Effect of Disposition on Feedlot Gain and Quality Grade

A total of 13,315 beef calves fed at eight Iowa feedyards were used to evaluate the effect of disposition during the feedlot period on feedlot gain and carcass quality. The calves, representing 12 states, were consigned to the Iowa Tri-County Steer Carcass Futurity and were weighed upon arrival, after 35 days, at reimplant, and prior to harvest. A disposition score (Beef Improvement Federation Six Point Scoring System – 1 = very docile and 6 = very aggressive) was assigned at on test weighing, re-implant time, and pre-harvest, and these disposition scores were averaged to calculate a mean disposition score. The mean disposition score was used to classify calves into three groups for analysis – 1 and 2 = docile (n=9,642), 3 and 4 = restless (n=2,915), and 5 and 6 = aggressive (n=758). A common diet and health program was utilized at each feedlot. Calves were sorted and harvested when they were visually evaluated to have 0.4 inches of fat cover. 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. Morbidity rate was significantly (P=.0009) affected by disposition class 19.23, 16.82 and 16.18% for docile, restless and aggressive calves, respectively. However, disposition score did not affect mortality rate (P=.1985). The percent prime, choice, select, and standard carcasses for docile, restless, and aggressive calves were 1.69, 72.45, 23.29, and 2.55; 1.17, 67.91, 27.49, and 3.43; and 0.13, 58.12, 36.20, and 5.55, respectively. Disposition score influenced the percentages of carcasses in each quality grade (P<.001). Acceptance rates for black-hided Angus-type calves eligible for the Certified Angus Beef ® Program (CAB) were 29.07, 22.83, and 14.31 (P<.0001) for docile, restless, and aggressive calves, respectively. When considering the effect of disposition on quality and yield grade, feedlot gain, death loss, and treatment costs, docile calves returned $62.19/head more than aggressive calves. Calves with poor disposition were lighter upon arrival at the feedlot, gained less, had reduced quality grade, and reduced CAB acceptance rates compared with docile calves.