Changes in rumen fermentation and bacterial community in lactating dairy cows with subacute rumen acidosis following rumen content transplantation

摘要

Rumen microbiota intervention has long been used tocure ruminal indigestion in production and has recentlybecome a research hotspot. However, how it controlsthe remodeling of rumen bacterial homeostasis and therestoration of rumen fermentation in cows of subacuteruminal acidosis (SARA) remains poorly understood.This study explored changes in rumen fermentation andbacterial communities in SARA cows following rumencontent transplantation (RCT). The entire experimentcomprised 2 periods: the SARA induction period andthe RCT period. During the SARA induction period,12 ruminally cannulated lactating Holstein cows wereselected and allocated into 2 groups at random, fed eithera conventional diet [CON; n = 4; 40% concentrate,dry matter (DM) basis] or a high-grain diet (HG; n =8; 60% concentrate, DM basis). After the SARA inductionperiod, the RCT period began. The HG cows wererandomly divided into 2 groups: the donor-recipient(DR) group and the self-recipient (SR) group, and theirrumen contents were removed completely before RCT.For the DR group, cows received 70% rumen contentfrom the CON cows, paired based on comparable bodyweight; for the SR group, each cow received 70% rumencontent, self-derived. The results showed that nearly allrumen fermentation parameters returned to the normallevels that the cows had before SARA induction after 6d of transplantation, regardless of RCT. The concentrationsof acetate, valerate, and total volatile fatty acids(VFA) were not recovered in the SR cows, whereas allof them were recovered in the DR cows. The ampliconsequencing results indicated that both the SR and DRcows rebuild their rumen bacterial homeostasis quicklywithin 4 d after RCT, and the DR group showed ahigher level of bacterial community diversity. At thegenus level, the DR cows displayed an improved proportionof unclassified Ruminococcaceae and Saccharofermentanscompared with the SR cows. Correlationanalysis between the rumen bacteria and rumen fermentationsuggested some potential relationships betweenthe predominant transplantation-sensitive operationaltaxonomic units and VFA. Co-occurrence networkanalysis revealed that RCT affected only those rumenbacterial taxa that showed weak interactions with othertaxa and did not affect the pivotal rumen bacteria withhigh levels of co-occurrence. Our findings indicate thatRCT contributes to the restoration of rumen bacterialhomeostasis and rumen fermentation in cows sufferingfrom SARA without affecting the core microbiome.