Mapping the bacterial ecology on the phyllosphere of dry and post soaked grass hay for horses.
Authors: Moore-Colyer Meriel, Longland Annette, Harris Patricia, Zeef Leo, Crosthwaite Susan
Journal: PloS one
Summary
# Editorial Summary Hay soaking is widely advocated to reduce dust and sugar content for horses with respiratory or metabolic sensitivities, yet the practice's effect on microbial populations remains poorly characterised. Moore-Colyer and colleagues analysed bacterial communities on perennial ryegrass and two meadow hay types using 16S rRNA gene sequencing, comparing untreated hay with material soaked for 1.5, 9 or 16 hours. Whilst water-soluble carbohydrate reduction was dose-dependent (18–42% loss over 16 hours), bacterial load and community composition changed unpredictably independent of sugar leaching, with notable shifts in bacterial family profiles emerging post-soaking, particularly in meadow hays. The findings suggest that hay type substantially influences how microbial ecology responds to soaking, raising concerns that the practice may inadvertently introduce unfamiliar bacterial taxa into the equine digestive tract without offering predictable hygiene benefits. Practitioners should recognise that soaking protocols lack standardisation in their microbiological outcomes and consider whether alternative dust-reduction strategies might be equally effective without introducing this biological variability.
Read the full abstract on PubMed
Practical Takeaways
- •Soaking hay provides inconsistent WSC reduction and unpredictably alters bacterial profiles—results vary by hay type and soak duration, so monitor individual batches rather than relying on standardized protocols.
- •The bacterial load and composition changes during soaking may introduce unfamiliar microorganisms to the equine gastrointestinal tract, potentially compromising digestive health; consider alternative dust-reduction methods (steaming, pelleting) if soaking is used for metabolic horses.
- •Hay type matters significantly—meadow hays and ryegrass hays respond differently to soaking, so adjust feeding protocols based on your specific forage source rather than applying one standard soak time.
Key Findings
- •Soaking hay for 1.5, 9, and 16 hours reduced WSC by 18%, 38%, and 42% respectively, but with high variability (±10.7 to ±43.7 g/kg).
- •No significant relationship existed between WSC leaching and bacterial growth or profile changes during soaking.
- •Grass type (perennial ryegrass vs. meadow hay) significantly influenced bacterial profiles and their responses to soaking, with clustering differences evident post-soaking.
- •Soaking caused unpredictable alterations in bacterial family profiles and inconsistent growth in total aerobic bacteria loads, potentially decreasing hay hygiene quality.