Associations Between RFI, and Metabolite Profiles and Feeding Behavior Traits in Feedlot Cattle
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Objectives of this study were characterize residual feed intake (RFI) in finishing steers to examine relationships with performance, feed efficiency, feeding behavior traits, and blood metabolite profiles and identify biomarkers (feeding behavior traits and blood metabolites) to understand underlying biological mechanisms of RFI. Performance, DMI, and feeding behavior traits were measured for 70 d in Angus crossbred steers (N = 168) using a GrowSafe system. Steers were classified into low (n = 52), medium (n = 64), and high (n = 52) RFI groups based on ± 0.5 SD from the mean RFI of 0.00 (SD = 0.82). Partial least squares (PLS; MetaboAnalyst) were used to examine associations between RFI, and feeding behavior traits and metabolites. Components 1 and 2 of the PLS analysis accounted for 39.1% of between animal variance in RFI, and 4 feeding behavior traits had a variable of importance in projection (VIP) score > 1, which included HD duration, BV duration, HD to meal duration ratio, and bite frequency. Steers with low RFI had 15% greater (P < 0.0001) bite frequency, 34% lower HD duration, 24% lower BV duration, and 24% lower HD : MD ratio than high RFI steers. To examine associations between RFI and blood metabolite profiles to identify RFI biomarkers, blood was collected on day 0 and 70 of the trial for steers with RFI that were ± 1 SD from the mean RFI (0.00 ± 0.82 kg/d), which included 25 low and 24 high-RFI steers. Partial least squares analysis of day 0 metabolite profiles resulted in overfitting of the data (P = 0.264), but day 70 metabolite data was not over-fitted (P = 0.009). Components 1 and 2 of the PLS analysis accounted for 34.2% of between animal variance in RFI. Of the 44 metabolites detected by 1H-NMR, 5 metabolites had VIP scores > 2, which included glycine, betaine, tyrosine, valine, and leucine. Steers with low-RFI had 54% higher (P < 0.0003) concentrations of glycine, and 14% lower (P < 0.05) concentrations of betaine, 12% lower (P < 0.05) concentration of tyrosine, 9% lower (P < 0.06) concentration of valine, and 14% lower (P < 0.04) concentration of leucine than high-RFI steers. Results from this study indicate glycine, betaine, tyrosine, valine, and leucine are possible biomarkers for identification of feed-efficient cattle. Further studies are needed to evaluate the repeatability and robustness across breeds, diets, etc. for these metabolites.
Miller, Michael Devin (2016). Associations Between RFI, and Metabolite Profiles and Feeding Behavior Traits in Feedlot Cattle. Master's thesis, Texas A & M University. Available electronically from