Department of Animal Science, Hokkaido University, Sapporo, Japan 060-8589.
Department of Animal Science, Hokkaido University, Sapporo, Japan 060-8589.
J Dairy Sci. 2021 Oct;104(10):10744-10752. doi: 10.3168/jds.2021-20225. Epub 2021 Jul 1.
In our previous studies, we revealed the effect of lactose inclusion in calf starters on the growth performance and gut development of calves. We conducted the present study as a follow-up study to identify the shift in rumen microbiota and its relation to rumen fermentation when calves are fed a lactose-containing starter. Thirty Holstein bull calves were divided into 2 calf starter treatment groups: texturized calf starter (i.e., control; n = 15) or calf starter in which starch was replaced with lactose at 10% (i.e., LAC10; n = 15) on a dry matter basis. All calves were fed their respective treatment calf starter ad libitum from d 7, and kleingrass hay from d 35. Rumen digesta were collected on d 80 (i.e., 3 wk after weaning) and used to analyze rumen microbiota and fermentation products. There was no apparent effect of lactose feeding on the α-diversity and overall composition of rumen microbiota. Amplicon sequencing and real-time PCR quantification of the 16S rRNA gene confirmed that the abundance of butyrate-producing bacteria (i.e., Butyrivibrio group and Megasphaera elsdenii) did not differ between the control and LAC10 groups. Conversely, the relative abundance of Mitsuokella spp., which produce lactate, succinate, and acetate, was significantly higher in the rumen of calves that were fed lactose, whereas the lactate concentration did not differ between the control and LAC10 groups. These findings suggest that the lactate production can be elevated by an increase of Mitsuokella spp. and then converted into butyrate, not propionate, since the proportion of propionate was lower in lactose-fed calves. In addition, we observed a higher abundance of Coriobacteriaceae and Pseudoramibacter-Eubacterium in the LAC10 group. Both these bacterial taxa include acetate-producing bacteria, and a positive correlation between the acetate-to-propionate ratio and the abundance of Pseudoramibacter-Eubacterium was observed. Therefore, the higher abundance of Coriobacteriaceae, Mitsuokella spp., and Pseudoramibacter-Eubacterium in the rumen of lactose-fed calves partially explains the increase in the proportion of rumen acetate that was observed in our previous study.
在我们之前的研究中，揭示了在犊牛代乳料中添加乳糖对犊牛生长性能和肠道发育的影响。本研究作为后续研究，旨在确定当犊牛饲喂含有乳糖的代乳料时，瘤胃微生物群的变化及其与瘤胃发酵的关系。30 头荷斯坦公牛犊随机分为 2 个犊牛代乳料处理组：膨化犊牛代乳料（即对照组；n = 15）或用乳糖替代 10%淀粉的犊牛代乳料（即 LAC10；n = 15），基于干物质。所有犊牛从第 7 天开始自由采食各自的代乳料，从第 35 天开始采食kleingrass 干草。在断奶后第 80 天（即断奶后 3 周）收集瘤胃液，用于分析瘤胃微生物群和发酵产物。乳糖饲喂对瘤胃微生物群的 α-多样性和总体组成没有明显影响。16S rRNA 基因的扩增子测序和实时 PCR 定量证实，丁酸产生菌（即丁酸弧菌属和 Megasphaera elsdenii）的丰度在对照组和 LAC10 组之间没有差异。相反，在饲喂乳糖的犊牛瘤胃中，产乳酸、琥珀酸和乙酸的 Mitsuokella 属的相对丰度显著升高，而对照组和 LAC10 组之间的乳酸浓度没有差异。这些发现表明，Mitsuokella 属的增加可以提高乳酸的产生，然后转化为丁酸，而不是丙酸，因为饲喂乳糖的犊牛的丙酸比例较低。此外，我们观察到 LAC10 组中 Coriobacteriaceae 和 Pseudoramibacter-Eubacterium 的丰度更高。这两个细菌类群都包括产乙酸菌，并且观察到乙酸与丙酸的比例与 Pseudoramibacter-Eubacterium 的丰度呈正相关。因此，在饲喂乳糖的犊牛瘤胃中，Coriobacteriaceae、Mitsuokella 属和 Pseudoramibacter-Eubacterium 的丰度增加，部分解释了我们之前研究中观察到的瘤胃乙酸比例增加的原因。
