A novel objective chute score interacts with monensin to affect growth of receiving cattle.

Growth in cattle may be related to animal temperament via alterations in intake or feed conversion. However, temperament is ill-defined, and different temperament measures may relate differently to production traits or interact with dietary factors in their effects. To examine relationships between diet, temperament, growth, and health, 160 crossbred steers (262 ± 22 kg) were used in a 56-d RCBD experiment with a 2 × 2 × 2 factorial treatment structure with 5 pens/treatment. Steers were pen fed a corn silage-based diet with or without monensin (41.9 g/t DM), ad libitum. Temperament treatments (assigned on d -7) were exit velocity (EV; slow vs. fast) and objective chute score (OCS; low vs. high), a novel temperament measure, representing the CV of weights collected at 5 measures/s for 10 s while an animal's head was restrained in a chute. Both were measured on d -7, 0, 14, 28, 55, and 56. Subjective chute scores (SCS; visual estimates of animal activity obtained simultaneously with OCS measures) were measured on d -7 and d 56. Jugular blood samples from d 28 were analyzed for antibody response to leptospirosis vaccine and NEFA concentrations. No monensin × OCS × EV interactions were detected ( ≥ 0.11). There was a positive correlation between SCS and OCS ( < 0.01; = 0.57). Changes in OCS and EV across the duration of the study differed among treatments (treatment × day, < 0.10) and indicated that initial measures may be better proxies of growth than average measures. There were no interactions between EV and OCS ( ≥ 0.15) for any response variable and no interactions among treatments ( ≥ 0.31), nor main effects of temperament factors ( ≥ 0.12) for DMI (%BW). Monensin decreased DMI ( < 0.01) similarly across all levels of EV and OCS. Gains and G:F responses to monensin depended on OCS ( < 0.10) but not EV ( ≥ 0.80). Gain was reduced ( < 0.10) by monensin with low, but not high, OCS, and G:F was increased ( < 0.10) by monensin on high, but not low, OCS. Gain during the second 4 wk was lesser ( = 0.04) in fast, compared with slow, EV animals. Results provide novel indications that certain temperament measures can interact with dietary manipulation to influence animal performance.