126 Temperament assessment at the feedlot: evaluation of changes in exit velocity, hematology, and serum biomarkers of cattle temperament in steers.

Abstract This study evaluated changes in exit velocity (EV), hematology parameters, and blood stress and metabolic markers as they relate to cattle temperament during the feedlot period in beef steers. Two hundred forty-five steers (248 ± 24kg) were received in two blocks at the Texas Tech University Burnett Center. Steers were processed on arrival (initial; d 0), interim (d 126 for Block 1, d 123 for Block 2), and final (d 252 for Block 1, d 242 for Block 2). At processing, body weight (BW) and EV was recorded, and blood samples were collected for serum isolation and hematology measurements. Exit velocity was the rate of speed of a steer traversing 2.37 m after exiting a working chute. Based on EV, steers were placed in temperament classifications [Calm (n = 47), Intermediate (n = 152), or Temperamental (n = 46)]. Using a subset of the 16 most Temperamental and 16 most Calm steers, serum was analyzed for glucose, non-esterified fatty acid (NEFA), cortisol, and lactate concentrations and complete blood count data were analyzed. The effect of temperament on EV, serum variables, and hematology were analyzed using the MIXED procedure of SAS, while the simple linear regression was used to evaluate changes in EV and BW. There was a temperament × time interaction (P < 0.01) for EV. Exit velocity decreased over time (P < 0.01) for Intermediate and Temperamental steers, while EV increased from initial to interim measurements before decreasing at the final measurement in Calm steers (P < 0.01). Exit velocity decreased as BW increased (P < 0.01). The EV of Temperamental steers decreased at a faster rate than Intermediate steers as body weight increased (P < 0.01), and the EV of Calm steers was not affected by changes in BW (P = 0.52). There was a temperament × day interaction (P ≤ 0.01) for hemoglobin and mean corpuscular volume, and a tendency (P = 0.06) for a temperament × day interaction for hematocrit, platelets, and percentage of monocytes. Also, red blood cells were greater while mean corpuscular hemoglobin was less in Temperamental than Calm steers (P ≤ 0.05). Serum cortisol, glucose, and lactate concentrations were greater (P < 0.01) in Temperamental than Calm steers, while NEFA concentrations were not affected by temperament (P = 0.54). Strong correlations were observed between BW and values of mean corpuscular volume and mean corpuscular hemoglobin (r = 0.78-0.78; P < 0.01), while there were moderate correlations between EV and red blood cells, glucose, and lactate (r = 0.44-0.52; P < 0.01). This study is one of the first to report effects of cattle temperament on hematology variables in steers during the feedlot period, and support previously reported serum biomarkers for temperament in cattle.