The effect of rumen fungal flora in the susceptibility of subacute ruminal acidosis in dairy goats

Subacute rumen acidosis (SARA) is a condition commonly observed in high-yielding dairy cows, typically resulting from prolonged feeding of high-concentration diets (HCD). However, differences exist in whether SARA develops in the rumen when cows are fed diets with identical or similar nutrient compositions. The rumen fungal microbiota may play a crucial role in the digestion of plant fibers and carbohydrates in ruminants. In this study, we analyzed the rumen fungal microbiota of SARA-tolerant (ST) and SARA susceptible (SS) dairy goats before and after they were fed a HCD. ITS rRNA sequencing revealed that the relative abundance of Fusarium , Exophiala , Trichoderma , Cephalotrichum , Paraxerochrysium , Robillarda and Kondoa was higher in the ST group, whereas the relative abundance of Phallus , Glaciozyma , and Paraxerochrysium y was reduced in ST group goats compared to the SS group. In addition, compared to the SS-B group, the dominant Ascomycota in the ST-B group produced cellulase, which is beneficial for stabilizing rumen pH. What’s more, the SS-B group had a more dominant Basidiomycetes producing lignin degrading enzymes, promoting the production of SCFA and leading to a decrease in rumen pH. In addition, the dominant fungal strains in the ST-B group also include Konda , the most common probiotic fungal yeast in the rumen. In conclusion, this study suggests that the composition of the rumen fungal microbiota may be associated with SARA susceptibility, and modulating the fungal microbiota can provide a novel approach to prevent SARA in ruminants.