|Chase, Chadwick - Chad|
|Randel, Ronald - Texas Agrilife|
|Riley, David - Texas A&M University|
|Coleman, Samuel - Former ARS Employee|
|Phillips, William - Former ARS Employee|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/16/2017
Publication Date: 12/1/2017
Publication URL: http://handle.nal.usda.gov/10113/5922763
Citation: Chase, Jr., C.C., Randel, R.D., Riley, D.G., Coleman, S.A., Phillips, W.A. 2017. Evaluation of tropically adapted straightbred and crossbred beef cattle: Cortisol concentration and measures of temperament at weaning and transport. Journal of Animal Science. 95(12):5253-5262. https://doi.org/10.2527/jas2017.1924.
Interpretive Summary: Efficient beef cattle production may only be realized when stressors are minimized. Some stressors are associated with the normal production cycle, e.g., weaning and transport. Circulating concentrations of cortisol are generally used as an indicator of stress response. Temperament (the response of an animal to handling by a human) is also an important trait not only for productivity of the animal but also safety of the animal and handler. A new tool that is an objective measure of temperament is termed exit velocity. Other subjective measures of temperament include chute score and pen score. Breedtype differences in stress response and temperament may exist, as well as, at different times during the normal production cycle. This research evaluated Angus, Brahman, and Romosinuano straightbred and crossbred calves at weaning (n = 993) and steer calves at transport (Florida to Oklahoma; n = 471). Cortisol concentrations at weaning were highest 24 hours after weaning. Cortisol concentrations at weaning and transport did not differ among straightbreds or among crossbreds. Concentrations of cortisol at weaning and transport for straightbreds were numerically ranked Romosinuano, Brahman, and Angus from highest to lowest, respectively. Assessment of temperament using the objective measurement of exit velocity or the subjective measures of chute score or pen score generally provided similar results: Brahman greater than Brahman crosses greater than Angus, Romosinuano, and their reciprocal crosses. For exit velocity, however, Brahman did not differ from Brahman crosses and Angus did not differ from Romosinuano or Brahman crosses. At transport, sire breed and dam breed affected exit velocity of steers with higher estimates for Brahman than Romosinuano or Angus. Heterosis for Brahman-Angus was significant and positive for cortisol concentration and all measures of temperament. Romosinuano tended to have the highest concentrations of cortisol, but lowest measurements for temperament. These results suggest that exit velocity offers producers an objective assessment of temperament that if conducted at weaning could allow selection of replacement animals with favorable temperaments.
Technical Abstract: The objective of this research was to evaluate circulating concentrations of plasma cortisol and measures of temperament at weaning in calves (steers and heifers) and at transport in steers. Calves (n = 993) were produced from a 3-breed diallel mating design that included calves from 3 consecutive years. Breed types of calves were straightbred Angus (A), Brahman (B), and Romosinuano (R) and all F1 crossbred combinations (AB, BA, AR, RA, BR, and RB). At weaning (d 0) and at 24 and 72 h after weaning, blood was sampled from calves and the plasma was stored for later cortisol assay. Additionally, at each of these times, temperament was assessed as chute score, exit velocity, and pen score. About 1 mo later, steer calves (n = 471) were sampled before shipment, at arrival, and at 24 h, 72 h, 2 wk, and 4 wk after shipment (2,025 km; Brooksville, FL, to El Reno, OK). At each of these sampling times, blood was collected and plasma was stored for subsequent cortisol assay and temperament was assessed by measurement of exit velocity. At both weaning and transport, plasma concentrations of cortisol did not significantly differ (P > 0.05) among straightbreds or among crossbreds. Significant (P < 0.05) positive genetic effects were observed for plasma concentration of cortisol at weaning (heterosis for BA and direct Romosinuano effect) and transport (heterosis for RA, BR, and BA; direct Romosinuano effect; and maternal Angus effect). Assessment of temperament using the objective measurement of exit velocity or the subjective measures of chute score or pen score (1 [lowest] to 5 [highest excitability] scale, based on behavior in chute and behavior in pen with human observer, respectively) generally provided similar results: Brahman was higher than Brahman crosses, which were higher than Angus, Romosinuano, and their reciprocal crosses. For exit velocity, however, Brahman did not differ from Brahman crosses and Angus did not differ from Romosinuano or Brahman crosses. At transport, sire breed and dam breed affected exit velocity of steers, with higher (P < 0.05) estimates for Brahman than for Romosinuano or Angus. These data suggest that weaned calves and shipped steers of various breed types show a similar response to stressors in cortisol concentration. In contrast, in assessing temperament or behavioral response to humans, Romosinuano and Angus had better temperaments and were less excitable than Brahman.