Technical note: Exit velocity as a measure of cattle temperament is repeatable and associated with serum concentration of cortisol in Brahman bulls.
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The objectives of this study were 1) to compare temperament assessments, using multiple techniques and over repeated observations, to gauge temperament over the long-term and 2) to evaluate the relationship of the temperament appraisals with serum concentrations of cortisol (CS). Measures of temperament were gathered over 3 repeated observations (60-d interval) of yearling, fall-born Brahman bulls (initial BW = 320 +/- 4 kg; n = 66). Temperament assessments included exit velocity (EV), which was the rate at which the bulls exited the squeeze chute and traversed a fixed distance (1.83 m); pen scores (PEN; 1 = quiet to 5 = excited), ascertained from animal behavior while penned in small groups (n = 5); and chute scores (CHUTE; 1 = quiet to 5 = excited), determined from behavioral responses to restraint on the weigh scale. Temperament measures obtained during the initial data collection (d 0) were all positively correlated (r > or = 0.35, P < 0.005) with one another. Additionally, PEN (r = 0.29, P < 0.05) and EV (r = 0.26, P < 0.05) were positively correlated with CS, whereas CHUTE was not (r = 0.09, P = 0.46). All serial EV measures were positively correlated (r > 0.31, P < 0.02). All PEN were positively correlated (r > 0.31, P < 0.01), whereas serial measures of CHUTE were not (P > 0.3). Exit velocity was positively correlated with CS within d 0 (r = 0.26, P = 0.04) and 120 (r = 0.44, P < 0.01). The EV data obtained at d 0 were transformed into a discrete variable, EV ranking (EV RANK; 1 to 3 scale), in which 1 equated to <1 SD below the mean and 3 equated to >1 SD above the mean. Mean EV (P < 0.01) decreased from d 0 (2.82 +/- 0.07 m/sec) to 120 (2.11 +/- 0.10 m/sec). Time also influenced (P < 0.01) CS; mean CS decreased between d 0 (14.6 +/- 0.7 ng/mL) and 120 (11.1 +/- 0.8 ng/mL). Measures of EV can be a valuable tool for the assessment of cattle temperament and a possible predictor of temperament and stress responsiveness to future animal handling events.
