Microbial Counts in Forages for Horses—Effect of Storage Time and of Water Soaking Before Feeding

• Soaking forages in water for 24 hours increased counts of yeast and enterobacteria.
• Silage and haylage contained lower mold counts than hay before and after soaking.
• Increased storage time resulted in decreased mold counts in hay.
• Further studies need to address more specific analytical methods especially for enterobacteria.

Soaking of hay in water before feeding has become common practice in equine feeding to reduce number of respirable particles or content of nonstructural carbohydrates. It is, however, not known if soaking may increase general microbial load in different forages. A study was therefore performed where microbial composition of silage, haylage, and hay was analyzed before and after soaking in water for 24 hours. As storage time may also influence microbial composition of forages, the soaking procedure was evaluated after two different storage periods. Results showed that soaking increased counts of yeasts, enterobacteria, and lactic acid bacteria (LAB) and decreased mold counts. Although mold counts in hay decreased with soaking (from log 4.7 to log 3.6 colony-forming units [CFUs]/g), soaked hay still contained greater (P < .001) numbers of molds compared with silage and haylage presoaking. Counts of enterobacteria increased (P < .001) with soaking in silage (from log 1.1 to 2.7 CFU/g) and haylage (from 1.7 to 4.8 CFU/g) but not in hay (log 4.9 and 5.1 CFU/g before and after soaking). Count of yeast and LAB generally increased by soaking (P ≤ .004). Soaking forage for 24 hours may therefore reduce the hygienic quality of forage. Increased storage time (from 3 to 12 months) resulted in decreased counts of molds in hay (from log 4.8 to 3.5 CFU/g; P < .001) and decreased counts of LAB in silage (from log 8.1 to 6.6 CFU/g; P < .001) as well as in haylage (from log 6.9 to log 4.8 CFU/g; P < .001).