Effect of oligosaccharide addition on rumen bacterial flora of lactating calves

The effects of different methods mannose oligosaccharide (MOS) addition on the construction of rumen bacteria in calves were studied based on 16S rDNA sequencing. Twenty healthy male Holstein calves with similar weights and of the same age were selected and randomly divided into four groups. The control group (CR) was fed a basal diet of milk with no MOS added. In the ORa group, 5 g MOS was added to the milk rather than the diet. In the ORb group, 5 g MOS was added to the diet rather than the milk. In ORc group, 2.5 g MOS was added to both the milk and diet, respectively. The results showed that the different methods of MOS addition affected the total amount of rumen bacteria, but no significant influence on the diversity of rumen bacteria in calves was found. At the phylum level, compared with that of the control group, the addition of MOS in the ORb group significantly reduced the abundance of Firmicutes and Actinomycetes (P < 0.05) and significantly increased the abundance of Proteobacteria ( P < 0.01). The dominant bacteria in the ORb group increased to 3 species (Bacteroidetes, Firmicutes, and Proteobacteria). At the genus level, the different methods of MOS addition effected the structure of rumen bacteria of the calves to some extent, including Dialister and Desulfovibrio. While the variables had fewer effects on the rumen bacteria of calves in the ORa and ORc groups compared to that of the ORb group. Moreover, the functional rumen bacteria of the calves in the ORb group were all significantly affected, including prevoort-7, amino acid cocci, eubacterium, and vibrio succinate. In this experiment, the different ways of adding MOS had no significant impact on the diversity of rumen bacteria of suckling calves. However, the method of MOS addition in the starter had some effects on the structure of the flora, among which the abundance of Succinivibrionaceae_UCG-001, which played a role in both rumen protein degradation and starch degradation, significantly increased. The abundance of Selenomonas using lactic acid significantly increased, and the abundance of Eubacterium_coprostanoligenes_group using lactose significantly reduced, while the abundance of Dialister degrading hemicellulose significantly reduced.