Assessing the Effectiveness of an Evidence-Based Algorithm for Antimicrobial Treatment in Neonatal Calf Diarrhea

Abstract: Background – Diarrhea is a major cause of mortality in calves, with antimicrobial drugs (AMD) being used in many cases. However, few guidelines for AMD use in calf diarrhea have been developed. Objectives – To evaluate the effectiveness of an evidence-based algorithm (EBA) for antimicrobial treatment of calf diarrhea. Animals – 106 neonatal calves. Methods – A blinded, non-inferiority, randomized controlled trial compared two treatments: (1) an EBA, in which calves were treated with AMD (trimethoprim-sulfadoxine 16mg/kg) only if they showed ≥2 of the following abnormalities: rectal temperature >38.8°C after anti-inflammatory medication (based on cut-off identified in a prior study), inability to stand, absent suckle reflex, sunken eyes, or scleral injection; and (2) a control group (CG), where all calves received AMD (trimethoprim-sulfadoxine) at diarrhea onset. All calves received enteral fluids for the duration of the diarrhea and meloxicam (0.5mg/kg) at the onset of disease. Cox survival analysis and logistic regression models assessed diarrhea duration, survival and the need for rescue treatment (i.e., additional AMD therapy). Results – In total, 40% (21/52) of the calves in the EBA group required AMD. Diarrhea duration was not different between groups (CG vs. EBA HR:0.78; 95%CI:0.52-1.16; P=0.22). Control calves had a trend toward higher mortality (OR:3.91; 95%CI:0.90-24.03; P=0.07) and more rescue treatments (OR:6.34; 95%CI:1.28-62.06; P=0.02) compared to EBA calves. Conclusions and Clinical Importance - The EBA did not affect diarrhea duration compared with the CG. However, the EBA trend for lower mortality risk suggests it may improve calf outcomes while reducing AMD use.