🩺 Prevent Moldy Hay Risks in 2025: A Vet’s Guide by Dr Duncan Houston BVSc

Meta description: Moldy hay can harbor spores, mycotoxins, and botulinum—leading to heaves, colic & liver disease. Learn inspection, storage, prevention, remediation, and Ask A Vet support strategies.

1. 🌾 Why Moldy Hay Is a Threat

Mold and fungi thrive in damp hay that didn’t dry properly pre-baling, became moist in storage, or sat on the ground. Because horses are hindgut fermenters and highly sensitive to airborne particles and toxins, feeding moldy or dusty hay can trigger:

• Respiratory disease (heaves/RAO): due to inhaled spores and endotoxins :contentReference[oaicite:3]{index=3}
• Colic and diarrhea: from GI irritation and bacterial imbalances :contentReference[oaicite:4]{index=4}
• Mycotoxin exposure: liver damage, immune suppression, feed refusal :contentReference[oaicite:5]{index=5}
• Botulism risk: spores from Clostridium in rotting hay :contentReference[oaicite:6]{index=6}

2. 🔍 Signs Your Horse May Be Exposed

• Coughing, nasal discharge, wheezing, or exercise intolerance :contentReference[oaicite:7]{index=7}
• Colic signs—pawing, restlessness, abdominal pain :contentReference[oaicite:8]{index=8}
• Diarrhea, loose manure, decreased appetite or weight loss :contentReference[oaicite:9]{index=9}
• Lethargy, poor coat, unexplained illnesses or immune weakness :contentReference[oaicite:10]{index=10}

3. 🏠 Storage Best Practices to Avoid Mold

Proactive storage can prevent mold formation:

• Elevate hay bales: Use pallets or racks so airflow circulates underneath :contentReference[oaicite:11]{index=11}
• Dry conditions: Bale below 20% moisture; ventilate storage :contentReference[oaicite:12]{index=12}
• Monitor moisture & temperature: Probe-stack temps >130°F risk spontaneous combustion :contentReference[oaicite:13]{index=13}
• Check humidity: Use dehumidifiers or airflow fans in damp regions :contentReference[oaicite:14]{index=14}
• Stack smart: Avoid ground contact, protect from rain, leave space for ventilation :contentReference[oaicite:15]{index=15}

4. 👃 Inspect Before Feeding

• Visual cues: Look for white, green, or black mold spots, dusty cobweb-like spores :contentReference[oaicite:16]{index=16}
• Smell test: Musty, “moldy” barny odor means discard :contentReference[oaicite:17]{index=17}
• Check edges and bales bottom: Moisture collects there—inspect these areas :contentReference[oaicite:18]{index=18}
• Feed trial: Offer a small flake; if rejected or triggers cough, don’t feed :contentReference[oaicite:19]{index=19}

5. 🗑️ What to Do with Moldy Bales

• Discard dangerous bales: Burn, compost far away, or repurpose for non-sensitive livestock :contentReference[oaicite:20]{index=20}
• Soak mildly dusty hay: Wet for 5–30 min to reduce airborne spores :contentReference[oaicite:21]{index=21}
• Steam questionable hay: DIY steam treatment kills spores and improves smell :contentReference[oaicite:22]{index=22}
• Test hay for toxins: Use diagnostic labs for suspect hay :contentReference[oaicite:23]{index=23}

6. 🩺 Treating Affected Horses

Consult your veterinarian if your horse shows signs:

• Treat respiratory issues: corticosteroids, bronchodilators, improve backlog airflow :contentReference[oaicite:24]{index=24}
• Manage colic or diarrhea: fluids, GI protectants, supportive nutrition :contentReference[oaicite:25]{index=25}
• Address mycotoxin exposure: liver-supportive supplements, enzymes, probiotics :contentReference[oaicite:26]{index=26}
• Botulism suspicion: prompt antitoxin therapy and intensive care :contentReference[oaicite:27]{index=27}

7. 🛡️ Preventive Measures Year-Round

• Rotate hay stocks; use FIFO principle :contentReference[oaicite:28]{index=28}
• Clean hay storage regularly; remove old debris :contentReference[oaicite:29]{index=29}
• Test humidity/temperature seasonally :contentReference[oaicite:30]{index=30}
• Feed outside when dusty, avoid barn dust buildup :contentReference[oaicite:31]{index=31}
• Use quality hay from reputable harvesters :contentReference[oaicite:32]{index=32}

8. 🤝 Ask A Vet Feed & Health Support

• 📋 Remote hay-audits: owners upload photos/videos; vet advises feed decisions
• 📆 Storage schedules & reminders for moisture checks, stock turnover
• 📊 Tool tracking storage conditions, mold risk alerts, test results
• 📚 Webinars: “Hay Quality,” “Moisture Monitoring,” “DIY Hay Steaming”
• 🔁 Follow-up prompts for veterinary checks if horses show signs

9. ❓ FAQs

Is small mold safe if I soak hay?

Soaking removes spores but not mycotoxins; only use marginal hay sparingly, prefer feeding outdoors with clean alternatives first.

Can I still give hay with just surface mold?

Only if interior is clean—and you remove external dust, soak or steam before feeding. If respiratory signs ensue, stop immediately.

How often check hay temperature?

Probe during stacking and monthly in storage; >130 °F requires immediate action to cool and ventilate.

Is moldy hay dangerous even if not eaten?

Yes—dust inhalation alone can exacerbate heaves or allergies. Keep feeding area ventilated or feed outside.

10. ✅ Final Takeaway

Feed quality begins in the field, continues through clean storage and vigilant inspection. Proper handling keeps hay nutritious and safe—while Ask A Vet helps with monitoring, storage planning, and tailored health checks to protect your horse’s respiratory, digestive, and immune health. As Dr Duncan Houston, I’m here to help you build mold-prevention habits that keep your horse thriving into 2025 and beyond. 🌟