September 02, 2020

Interpretive Summary: Ruminal cellulolytic bacteria alter fatty acid composition of rumen digesta in fattening lambs

Interpretive Summary: Ruminal cellulolytic bacteria alter fatty acid composition of rumen digesta in fattening lambs

By: Anne Kamiya, MS

High-yielding lactating dairy cows and fattening lambs are at-risk for subacute rumen acidosis (SARA), a serious nutrition-related metabolic disease. Ruminal pH and propionate concentration generally assess risk for SARA. Propionate is a fatty acid (FA) produced during fermentation by rumen bacteria. Low pH and high concentrations of propionate in rumen digesta are generally associated with lower SARA risk. However, despite being fed the same diet, pH and propionate concentration can still vary widely among animals.

In this recent Journal of Animal Science article, researchers hypothesized that cellulolytic bacteria would impact the FA composition of rumen digesta and muscle tissue in fattening lambs. Since these bacteria are carbohydrate fermenters and very sensitive to changes in rumen pH, the authors suggested they may also be a potential biomarker for SARA risk.

Fattening lambs were fed a high-concentrate diet. Rumen fluid, digesta and muscle tissue were evaluated for FA content and bacterial composition. Lambs were categorized as having either lower cellulolytic bacteria (LCB) or higher cellulolytic bacteria (HCB). Different FA compositions of rumen digesta and muscle tissue were identified in LCB versus HCB lambs. Rumen concentrations of valerate, polyunsaturated fatty acids (PUFA), and odd- and branched-chain fatty acids (OBCFA) were higher in HCB lambs. Increased valerate is associated with higher SARA risk, making this finding significant. The LCB lambs had lower rumen pH compared to HCB lambs, suggesting a lower risk for SARA.

Overall, this study supports the authors’ hypothesis that ruminal cellulolytic bacteria impact the FA composition of rumen digesta and muscle tissue in lambs. These bacteria may also potentially be a biomarker for SARA risk. Future studies may benefit from in-depth investigation into the relationship between SARA risk and LCB/HCB dairy cows or lambs.  

The original article, Ruminal cellulolytic bacteria abundance leads to the variation in fatty acids in the rumen digesta and meat of fattening lambs, is viewable in the Journal of Animal Science.