Cattle producers and caretakers are probably familiar with the ‘fight or flight’ concept, which is the ability of an animal to react quickly to a real or perceived threat (stressor). The manner in which cattle react to threats, humans, a fearful situation or a novel, stressful environment, is its temperament.
Temperament of cattle is a topic of increasing interest to the U.S. beef industry because of its negative relationship with animal wellbeing, health and productivity. Temperamental cattle can be excitable, stress responsive or wild and may injure their caretakers, other cattle or themselves, and they may damage facilities. Temperament is a heritable trait; therefore the beef industry may apply selection tools to improve their herds, protect animal wellbeing and enhance profitability.
For these reasons, the genetic basis, physiological mechanisms and practical impact of temperament and stress responsiveness continue to be investigated by Texas A&M AgriLife Research and Extension personnel in the Department of Animal Science.
Newborn Brahman calves that are prenatally stressed are less competent to survive bacterial disease than non-stressed calves.
Dr. Ron Randel, professor, regents fellow and senior AgriLife Research faculty fellow stationed in Overton, and Dr. Tom Welsh, professor and AgriLife Research faculty fellow, are two of the scientists in the Department of Animal Science who investigate the influence of stress and temperament on performance of beef cattle. Their research team has studied these relationships in weaning age cattle, and is currently studying the effect of prenatal stress on postnatal temperament, health and performance of beef calves.
Temperament and stress: definition and relationship to cattle management
Temperament is defined as the manner in which cattle respond to humans, a fearful situation or a novel environment. Stress is defined as the instance when animals make physiological or behavioral adjustments to cope with a stressor.
“The stress response helps an animal maintain balance or homeostasis. Temperamental animals are more stress responsive than their calmer herd mates,” Welsh explained.
Many production practices such as weaning, ear tagging, branding, castration, vaccination, social mixing, and transportation can be stressful for cattle, Randel said. Furthermore, temperamental cattle have reduced growth rates, carcass traits and immune function.
“Reduction of stress in a herd of cattle should result in improved productivity and profit. Selection of cattle with more easily managed temperaments will result in less stress as well as reduced risk in handling the cattle for routine management,” Welsh said.
Evaluation of temperament and stress responsiveness
To study temperament, the Randel-Welsh team used the pen score and exit velocity methods. Pen score is a subjective method to measure a calf’s reactivity to a human observer and is ranked on a scale of 1 (described as calm, docile and approachable) to 5 (described as volatile, very aggressive and wild). Exit velocity, the rate at which a calf traverses a defined distance of 6 feet after exiting a working chute, provides the team with an objective measure of temperament.
Through collaboration with Dr. Rhonda Vann at Mississippi State University and Dr. David Riley, associate professor of animal breeding and genetics in the Department of Animal Science at Texas A&M, the team documented that temperament and exit velocity are repeatable, moderately heritable traits. Hormone assay methods were used to demonstrate that the more temperamental cattle have greater peripheral blood concentrations of the adrenal gland derived stress-related hormones cortisol and epinephrine. Cortisol stimulates the production of glucose and stimulates the breakdown of muscle protein. Epinephrine (i.e., adrenaline) increases plasma concentration of glucose and non-esterified fatty acids by stimulating the breakdown of glycogen and triglycerides.
These hormonal and metabolic biomarkers have been positively correlated with subjective and objective measures of temperament in beef calves from birth to weaning age in studies conducted by Randel and Welsh and their collaborators, Vann at MSU and Dr. Jeff Carroll and Dr. Nicole Burdick with USDA ARS Livestock Issues Research Unit in Lubbock. The team uses these methods to study temperament’s association with health and performance traits of growing calves.
Temperament’s association with performance and health traits
Randel and Welsh graduate students conducted a series of collaborative studies with Department of Animal Science, Texas A&M University-Kingsville, USDA ARS Clay Center and Lubbock, Texas A&M College of Veterinary Medicine and Biomedical Sciences, Mississippi State University, Texas Tech University and Texas A&M AgriLife Extension personnel to study temperament’s association with performance and health traits of beef calves. They determined that stress-responsiveness and temperament at weaning were negatively associated with post-weaning immune function, feed intake and carcass traits.
Prenatally stressed suckling calves are more temperamental than their non-stressed herdmates.
For example, Welsh said temperamental steers had higher concentrations of stress-related hormones and a lesser degree of dry matter intake which was suggestive of a negative effect of temperament on feeding behavior. Also, the more temperamental steers yielded less tender carcasses (based on increased shear force) and temperamental cattle had less fat stores (marbling, indicative of a negative effect on quality grade).
Temperament may affect white blood cells and influence susceptibility to viruses and bacteria.
Specifically, lymphocytes of temperamental calves produced less antibody relative to calm calves after vaccination at weaning time. Recent studies indicate that white blood cells of temperamental calves have less bactericidal activity than those from calm calves from 24 hours to 6-to-9 days post-weaning which may make these stress responsive calves more susceptible to pathogenic bacteria.
The team, in conjunction with Dr. Sara Lawhon, veterinary pathobiology, now studies the influence of temperament on susceptibility to enteric diseases and shedding of Salmonella typhimurium and E. coli in weaned calves.
Effect of prenatal stress on postnatal temperament, performance and health
Randel has stated that “One’s health begins in utero,” therefore, new projects focus on the impact of prenatal stress on postnatal stress responsiveness, temperament, immunity, feeding behavior, and metabolism of young cattle from birth to weaning age.
The Randel-Welsh team recently found that prenatally stressed neonatal calves are more temperamental and have alterations in immune characteristics and energy metabolism that may negatively affect growth and health.
The Randel-Welsh team is one of several research groups within the Department of Animal Science that studies trans-generational metabolomic and health effects of prenatal stress. This topic is relevant as more evidence accumulates that postnatal health and productivity are affected by prenatal experiences. Determining the physiologic and genetic mechanisms that control temperament and stress responsiveness should improve animal wellbeing and enhance profitability in the beef industry.
-30-
For more information regarding news from the Department of Animal Science, College of Agriculture and Life Sciences, Texas A&M University, please contact Courtney Coufal at cacoufal@tamu.edu or (979) 845-1542.