Risk factors for mid- and late-feeding-stage bovine respiratory morbidity and mortality based on individual animal treatments of beef feedlot cattle

Abstract

Previously published research on bovine respiratory disease (BRD) has emphasized the initial portion of the feeding phase; yet, little work has investigated risk factors associated with BRD incidence later in the feeding period. Our study objective was to identify risk factors associated with BRD morbidity and mortality timing within the feeding phase. Individual animal records for first BRD treatment (n = 188,437) or BRD mortality (n = 13,991) were classified as early stage, middle stage, or late stage based on the percentage of their cohorts’ feeding phase that was complete at day of event (event days on feed/cohort total days on feed). There were 141,097 early stage, 33,871 middle stage, and 13,469 late stage at first treatments for BRD and 7,821 early stage, 3,625 middle stage, and 2,545 late stage at death. Two ordinal logistic regression models (morbidity, mortality) were used to evaluate the association of cattle demographic factors (arrival weight, arrival lot size, sex, metaphylaxis, quarter of arrival) and the probability of an individual animal first treatment for BRD or mortality from BRD being early, middle, or late stage. All 2-way interactions of cattle demographics for morbidity were significant (P < 0.05), whereas for mortality, main effects of arrival weight and metaphylaxis were significant (P < 0.05) and only the 2-way interactions of sex by quarter of arrival and sex by lot size were significant (P < 0.05). In general, heifers, heavier animals at arrival, and cattle that arrived at the yard in the first and second quarter were the most likely demographic categories to have an initial diagnosis of BRD in the mid or late stage of the feeding phase.