AMES, Iowa -- The disposition of beef cattle has long been considered by producers as a ‘convenience’ trait which impacts the handling of cattle and the safety of workers as well as the animals themselves. Research has shown that disposition is a heritable trait that can be improved by proper culling strategies.
Research also has shown the impact of disposition on performance and carcass bruising, but virtually no data exists on its impact on quality grade. As a result, researchers at Iowa State University (ISU) set out to determine the effect of disposition of beef calves on feedlot performance, carcass quality grade and economic return.
Darrell Busby, ISU Extension beef field specialist, explains how the research was conducted. “A total of 13,315 beef calves from eight Iowa feedyards were monitored during the feedlot period for feedlot gain and carcass quality. The calves were weighed upon arrival, after 35 days, at re-implant, and prior to harvest. Quality grade information was taken at the time of harvest.”
“To measure disposition, we used the Beef Improvement Federation’s Six Point Scoring System, and each animal was assigned a score at test weighing, re-implant time and pre-harvest.” The six point scoring system rates cattle at scores from 1 to 6, 1 for docile and 6 for very aggressive.
The disposition scores were averaged to calculate a mean disposition score, which was used to classify calves into three groups for analysis: 1 and 2 = docile; 3 and 4 = restless; and 5 and 6 = aggressive. The 13,315 calves were tallied as 9,642, 2,915 and 758 in the docile, restless and aggressive categories, respectively. The arrival weight, average daily gain (ADG), morbidity rate, acceptance rates for Certified Angus Beef® (CAB), and percent Prime, Choice, Select and Standard of each animal were then compared across all three groups.
“Disposition of calves can clearly impact feedlot performance with an even greater impact noted on carcass quality grade,” says Daryl Strohbehn, animal science professor at ISU. “The group categorized as ‘docile’ outshined the restless and aggressive groups in all the performance and carcass quality categories.”
Arrival weight (lb) and ADG (lb/day) were 630.5 and 3.17; 626.4 and 3.11; and 610.8 and 2.91 for docile, restless and aggressive calves, respectively. The percent Prime carcasses for docile, restless, and aggressive calves were 1.69, 1.17, and 0.13, respectively, while the percent Choice carcasses for docile, restless, and aggressive calves were 72.45, 67.91, and 58.12. In fact, nearly 42 percent of the aggressive calves were graded as Select or lower, compared to less than 26 percent of docile calves.
Acceptance rates for black-hided Angus-type calves eligible for the CAB program were 29.07 percent and 22.83 percent for docile and restless calves, and only 14.31 percent for aggressive calves.
“Some difference in reduced feedlot performance and carcass quality traits existed between cattle classified as docile and restless, but the greatest effect was in calves scored aggressive in behavior,” notes Strohbehn. When compared to docile calves, the feedlot gain was reduced by approximately 0.3 pounds per day, and the mortality rate nearly doubled for calves with aggressive behavior.
“All in all, docile calves returned $62.19 per head more than aggressive calves, which can greatly impact a producer’s bottom line.”
For more information about the research, visit http://www.ans.iastate.edu/report/air/2006pdf/R2070.pdf.
Rachel E. Martin,