Mohammed R, Vyas D, Yang W Z, Beauchemin K A
Lethbridge Research and Development Center, Agriculture and Agri-Food Canada, Lethbridge, AB, Canada.
J Appl Microbiol. 2017 Jun;122(6):1483-1496. doi: 10.1111/jam.13451. Epub 2017 May 11.
To characterize the changes in the relative population size (RPS) of select ruminal bacteria and rumen fermentation variables in beef heifers supplemented with a strain of Saccharomyces cerevisiae as viable active dried (ADY) or killed dried (KDY) yeast following an induced episode of ruminal acidosis.
Six ruminally cannulated beef heifers fed a diet consisting of 50% forage and 50% grain (dry matter basis) were used in a replicated 3 × 3 Latin square design with three 28-day periods. Treatments were: (i) control (CTRL; no yeast); (ii) ADY (4 g day providing 10 CFU per g; AB Vista, UK); and (iii) KDY (4 g day autoclaved ADY). The acidosis challenge was induced on day 22 and rumen samples were collected on day 15 (baseline; BASE), day 22 (challenge day; CHAL), and on day 29 (168th hour post acid challenge or recovery, REC) of each period. Over the study, duration of pH <5·8 (indicative of subacute ruminal acidosis) was less for ADY and KDY than CTRL, with ADY less than KDY. No treatment effects were observed on relative abundance of ruminal bacteria, but the day effect was significant. The RPS of lactate producers and utilizers was greater while RPS of fibrolytic bacteria was lower during CHAL than BASE and REC. Yeast supplementation, irrespective of its viability, showed beneficial effects on ruminal pH variables in animals more susceptible to acidosis.
Rumen microbial population was altered with the induction of severe acidosis. Most of the changes reverted back to baseline values during the recovery phase. Yeast supplementation reduced subacute rumen acidosis in the most susceptible cattle, but failed to attenuate severe acidosis induced by a grain challenge.
The study provided valuable insight into the mechanism by which acidosis affects cattle performance. Individual animal variation in ruminal fermentation partly explained the variability in response to yeast supplementation in the study.
表征在瘤胃酸中毒诱发期后，给育肥肉牛补充酿酒酵母活的活性干酵母（ADY）或灭活干酵母（KDY）时，特定瘤胃细菌的相对种群大小（RPS）和瘤胃发酵变量的变化。
选用6头安装了瘤胃瘘管的育肥肉牛，饲喂由50%粗饲料和50%谷物组成的日粮（干物质基础），采用重复的3×3拉丁方设计，共3个28天周期。处理方式为：（i）对照（CTRL；不添加酵母）；（ii）ADY（每天4 g，每克含10⁸CFU；英国AB Vista公司）；（iii）KDY（每天4 g，经高压灭菌处理后的ADY）。在每个周期的第22天诱发酸中毒挑战，并在第15天（基线期；BASE）、第22天（挑战日；CHAL）和第29天（酸挑战后或恢复的第168小时；REC）采集瘤胃样本。在整个研究过程中，ADY组和KDY组pH<5.8（表明亚急性瘤胃酸中毒）的持续时间比CTRL组短，且ADY组短于KDY组。在瘤胃细菌的相对丰度上未观察到处理效应，但日效应显著。与BASE期和REC期相比，CHAL期乳酸产生菌和利用菌的RPS更高，而纤维分解菌的RPS更低。无论酵母的活力如何，补充酵母对更易发生酸中毒的动物的瘤胃pH变量均显示出有益作用。
严重酸中毒的诱发改变了瘤胃微生物种群。在恢复阶段，大多数变化恢复到基线值。补充酵母可减轻最易感牛的亚急性瘤胃酸中毒，但未能减轻谷物挑战诱发的严重酸中毒。
该研究为酸中毒影响牛生产性能的机制提供了有价值的见解。瘤胃发酵的个体动物差异部分解释了本研究中补充酵母反应的变异性。
