Steers (n = 15,631) and heifers (n = 5,897) fed at 18 feedlots in southwest Iowa between 2002 and 2006 as part of the Tri-County Steer Carcass Futurity sponsored by Iowa State University were used to correlate various phenotypic traits with feedlot performance and carcass traits. Dependent variables (average daily gain, respiratory morbidity, hot carcass weight, fat thickness, calculated yield grade, marbling score, presence or absence of lung damage, loin muscle area and loin muscle area x100/HCW) were evaluated on the basis of initial body weight, disposition score (1 = calm, 6 = extremely excitable), muscle score, frame score, body condition score, number of treatments for respiratory disease, presence of lung lesions, breed makeup and percentage Angus genetics.

* Cattle with greater disposition score (more excitable) had lower initial body weight, final body weight, average daily gain, hot carcass weight, yield grade, quality grade, marbling score and mortality.

* Respiratory morbidity was negatively correlated with initial body weight, average daily gain, yield grade, hot carcass weight and marbling score.

* As initial BW increased, final body weight and hot carcass weight increased and respiratory morbidity decreased.

* Cattle with greater body condition score on arrival had greater initial body weight but were lighter at harvest.

* Increased number of treatments for respiratory disease was associated with lower average daily gain, greater mortality rate and greater incidence of lung lesions.

* Gain was similar between English- and Continental-breed cattle, although final body weight and hot carcass weight were greater and yield grade and yield grade-adjusted marbling score were lower for Continental-breed cattle.

* Cattle with a poor muscling score had lower hot carcass weight and loin muscle area and greater yield grade, marbling score and quality grade.

Animal disposition, health, breed type and frame score have dramatic effects on live feedlot performance and carcass traits.

Source: Reinhardt et al., Kansas State University, Manhattan, Iowa State University and Certified Angus Beef