# The effects of biotic treatments on degradation of antimicrobials and coccidiostats in broiler litter used as ruminant feed

## TL;DR

This study compares different low-cost methods to reduce drug residues in chicken litter used as cattle feed, finding that stacking is most effective.

## Contribution

First systematic comparison of stacking, aerobic, and anaerobic treatments for pharmaceutical residue degradation in broiler litter.

## Key findings

- Stacking achieved >95% degradation for key antimicrobials and 54.9–74.7% for coccidiostats.
- Stacking preserved high crude protein levels (32–34.8%) and reduced moisture by 29.5–34.6%.
- Aerobic treatment reached 60°C quickly, while stacking reached 50°C over 2 weeks, both outperforming anaerobic methods.

## Abstract

While broiler litter (BL) represents a valuable protein source for ruminant feed, the presence of pharmaceutical residues poses significant concerns for food safety and antimicrobial resistance. Previous research has primarily focused on composting and aerobic digestion of BL, leaving a critical knowledge gap regarding the comparative efficacy of economically viable treatment methods. This study presents the first systematic comparison of three cost-effective treatments—stacking, aerobic, and anaerobic processing—specifically analyzing their impacts on pharmaceutical compound degradation in BL intended for ruminant feed. Using LC/MS/MS analysis, we evaluated the degradation patterns of 29 antimicrobials and coccidiostats under controlled conditions, while simultaneously monitoring key parameters including temperature kinetics, pH fluctuations, short-chain volatile fatty acids (SCVFA), and nutritional content. Our findings revealed that stacking treatment demonstrated superior degradation efficiency for most compounds, achieving > 95% degradation for key antimicrobials and 54.9–74.7% for commonly used coccidiostats. Notably, the stacking method maintained optimal crude protein levels (32–34.8%) while reducing moisture content by 29.5–34.6%. Temperature profiles showed distinct patterns: aerobic treatment reached 60 °C within 24 h, while stacking achieved 50 °C over 2 weeks, both significantly outperforming anaerobic treatment (38 °C). This research provides the first comparative evidence for selecting cost-effective BL treatment methods, offering practical guidelines for agricultural operations to minimize pharmaceutical residues while preserving nutritional value for ruminant feed.

The online version contains supplementary material available at 10.1007/s11356-025-36535-9.