Effect of commingling animals at sorting facilities on performances and antibiotic use in beef cattle

The misuse of antibiotics in the animal sector is the main driver of antibiotic resistance. More than 80% of Italian beef cattle imported from France are Charolais, which undergo a commingling procedure before reaching Italian fattening farms. The aim of this study was to evaluate the effect of commingling Charolais cattle in France on antibiotic use (AMU) and animals’ performances in Italy. A total of 19,756 young bulls from 449 batches transported to Italy between 2016 and 2018 were considered. Carcase weight (CW), slaughter age (SA), antibiotic treatments, vaccinations information and the French department of origin were available for each animal. Also, treatment incidence 100 (TI100it) and average daily carcase gain (ADCG) were calculated. Three classes of commingling were assigned to each animal according to the French department of origin. A linear mixed model was used to investigate sources of variation of CW, SA, ADCG and TI100it. Respiratory diseases were the main reasons for treatment and macrolides were the most used class of antibiotics. The TI100it decreased by 11% from 2016 to 2018 (p <.05). Animals that went through the highest level of commingling had lighter CW, lower ADCG and greater TI100it than animals subjected to lower commingling (p <.05). Younger animals reached higher TI100it than older ones (p <.05). Younger and highly commingled animals had higher TI100it (p <.001) than older animals equally commingled. This first-of-its-kind study showed that commingling procedures increase the risk of AMU and affect the performances of Charolais cattle.