Olson, Cameron Alexander (2017-08). The Effect of Temperament at Feedlot Arrival on Growth Efficiency, Feeding Behavior, and Carcass Value in Beef Heifers. Master's Thesis.
Temperament of cattle is defined as the animal behavioral response to humans. Objectives of this study were to evaluate the effects of temperament and breed type (Angus, Braford, Brangus, and Simbrah) on productivity, feed intake and efficiency, feeding behavior patterns and carcass-quality traits in finishing heifers. In 3 trials, heifers (N = 415, BW = 280 kg) were fed a high grain diet in pens equipped with electronic feeders to measure DM intake and feeding behavior traits. Heifers were slaughtered at a backfat thickness of 1.2 cm, and data collected to determine yield and quality grades. Warner-Braztler shear force was measured on steaks at 1- and 14-d post-mortem aging. Residual feed intake (RFI) was calculated as the residual from regression of DMI on mid-test BW0.75 and ADG. Relative exit velocity (REV) was recorded at feedlot arrival and used as a covariate in Mixed models to assess the effects of temperament and interactions with breed on response variables. Calm heifers had 4% heavier initial BW, gained 12% more per day, consumed 8% more DMI per day and had 4% more favorable G:F than excitable heifers. There was a temperament x breed interaction (P < 0.01) for RFI, whereby DMI per BW0.75 and RFI decreased as REV increased in Braford heifers but not in heifers of the other 3 breeds. Calm heifers had 10% greater head-down duration, 9% greater bunk visit (BV) duration, and had 11% shorter time-to-bunk than excitable heifers. Calm heifers had 9% greater meal duration, and consumed meals that were 22% longer and 17% larger compared with excitable heifers. Frequency of BV and meal events were not affected by temperament, but calmheifers had 12% more BV events per meal then excitable heifers. Carcasses of calm heifers were 4% heavier, had 7% greater BF depth, and 4% higher YG than carcasses of excitable heifers. Steaks from calm heifers were more tender then steaks from excitable heifers. Based on a carcass grid that accounted for tenderness-value differences, calm heifers generated $62 more income then excitable heifers, demonstrating that temperament is an important economically relevant trait. Systems that sort calves based on temperament into targeted production-outcome groups, could reduce within-group variation in production efficiency and carcass quality, adding value to the beef production chain.