著低于无添加剂处理组(P0.05);乳酸菌处理后粗蛋白含量无显著变化(P0.05);复合菌处理组的非蛋白氮含量显著低于无添加剂处理组(P0.05);单一和复合乳酸菌都能降低蛋白组分中的非蛋白氮(PA)含量,增加快速降解真蛋白质(PB1)和中速降解真蛋白质(PB2)含量,复合菌处理的真蛋白质(PB)含量显著高于对照的(P0.05)。综上所述,高浓度的单一植物乳杆菌(Lactobacillus plantarum)处理的苜蓿青贮发酵品质最好,复合菌能保护更多的真蛋白不被降解。     

松嫩草地不同植物功能群土壤细菌的碳源利用

基于Biolog-Eco技术,研究了长期受放牧干扰的松嫩草地羊草(Leymus chinensis)、禾草、豆科植物和杂类草4类植物功能群土壤细菌碳源利用规律。结果表明,4类植物功能群土壤细菌碳源利用情况各不相同。其中,杂类草功能群土壤细菌代谢活性最高,其次是禾草功能群、羊草功能群,豆科植物功能群最低。4类植物功能群土壤细菌均对糖类和氨基酸这两类碳源利用较好,对酚酸和胺类这两类碳源利用情况较差。杂类草的Shannon-Wiener指数,Pielou均匀度指数以及Gini多样性指数最高,而豆科的最低。冗余分析(RDA)表明,土壤中全氮和有机质对杂类草及豆科植物功能群土壤细菌碳源利用情况影响较大,电导率、pH以及含水量则对羊草和禾草功能群土壤细菌碳源利用情况影响较大。     

磷化氢熏杀其抗性害虫实仓试验

用磷化铝片对储藏在房式仓（仓容５１６ｍ３）中的４００ｔ散装小麦进行熏蒸。储 不小麦水分为１１．５％,储藏平均温度为２９．３℃,小麦用ＰＶＣ（厚度０．１２５ｍｍ）复盖。熏 蒸期间用磷化氢检测管测定ＰＨ3浓度。采用１．０３ｋｇ磷化铝片（可释放０．３４ｋｇ磷化氢） 分成小包进行熏蒸,磷化氢最高值为 １． ０ｍｇ／Ｌ。熏蒸 １６天的 ＣＴ值为 ２１３ｍｇ· ｈ／Ｌ。用 敏感和抗性品系的米象和谷蠹进行生物试验表明．熏蒸１个月后所有的成虫都死亡;熏 蒸４２天所有中度抗性的谷蠹没有发现Ｆ１代成虫出现．米象的印和蛹不能发育为成虫。