Is residual feed intake related to the feeding behavior of Nellore cattle during the four periods of the day?

The aim of this study was to evaluate feeding behavior traits across four time periods of the day and their relationship with residual feed intake (RFI) in uncastrated Nellore males. Records from 346 Nellore animals born from 2013 to 2016 and in 2019, which were submitted to feed efficiency tests at approximately 267±30 days of age in collective pens equipped with electronic feed bunks (GrowSafe®), were available. For the analysis, two experimental groups were selected based on RFI: low-RFI (RFI = -0.698±0.39 kg dry matter/day; n = 107) and high-RFI (RFI = 0.711±0.38 kg dry matter/day; n = 104). The feeding behavior traits, including dry matter intake (DMI, kg), meal duration (MD, min), frequency of visits (FV, number) and feeding rate (FR, kg/min), were evaluated across four periods of the day [dawn (00:00–05:59 h); morning (06:00–11:59 h); afternoon (12:00–17:59 h); night (18:00–23:59 h)]. Statistical mixed models included classificatory fixed effects of test groups, RFI groups, periods of the day (period), and the interaction between RFI groups x period, and the linear effect of the age at the start of the test. Repeated measurements of the same animal (period) were modeled by a proper residual (co)variance structure. The phenotypic values of DMI (2.91±0.03 kg), MD (51.5±0.62 min), FV (10.8±0.16 no.), and FR (0.058±0.0005 kg/DM) were higher (P < 0.05) in the afternoon. DMI and MD were lower in the low-RFI group compared to the high-RFI group (P < 0.05). Nonetheless, FV and FR were higher in the low-RFI group (P < 0.05). Additionally, DMI was lower during the morning, afternoon, and night periods in the low-RFI group (P < 0.05). Thus, the low-RFI group exhibited lower MD and FR during all periods (P < 0.05); however, FV was higher in these animals in the early morning and at night (P < 0.05) when compared to the high-RFI group. The results demonstrated that feed efficiency is related to the feeding behavior of Nellore cattle during the different periods of the day.