Queensland Alliance for Agriculture and Food Innovation, Centre for Animal Science, The University of Queensland, St Lucia, QLD, Australia.
School of Agriculture and Food Sciences, The University of Queensland, Gatton, QLD, Australia.
J Anim Sci. 2021 Feb 1;99(2). doi: 10.1093/jas/skab017.
The objective was to evaluate the effects of a specific strain of live yeast (LY) on growth performance, fermentation parameters, feed efficiency, and bacterial communities in the rumen of growing cattle fed low-quality hay. In experiment (exp.) 1, 12 Droughtmaster bull calves (270 ± 7.6 kg initial body weight [BW]) were blocked by BW into two groups, allocated individually in pens, and fed ad libitum Rhodes grass hay (8.4% of crude protein [CP]) and 300 g/bull of supplement (52% CP) without (Control) or with LY (8 × 109 colony-forming unit [CFU]/d Saccharomyces cerevisiae CNCM I-1077; Lallemand Inc., Montreal, Canada) for 28 d, followed by 7 d in metabolism crates. Blood and rumen fluid were collected before feeding and 4 h after feeding. In exp. 2, for assessment of growth performance, 48 Charbray steers (329 ± 20.2 kg initial BW) were separated into two blocks by initial BW and randomly allocated into 12 pens. The steers were fed Rhodes grass hay (7.3% CP) and 220 g/steer of supplement (60% CP) without or with LY (8 × 109 CFU/d) for 42 d, after a 2-wk adaptation period. In exp. 1, fiber digestibility was calculated from total fecal collection, and, in exp 2, indigestible neutral detergent fiber (NDF) was used as a marker. Inclusion of LY increased (P = 0.03) NDF intake by 8.3% in exp. 1, without affecting total tract digestibility. No changes were observed in microbial yield or in the efficiency of microbial production. There was a Treatment × Time interaction (P < 0.01) for the molar proportion of short-chain fatty acids, with LY increasing propionate before feeding. Inclusion of LY decreased rumen ammonia 4 h after feeding (P = 0.03). The addition of LY reduced rumen bacterial diversity and the intraday variation in bacterial populations. Relative populations of Firmicutes and Verrucomicrobia varied over time (P < 0.05) only within the Control group. At the genus level, the relative abundance of an unclassified bacterial genus within the order Clostridiales, a group of cellulolytic bacteria, was reduced from 0 to 4 h after feeding in the Control group (P = 0.02) but not in the LY group (P = 1.00). During exp. 2, LY tended to increase average daily gain (ADG) (P = 0.08) and feed efficiency (P = 0.10), with no effect on NDF intake or digestibility. In conclusion, S. cerevisiae CNCM I-1077 reduced the intraday variation of rumen bacteria and increased the amount of NDF digested per day. These observations could be associated with the tendency of increased ADG and feed efficiency in growing cattle fed a low-quality forage.
目的是评估特定活酵母（LY）菌株对生长性能、发酵参数、饲料效率和低质量干草喂养生长牛瘤胃细菌群落的影响。在实验（exp.）1 中，12 头抗旱种公牛犊（初始体重 [BW]270±7.6kg）按 BW 分为两组，个体分配到围栏中，自由采食罗兹草干草（粗蛋白 [CP]8.4%）和 300g/头补充料（CP52%），不添加（对照）或添加 LY（8×109 个 CFU/d 酿酒酵母 CNCM I-1077；Lallemand Inc.，蒙特利尔，加拿大）28d，然后在代谢箱中 7d。在喂食前和喂食后 4h 采集血液和瘤胃液。在 exp.2 中，为评估生长性能，将 48 头 Charbray 阉牛（初始 BW329±20.2kg）按初始 BW 分为两部分，并随机分配到 12 个围栏中。牛只自由采食罗兹草干草（CP7.3%）和 220g/头补充料（CP60%），不添加或添加 LY（8×109CFU/d）42d，适应期 2 周。在 exp.1 中，通过总粪便收集计算纤维消化率，在 exp.2 中，使用不可消化中性洗涤剂纤维（NDF）作为标记。添加 LY 使 exp.1 中的 NDF 摄入量增加了 8.3%，但不影响全肠道消化率。微生物产量或微生物生产效率没有变化。短链脂肪酸摩尔比例存在处理×时间交互作用（P<0.01），添加 LY 可增加丙酸前的丙酸产量。添加 LY 可减少 4h 后瘤胃中的氨（P=0.03）。添加 LY 降低了瘤胃细菌多样性和细菌种群的日内变化。厚壁菌门和疣微菌门的相对种群随时间变化（P<0.05），仅在对照组中发生变化。在属水平上，对照组成员中一个未分类的拟杆菌门属的相对丰度在 0 到 4h 之间降低（P=0.02），但在 LY 组中没有降低（P=1.00）。在 exp.2 中，LY 趋于增加平均日增重（ADG）（P=0.08）和饲料效率（P=0.10），而对 NDF 摄入量或消化率没有影响。总之，酿酒酵母 CNCM I-1077 降低了瘤胃细菌的日内变化，并增加了每天消化的 NDF 量。这些观察结果可能与低质量饲草喂养的生长牛 ADG 和饲料效率增加的趋势有关。
