119 Plasma metabolomics and feed behavior patterns in feed efficient or inefficient beef bulls

Abstract Residual feed intake (RFI) is a measure of feed efficiency (FE). Differences in plasma metabolites concentration found in animals with contrasting RFI are potential biomarkers of FE. Furthermore, feed behavior patterns could also be used to identify animals with contrasting RFI. We hypothesize that the integration of plasma metabolomics data and feed behavior can predict the future animal performance. We used 302 bulls subjected to an ad libitum diet for 56-d while allocated in pens equipped with GrowSafe System to evaluate RFI. Blood samples were collected for metabolomics analysis at the beginning (d 0) and at the end (d 56) of the trial. Feeding behavior metrics including feeding bout (FB), and eating time were estimated. Subsequently, the bulls were classified as low RFI (LRFI) and high RFI (HRFI). The performance test showed no differences between LRFI and HRFI animals in the initial body weight (LRFI: 408.62 ± 47.43 Kg; HRFI: 407.64 ± 60.22; P = 0.41), final body weight (LRFI: 510.33 ± 58.28; HRFI: 500.82 ± 72.23; P = 0.46), and average daily gain (LRFI: 1.67 ± 0.28; HRFI: 1.54 ± 0.36; P = 0.42). But the dry matter intake was less for LRFI (6.45 ± 1.78) in comparison with HRFI animals (8.81 ± 2.63; P 0.001). Metabolomics analysis performed on the top and bottom 30 bulls based on RFI, reveled increased concentrations of 18 metabolites in LRFI bulls on d 0, and 12 different metabolites on d 56. Among these compounds, Cer(d18:1/23:0) level was statistically greater on both d 0 (LRFI: 0.233 ± 0.016 µM; HRFI: 0.187 ± 0.014 µM, P = 0.039) and d 56 (LRFI: 0.267 ± 0.016 µM; HRFI: 0.205 ± 0.013 µM, P = 0.02), emerging as a potential biomarker distinguished by the multivariate analysis, capable of discerning between LRFI and HRFI animals. On the other hand, FB (LRFI: 13 events/d; HRFI: 15 events/d; P = 0.019) and eating time LRFI: 119 min/d; HRFI: 153 min/d; P 0.001) were different between the two groups. The more efficient animals (LRFI) were observed to visit the feed bunk less frequently and spend less time consuming feed compared with the less efficient animals (HRFI). In conclusion, further exploration of the metabolites’ pathways and their roles and recognition of feeding behavior patterns could provide valuable insights into the mechanisms contributing to FE.