Predictive ability of host genetics and rumen microbiome for subclinical ketosis

摘要

Subclinical metabolic disorders such as ketosis causesubstantial economic losses for dairy farmers in additionto the serious welfare issues they pose for dairycows. Major hurdles in genetic improvement againstmetabolic disorders such as ketosis include difficultiesin large-scale phenotype recording and low heritabilityof traits. Milk concentrations of ketone bodies, such asacetone and β-hydroxybutyric acid (BHB), might beuseful indicators to select cows for low susceptibilityto ketosis. However, heritability estimates reported formilk BHB and acetone in several dairy cattle breedswere low. The rumen microbial community has beenreported to play a significant role in host energy homeostasisand metabolic and physiologic adaptations.The current study aims at investigating the effects ofcows’ genome and rumen microbial composition onconcentrations of acetone and BHB in milk, and identifyingspecific rumen microbial taxa associated withvariation in milk acetone and BHB concentrations. Wedetermined the concentrations of acetone and BHB inmilk using nuclear magnetic resonance spectroscopy onmorning milk samples collected from 277 Danish Holsteincows. Imputed high-density genotype data wereavailable for these cows. Using genomic and microbialprediction models with a 10-fold resampling strategy,we found that rumen microbial composition explainsa larger proportion of the variation in milk concentrationsof acetone and BHB than do host genetics. Moreover,we identified associations between milk acetoneand BHB with some specific bacterial and archaeal operationaltaxonomic units previously reported to havelow to moderate heritability, presenting an opportunityfor genetic improvement. However, higher covariationbetween specific microbial taxa and milk acetone andBHB concentrations might not necessarily indicatea causal relationship; therefore further validation isneeded before considering implementation in selectionprograms.