Risk factors associated with antimicrobial treatment incidence, average daily weight gain and mortality in Bavarian calf weaning operations.

Calf weaning operations represent a specialized segment of beef production in Southern Germany which manage the critical transition period from milk feeding to complete weaning. These farms face challenges comparable to those encountered by veal and beef enterprises in establishing optimal housing and management conditions that ensure both animal welfare and economic viability. The present explorative study aimed to identify management-, housing-, and environment-related risk factors associated with antimicrobial treatment incidence (TI), average daily gain (ADG), and mortality in 53 Bavarian calf weaning operations. Data sources included: (1) a structured questionnaire covering calf purchase, arrival management, feeding, housing, treatment protocols, and prophylaxis; (2) antimicrobial usage and growth performance records; and (3) standardized on-farm assessments of housing conditions and clinical examinations of 1,060 calves. Median TI was 14.0, median ADG 1,121g/day, and median mortality 1.0%. Higher TI was significantly (P < 0.05) associated with a higher number of fattened calves per year, shared utensils between calf groups, and the presence of moderately impaired subjective air quality, whereas higher relative humidity was associated with decreased TI. Implementation of an all-in/all-out system was associated with lower mortality. Higher ADG was associated with larger herd size and the absence of a bedded lying area, whereas poor hygiene was associated with lower ADG. These findings provide a basis for future prospective studies and evidence-based recommendations aimed at optimizing housing and management practices to improve animal welfare, reduce antimicrobial use, and enhance economic performance in these specialized calf weaning operations.