sábado, 18 de maio de 2013
Cattle temperament, immunity and performance
Flighty cattle are difficult and sometimes dangerous to handle, and according to a report from USDA and university researchers, they could be better at concealing disease. According to a recent article in Agricultural Researchmagazine, from USDA’s Agricultural Research Service, reducing adverse consequences of stressful incidents and identifying animals that may react differently to stressors may benefit cattle’s growth and health.
The research team from the ARS Livestock Issues Research Unit in Lubbock, Texas, Mississippi State University and Texas AgriLife Research is studying interrelationships between stress and cattle temperament with transportation, immune challenges, and production traits. Their results so far indicate temperament plays a role in how cattle respond to those stressors.
The team tested Brahman calves shortly after weaning, when stress levels associated with weaning and transport typically are high. They first rated calves for temperament based on exit velocity from the chute, a method that objectively measures an animal’s fear or excitement by the speed at which it leaves the chute. They also used pen scoring, a more subjective method for grading cattle response to human presence in a pen setting. The researchers averaged exit velocity and pen scores to arrive at temperament categories including most calm, intermediate, and most temperamental.
The researchers then transported the calves 478 miles from Overton to Lubbock. After the trip, they drew blood samples and measured body temperatures before, during, and after administration of an endotoxin to simulate illness. Results showed that the endotoxin increased body temperature and induced secretion of epinephrine and cortisol, hormones associated with coping with stress. Visible signs of illness varied, however. The researchers observed and scored sickness behavior, and according to ARS animal scientist Jeff Carroll, the animals previously rated as calm showed noticeably greater signs of sickness, while the more temperamental animals continued to act high-strung and flighty. In a feedyard setting, animals that conceal signs of morbidity are less likely to receive treatment early, when it is most effective.
The researchers suggest 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 cows. “I’m not suggesting selecting for the calmest cattle,” says Texas A&M animal physiologist Ron Randel, “I’m suggesting that producers eliminate animals that are most temperamental to improve herd health and productivity, ensure animal welfare, and to protect animal and worker safety.”