Rumen Microbial Species Associated With Feed Efficiency in Sheep Fed a Forage-Based Diet
The rumen microbial ecosystem plays a dominant role in fermentation of consumed feeds in ruminant livestock, and therefore influences the efficiency of feed utilization. Determination of rumen microbial species important to feed efficiency may ultimately lead to development of technologies to aid producers in selecting more efficient seedstock. Our objective was to identify rumen microbial species associated with variation in feed efficiency in lambs fed a forage-based diet. Briefly, growing wethers (initial BW = 51.5 ± 1.7 kg; n = 38) of Rambouillet, Suffolk, and Hampshire breed backgrounds were administered a forage-based pelleted diet and individual feed intake was collected using a GrowSafe system over a 7 wk period. Residual feed intake (RFI) was estimated for each lamb, and subsequently used to rank lambs for feed efficiency. The most efficient (low-RFI; n = 4) and the least efficient (high-RFI; n = 4) lambs were selected for sequencing of DNA isolated from respective rumen fluid samples. Pair-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. Abundance of 28 OTUs differed (P < 0.05) with feed efficiency status, with the majority (n = 18) of these being Prevotella species. Of particular interest were Ruminococcus flavefaciens and Ruminococcus albus, two predominant rumen fibrolytic bacterial species involved in cellulose digestion. Unexpectedly, these two bacteria were in greater (P < 0.001) abundance in high-RFI lambs (3.2 fold greater for R. flavefaciens; 1.5 fold greater for R. albus). This may be due to differences in diet quality and form (i.e. pelleted), as previous studies have indicated that changes in abundance of such fibrolytic species can be associated with diet differences. Data from this study suggest that rumen microbial populations differ with feed efficiency status; however, certain species may be prone to variations in diet quality and presentation.
feed efficiency, microbes, rumen, sheep