Relationship between current temperament measures and physiological responses to handling of feedlot cattle
Williams, Andrew Fillmore.
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Temperament in beef cattle has become a research focus due to increasing consumer awareness of animal welfare. Researchers have defined temperament as behavioral responses to a perceived stressful event. "Fight-or-Flight" response is influenced by environmental and genetic factors including age, sex, and breed. Subjective chute scoring systems have been used by many researchers. Due to the subjectivity and associated variability among observers, chute scores have been questioned for repeatability and consistency. An alternative measurement currently used, is exit velocity or speed at which an animal exits a chute, and is recognized as the most practical objective measure for assessing temperament. Physiological markers used to evaluate temperament are increased blood cortisol and lactate concentrations. The first objective of this study was to compare temperament differences between feedlot steers and heifers. The second objective was to evaluate physiological measures taken chute side as potential markers for defining an animal's temperament and potential predictor. Pulse, oxygen saturation, rectal temperature, blood lactate, blood glucose and lactate concentrations, salivary cortisol, and serum cortisol were measured on mixed breed and sex feedlot cattle (n = 197), significant difference alpha = P< 0.05 . Exit velocities were used to classify animals as fast, medium, and slow, plasma lactate was significantly different between all classes. Exit velocity and physiological measures differed between sex. Heifers had higher exit velocities (P = 0.003), plasma lactate concentrations (p = 0.03), and cortisol concentrations (P = 0.001). Simple correlations among these variables showed rectal temperature (heifers r = 0.44, P <0.0001; steers 0.45 P < .0001), plasma lactate (heifers r = 0.52 P < 0.0001; steers r = 0.63 P < 0.0001), serum lactate (heifers r = 0.53 P < 0.001; steers r = 0.59 P < 0.001) and glucose (heifers r = 0.54 P < 0.001; steers r = 0.32 P <0.003) were all correlated to exit velocity in both sexes. Cortisol measures were not correlated to exit velocity in steers but were in heifers. Linear models were constructed and evaluated using Akaike information criterion, the top candidate model was plasma lactate in combination with body temperature to predict exit velocity.