Ronald M. Lewis
Date of this Version
Parham, J. T., 2018. Subjective measures of temperament in beef heifers are reliable indicators of physiological stress and indicate acclimation to repeated handling.
Associations between excitable temperament and many economically relevant traits have been established. In being heritable, temperament can be augmented through selection. Current methods to evaluate temperament in a production setting include numerous subjective and objective measurements, which some producers may find cumbersome to navigate. Those who utilize these methods may not do so efficiently if selection criteria are not indicative of an animal's response to stress, or initial evaluations are not strong indicators of future temperament. The objectives of this research were to develop a procedure for evaluation of calf behavior, indicative of physiological stress, and then determine whether stress will change under repeated and routine management as evaluated through behavioral and physiological measures. Each of three consecutive years, 20 commercial Bos taurus heifers, 2-wk post weaning, were randomly assigned to a factorial design of two measurement protocols [frequent (F), infrequent (IN)], and three recording periods, each 1 mo apart. The F measurements were collected over three consecutive days, and IN only on d 1, of a recording period. Heifers were calmly moved into a squeeze chute and their heads caught. Individuals assigned a chute score (CS) based on their reaction to 15 s of restraint. A fecal sample, heart rate, rectal temperature, and jugular blood sample were taken. Upon release, exit velocity (EV) over a 2 m distance was recorded, and an exit score (ES) assigned by the same individuals. Each heifers’ response to 30 s of exposure to a human stressor was then recorded both in an individual and group pen setting. An individual (IPS) and group (GPS) pen score was assigned. Scores ranged from 1 to 5 or 6, with increasing values indicative of more excitable (worsening) temperament. All subjective measures were reliably assessed. Moderate correlations existed between objective and subjective measurements of temperament, indicating they were representative of physiological stress. Furthermore, CS and IPS decreased considerably over time, especially in F heifers, as they acclimated to novel handling experiences. Producers may avoid unnecessarily culling cattle based strictly on initial response to novel stimuli by allowing acclimation to handling before assessing docility.
Advisor: Ronald M. Lewis