Associations between RFI, and metabolite profiles and feeding behavior traits in feedlot cattle

Abstract Text: Objectives of this study were to evaluate the effects of residual feed intake (RFI) classification on performance and feed efficiency in steers fed a high grain diet, and to examine associations between RFI, and blood metabolite profiles and feeding behavior traits to identify RFI biomarkers. Performance, dry matter intake (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). Low RFI steers consumed 17% less (P < 0.0001) DMI (9.05 vs 10.89 ± 0.14 kg/d), had 18% lesser (P < 0.0001) F:G (5.05 vs 6.11 ± 0.10) and generated $95 per head more (P < 0.001) profit compared to high-RFI steers, even though ADG and carcass value were not affected by RFI classification. Blood samples were collected from steers with lowest RFI (n = 25) and highest RFI (n = 24) on day 70 of the trial, and serum metabolite concentrations analyzed using ¹H-NMR spectroscopy. Partial least squares (PLS; MetaboAnalyst) were used to examine associations between RFI, and metabolites and feeding behavior traits. Of the 12 feeding behavior traits evaluated, 4 traits had variable of importance in projection (VIP) scores > 1.0, which included head-down (HD) duration, bunk visit (BV) duration, non-feeding interval (NFI) duration, and head-down to meal duration ratio (HD:MD). The first 2 components of PLS accounted for 54% of between-animal variance in RFI. Steers with low RFI had longer (P < 0.001) NFI duration (less time at the bunk), 45% lower HD duration, 35% lower BV duration, and 32% lower HD:MD ratio than high RFI steers. Of the 44 metabolites detected by ¹H-NMR, 5 metabolites had VIP scores > 2, which included glycine, betaine, tyrosine, valine, and leucine. The first 2 components of PLS accounted for 34% of between-animal variance in RFI. Steers with low RFI had higher (P < 0.001) concentrations of glycine, and lower (P < 0.06) concentrations of betaine, tyrosine, valine, and leucine than high-RFI steers. These preliminary results reveal that metabolomic profiling and feeding behavior traits may provide opportunities to identify biomarkers that are predictive of RFI in beef cattle. 

Keywords: feedlot cattle, metabolites, residual feed intake