Sources of variation of antimicrobial use in Charolaise and Limousine beef breeds in Veneto region (Italy)

The development of antimicrobial resistance is a growing problem which jeopardises both human and animal health. Livestock sector is generally blamed as principal contributor due to the over-use of antimicrobials to treat animals. Hence, new strategies to reduce antimicrobial use (AMU) are necessary. Little is still known on potential factors affecting AMU in beef production. Therefore, the objective of this study was to explore the impact of farm, breed, sex and season on AMU in Charolaise and Limousine breeds. Data on body weight, breed, sex and AMU were collected from 10 specialized beef farms (543 batches) located in Veneto region (Italy). Average daily gain (ADG) was calculated and AMU data were used to calculate a treatment incidence (TI100it) through the Defined Daily Dose Animal based on Italian dosage. An ANOVA was performed to investigate sources of variation of ADG and TI100it. Overall, farms differed significantly for both ADG and TI100it. The ADG was greater for Charolaise than Limousine breed (P <0.05). Limousine had greater TI100it than Charolaise (P <0.05), and males had greater TI100it than females (P <0.05), likely due to their higher susceptibility to respiratory diseases. Differences among seasons were also observed, with the coldest periods of the year having greater TI100it compared to summer and spring (P <0.05). Findings of the present study shed a light on potential risk factors of AMU in beef cattle, which will be useful to develop new strategies for the reduction of antimicrobials.