Residual feed intake (RFI) has gained attention as a measure of efficiency in feedlot cattle, and researchers continue to explore methods to characterize the trait.

Texas A&M University researchers Ira Parsons, Jocelyn Johnson, William Kayser, Luis Tedeschi and Gordon Carstens recently published a study in the Journal of Animal Science that examined feeding behavior patterns of steers with divergent RFI phenotypes.

Parsons et al. conducted three trials including 508 Angus-based composite crossbred steers — with an initial bodyweight of about 309 kg — fed a high-concentrate diet in pens equipped with electronic feed bunks.

The researchers collected initial and final carcass ultrasound measurements on days 0 and 70, and bodyweight was measured at 14-day intervals. Individual dry matter intake (DMI) and feeding behavior traits were collected for 70 days, they noted, and RFI calculated as the residual from the regression of DMI on average daily gain (ADG) and mid-test metabolic bodyweight.

Parsons et al. ranked steers by RFI and assigned them to low-, medium- and high-RFI classes based on +/-0.5 standard deviations from the mean RFI within the trial.

The feeding behavior traits evaluated in this study included frequency and duration of bunk visit and meal events, head-down duration, mean meal length, time-to-bunk interval, the maximum nonfeeding interval and the day-to-day variation of these traits, defined as the root mean squared error from linear regression of each trait on the day of trial, the researchers explained.

Additionally, three ratio traits were evaluated: bunk visit events per meal, head-down duration per bunk visit event and head-down duration per meal event.

According to Parsons et al., low-RFI (feed-efficient) steers consumed 16% less (P < 0.01) DMI, while bodyweight and ADG were not different compared with high-RFI steers.

Low-RFI steers also had 18% fewer and 21% shorter (P < 0.01) bunk visit events, and 11% fewer and 13% shorter (P < 0.01) meal events per day compared with high-RFI steers, Parsons et al. reported. Additionally, they said low-RFI steers exhibited less (P < 0.05) day-to-day variance in DMI and frequency and duration of bunk visits and meal events as well as head-down duration compared with high-RFI steers.

The researchers explained that the feeding behavior trait differences due to RFI were minimally affected by covariate adjustment for DMI, indicating that steers with divergent RFI have distinct feeding behavior patterns that are largely independent of differences in DMI.

Parsons et al. concluded that feeding behavior traits may be useful biomarkers for the prediction of feed efficiency in beef cattle.