The effect of different forages on rumen microbiota and milk production performance in Holstein dairy cows

Optimising the feed composition, especially the forage choice, and reducing costs are essential for improving dairy production efficiency. Different forage sources and proportions were used toformulate rations containing equal energy and protein, and their effects onrumen microbiota and milk production performance ofdairy cows were evaluated intwo experiments. Inexperiment 1, thirty lactating cows (235±13 d postpartum; milk production 29.1±1.0kg/day)were divided into Pangola and Bermuda groups. Inexperiment 2, twenty lactating cows (79.9±8.1d postpartum; milk production 34.7 ± 0.6kg/day) were divided into Pangola and oat groups. Inexperiment 1, the Simpson index for rumen microbiota ofthe Pangola group was significantly higher than inthe Bermuda group (P<0.05). Analysis ofthe weighted unique fraction (UniFrac) distances indicated significant differences inthe beta diversity ofthe community composition ofrumen microbiota between Pangola, Bermuda and oat groups inboth experiments (P< 0.001). The relative abundance ofPrevotella brevis was significantly higher inthe Pangola group than inthe oat group inexperiment 2 (P< 0.05). The somatic cell counts (SCCs), C18:0, and C18:1 inmilk were significantly higher inthe Bermuda group than inthe Pangola group (P< 0.05) inexperiment 1. Onthe other hand, milk crude protein (CP) and solids-not-fat (SNF) were significantly higher inthe Oat group than inthe Pangola group (P<0.05) inexperiment 2; however, milk urea nitrogen (MUN) was significantly higher inthe Pangola group (P<0.05). Inconclusion, aswitch offorage (Pangola vs Bermuda) at a lower proportion ofthe diet under the high forage level condition (experiment 1) caused only minor changes inrumen microbiota diversity (Simpson index, beta diversity) and milk production performance (milk SCCs, C18:0 and C18:1). Onthe other hand, aswitch offorage (Pangolavs oat) at a higher proportion ofthe diet under the low forage level condition (experiment 2) resulted ingreater changes inrumen microbiota diversity (beta diversity, relative abundances ofbacterial taxa, P. brevis relative abundance) and milk production performance (milk CP, SNF, and MUN).