The Effect of Residual Feed Intake on Rumen Microbial Profiles in Growing Ewe Lambs

The rumen microbiome is known to play a paramount role in fermentation of consumed feedstuffs in ruminant livestock, and therefore may influence the efficiency of feed utilization. The objective of this study was to determine the effect of feed efficiency status on rumen microbial profiles in growing ewe lambs. Growing Targhee ewe lambs (initial BW = 55.7 ± 1.2 kg; n = 78) were fed a forage-based pelleted diet. Individual feed intake was measured with a GrowSafe System for 70 d and initial, mid, and final BW were recorded to allow for estimation of feed efficiency. Rumen fluid samples were collected at the end of the feeding trial, and DNA was extracted for sequencing from the rumen fluid of the eight most (low RFI) and eight least efficient (high RFI) ewes. Paired-end reads were filtered, quality trimmed and compared with a database of known 16S rDNA genes. Operational taxonomic units (OTU) were defined as sequence clusters with ≥ 97% identity. There were 306 OTUs present in at least one animal. Of the 6 OTUs observed to differ with RFI status, 4 were of greater (P ≤ 0.044) abundance in high RFI ewes, including Prevotella bryantii, Ruminococcus albus, Schwartzia succinivorans and Mannheimia haemolytica. Methanobrevibacter smithii and an unknown Prevotella species were of greater (P ≤ 0.044) abundance in low RFI ewes. These data suggest that certain species in the rumen microbiome may contribute to variation in host feed efficiency.