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Tuesday, April 2, 2013
Temperament in cattle can be defined as reactivity or fear response to humans or handling. Terms used to describe temperamental animals include "flighty," "excitable," and "high strung." These animals can potentially injure themselves or their handlers.
There are numerous stressful routine events that cattlemen may not consider stressful–weaning, transportation, social mixing, and vaccination. These routine management practices have been shown to increase the secretion of cortisol and epinephrine. Cortisol and epinephrine are stress-related hormones.
The concern with increasing stress in livestock is that stress can negatively affect growth, reproduction, welfare, and immune function–predisposing cattle to infectious intestinal and respiratory diseases that cost U.S. cattle producers an estimated $500 million per year. Reducing adverse consequences of stressful incidents and identifying animals that may react differently to stressors may benefit cattle's growth and health.
Researchers are studying interrelationships of stress and cattle temperament with transportation, immune challenges, and production traits. They have found that, depending on temperament, cattle respond differently.
The scientists looked at exit velocity from the chute (The rate at which an animal exits a squeeze chute or scale box where it's been restrained or held after transport. A fast exit indicates the animal is showing fear and is stressed by handling and human activity.) and pen scoring (A subjective measurement in which small groups of cattle are scored based on their reactions to a human observer. Scores range from 1–calm, docile, and approachable, to 5–aggressive and volatile). The exit velocity and pen score for each animal were then averaged together to come up with a temperament score.
In the study, Brahman calves were classified by temperament and transported 478 miles from Overton to Lubbock. After the trip, blood samples and body temperatures were taken before, during, and after administration of an endotoxin to simulate illness. Sickness behavior was scored on a 1-to-5 scale that measured the severity of calves' behavioral responses to the challenge. A score of 1 indicated normal maintenance behaviors, and 5 indicated the greatest amount of sickness behaviors, such as head distension, increased respiration, and labored breathing.
Scientist could immediately tell that the calm animals had been given an immune challenge, because they showed visual signs and became ill. The more temperamental animals continued to act high-strung and flighty after the endotoxin challenge. If a temperamental animal doesn't show signs of illness, managers might not realize that the animal is sick and needs treatment.
Blood samples taken revealed that the endotoxin increased body temperature and induced secretion of epinephrine and cortisol, hormones associated with coping with stress.
Transported animals become stressed which contributes to the incidence of disease. Therefore, identifying cattle that are more susceptible to stressors and subsequently have altered immune responses may help to reduce the impact of sickness after transport.
Previous studies indicate that human-animal interactions are probably the most stressful events that the majority of cattle encounter.
The duration of transportation is not the stressor, but rather the action of being handled and loaded into the trailer. If cattle are handled in an appropriate manner and given water and feed at no more than 12-hour intervals, then getting on and off the trailer is the major stressor.
While the handling process is more stressful for animals, transportation duration and conditions can have negative effects on intramuscular fat.
The combined effects of transportation and animal temperament on body composition traits were assessed. Ultrasound images of muscle ribeye area, rib fat, intramuscular fat, and rump fat were taken to evaluate and measure fat mobilization.Temperamental cattle appeared to use more fat stores when stressed. Also, as the hauling distance increased, the percentage of intramuscular fat decreased.
Results show that temperamental cattle require special management practices to reduce stress before, during, and after transportation. Also, because temperament and resistance to bovine respiratory disease are both heritable traits, future research will include developing gene-based methods to select calm, stress-tolerant, and disease-resistant cattle.
In the meantime, cattle producers can use temperament scoring to select calmer bulls for breeding less temperamental cattle and use pen scoring for replacement females to eliminate the more temperamental cowss.