Johnson, Jocelyn Rose (2019-07). APPLICATION OF CHEMOMETRICS TO PREDICT INTAKE AND FEED EFFICIENCY USING FEEDING BEHAVIOR PATTERNS IN GROWING CATTLE. Doctoral Dissertation.
Residual feed intake (RFI) is an ideal trait for use in selection programs to improve feed efficiency in beef cattle, as it quantifies between-animal variation in DMI that is independent of body size and productivity, to better reflect inherent differences in biologically relevant processes associated with feed efficiency. RFI is an expensive phenotype to measure and thus there is need to identify biomarkers to more cost effectively predict genetic merit for RFI. Objectives of this study were to characterize feeding behavior patterns of cattle with divergent RFI phenotypes and to evaluate the accuracy of using feeding behavior traits to predict individual-animal RFI and DMI. Performance, DMI, and feeding behavior data were collected from 498 Angus-based composite steers (Study 1), 408 heifers (Study 2) and 321 steers (Study 3) comprised of Brangus, Braford, Simbrah, and Angus breeds, and 1,787 Holstein heifers (Study 4). DMI and feeding behavior traits were measured using a GrowSafe System, and RFI calculated within trial. Nineteen feeding behavior traits were evaluated: Frequency and duration of bunk visit (BV) and meal events, head-down duration (HDD), average meal length, maximum non-feeding interval, corresponding day-to-day variation (SD) of these traits, and ratios of HDD per BV duration, HDD per meal duration, and BV events per meal event. Consistently, low-RFI animals consumed 16 to 24% less DMI, had less day-to-day variation in DMI, fewer and shorter BV events, and less HDD than high-RFI animals. Associations between RFI and meal traits were less consistent across studies, as individual-animal meal criterion values were higher for low-RFI Angus-composite steers and Holstein heifers, but were not different for mixed-breed steers and heifers, compared to high-RFI animals. However, meal duration was lower for low-RFI animals compared to high-RFI animals across studies. Across studies, low-RFI animals had less day-to-day variation in feeding behavior patterns than high-RFI animals. Between-animal differences in feeding behavior patterns accounted for 35 to 47% of the variation in RFI, and 17 to 29% of the variation in DMI independent of mid-test BW0.75 and ADG. Ongoing development of biosensor-based technologies to quantify feeding behavior patterns will provide opportunities to more accurately predict DMI in support of precision-nutrition strategies, and to more cost effectively select more feed-efficient cattle.