Health of finishing steers: Effects on performance, carcass traits, and meat tenderness

The impact of respiratory disease during a 150-d feedlot finishing period o n daily gain, carcass traits, and longissimus tenderness was measured using 204 steer calves. Feedlot health status was monitored in two ways. First, clinical signs of respiratory infection were evaluated each day; treatment with antibiotic was based on degree of fever (if rectal temperature exceede d 40 degrees C then calves were treated). Steers that were treated (n = 102 ) had lower (P < .05) final live weights, ADG, hot carcass weights (HCW), l ess external and internal fat, and more desirable yield grades. Steers that were treated had a higher prevalence of carcasses that graded U.S. Standar d than steers that were never treated. Second, as an alternative index of h ealth status, lungs of all steers were evaluated at the processing plant us ing a respiratory tract lesion classification system; this health index inc luded presence or absence of preexisting pneumonic lesions in the anteriove ntral lobes plus activity of the bronchial lymph nodes (inactive vs active) . Lung lesions were present in 33% of all lungs and were distributed almost equally between treated (37%) and untreated cattle (29%). Steers with lesi ons (n = 87) had lower (P < .05) daily gains, lighter HCW, less internal fa t, and lower marbling scores than steers without lesions. Compared to steer s with lesions but inactive bronchial lymph nodes (n = 78), steers with lun g lesions plus active lymph nodes had lower (P < .01) ADG and dressing perc entage. Longissimus sheer force values for steaks aged 7 d were lower (P = .05) from steers without lung lesions than those for steaks from steers wit h lung lesions. Overall, morbidity suppressed daily gains and increased the percentage of U.S. Standard carcasses. Compared to health assessment by cl inical appraisal (based on elevated body temperature), classification based on respiratory tract lesions at slaughter proved more reliable statistical ly and, thereby, more predictive of adverse effects of morbidity on product ion and meat tenderness.