Predicting immunization status at arrival in Tennessee stocker calves

This study aimed to test if externally observed physical char­acteristics of calves on arrival at a stocker facility could be used to predict calfhood immunization status based on ob­served antibody titer levels. Knowledge of highly correlated features could allow stocker operators to mitigate the risk of bovine respiratory disease through informed buying practices and targeted management strategies, thus lowering morbidi­ty, mortality and treatment costs. Ear notches, blood and visu­al attributes were collected for 408 stocker calves at 4 farms in Tennessee. Each animal was tested for bovine viral diarrhea vi­rus-persistently infected status and titer levels for 3 viral agents that are present in most respiratory disease vaccines. Multiple visual characteristics were predictive of likely vaccination for BRD-causing agents, including the presence of a prior ear tag (1.6 times), castrated males (1.26 times), polled cattle (4.8 times), body condition score (1.46 times per full score), and being de­clared vaccinated or preconditioned (2.2 times). Additionally, we followed 60 calves through the stocker phase to ascertain how preconditioning affected downstream health events and performance. We found that preconditioned calves had lower BRD incidence, a higher occurrence of multiple detectible viral titers, and gained more weight over 56 days than did naïve cattle. Interestingly, many calves marketed as preconditioned did not have detectible viral titers on arrival. This work identifies informed, practical solutions and man­agement decisions for stocker operations when purchasing calves. It also lays the groundwork for future work identifying ways to deliver precision management to stocker cattle.