Identifying and Preventing Toxic Hay Contamination
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Why Winter Brings Unique Hay-Related Poisoning Risks
Winter feeding programs rely heavily on stored hay, creating opportunities for toxic plant exposure that differ significantly from grazing-season risks. When cattle consume hay, they cannot selectively avoid toxic plants as they might when grazing. Contaminated bales deliver concentrated doses of toxins, and multiple animals often share exposure from a single source. Understanding hay contamination risks is essential for winter livestock safety.
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Types of Hay Contamination
1. Toxic Plant Contamination
|-------|-------|-----------------|------------| | Perilla mint | Perilla ketones | Fully retained | Extreme | | Cocklebur (mature) | Carboxyatractyloside | Partially retained | High | | Jimsonweed | Tropane alkaloids | Fully retained | High | | Oleander | Cardiac glycosides | Fully retained | Extreme | | White snakeroot | Tremetol | Fully retained | High | | Rayless goldenrod | Tremetol | Fully retained | High | | Nightshade species | Solanine | Partially retained | Moderate-High | | Buttercup | Ranunculin | Reduced (unstable) | Low-Moderate | | Water hemlock | Cicutoxin | Partially retained | High |
|-------|-------|--------------|-------| | Wild cherry | Cyanogenic glycosides | Reduced when dry | Wilted leaves still dangerous | | Sorghum/sudan | Prussic acid | Reduced when cured | Test if cut after frost | | Buttercups | Ranunculin | Usually safe | Volatile compound dissipates | | Bracken fern | Ptaquiloside | Reduced | Still problematic if high concentration |
2. Nitrate Contamination
- Hay retains same nitrate level as when cut
- Nitrate-contaminated hay remains dangerous indefinitely
- No visual indicator of nitrate content
- Hay cut after fertilizer application
- Hay from weedy fields (pigweed, lambsquarters)
- Hay from fields with feedlot runoff
- Sorghum-sudan hay (inherent nitrate accumulator)
- Johnsongrass hay
- Oat hay cut during drought
3. Mycotoxin Contamination
- Hay baled at >18% moisture for large rounds
- Wet storage conditions
- Ground contact (bottom of stack)
- Rain damage to stacks
- Produced by Aspergillus species
- Primarily in corn and grain-contaminated hay
- Causes liver damage, immune suppression
- Can pass through milk
- Corn stalk contamination
- Liver and kidney damage
- Equine leukoencephalomalacia (horses)
- Estrogenic effects
- Reproductive problems, especially in heifers
- Causes vulvar swelling, irregular cycles
- Affects fescue and other grasses
- Causes vasoconstriction, gangrene (fescue foot)
- Summer slump syndrome
- Reproductive issues
- "Slobber factor"
- Excessive salivation
- Generally not life-threatening
4. Foreign Object Contamination
- Wire fragments
- Dead animals (botulism risk)
- Plastic bags/film
- Metal debris from equipment
- Battery casings
- Clostridium botulinum produces potent neurotoxin
- Even small carcass can produce lethal toxin amount
- Silage at greater risk than dry hay
- Clinical signs: progressive paralysis, death
Hay Testing and Inspection
Visual Inspection Protocol
- Green color indicates good quality, proper curing
- Yellow/brown may indicate rain damage or late cutting
- Gray/black patches indicate mold
- Bleached white indicates weathering
- Smell Assessment:
- Fresh, clean smell = good quality
- Musty smell = mold contamination
- Burnt/caramel smell = heat damage during storage
- Ammonia smell = excess moisture, spoilage
- Texture Assessment:
- Soft, pliable stems = properly cured
- Brittle, shattering = over-cured or sun damaged
- Slimy or matted = moisture/mold damage
- Dusty = mold spores present
- Physical Contamination Check:
- Look for foreign objects
- Check for weed seed heads
- Identify visible toxic plants
- Note insect damage or rodent activity
Laboratory Testing
|-----------|-------------------| | Unknown source hay | Nitrate, basic quality | | Drought-year hay | Nitrate (mandatory) | | Sorghum/sudan hay | Nitrate and prussic acid | | Suspected mold | Mycotoxin panel | | Reproductive problems in herd | Zearalenone, ergot | | Weedy hay | Nitrate, visual ID | | Premium price hay | Full quality analysis |
- SDK Laboratories (multiple locations)
- Servi-Tech Laboratories
- Dairyland Laboratories
- Local extension service recommendations
- Combine cores into clean, labeled bag
- Mix thoroughly before sending subsample
- Keep samples dry and cool
- Ship promptly to avoid degradation
- Include all relevant information on submission form
Cost-Benefit of Testing
- Full forage quality panel: $30-50
- Mycotoxin screening: $50-100
- Comprehensive analysis: $75-150
- Abortion storm: $500-1,500 per head
- Herd health issues: $50-200 per head
- Replacement costs and lost production: incalculable
Specific Winter Hay Hazards
Perilla Mint in Hay
- Often grows in shaded field edges included in hay
- Small amounts can cause fatal pulmonary damage
- No effective treatment once symptoms appear
- Difficult to identify in processed hay
- Opposite leaves with serrated edges
- Purple/green coloration may persist
- Distinctive mint-like odor when crushed
- Seed heads present in fall-cut hay
- Open-mouth breathing
- Extended head and neck
- Subcutaneous emphysema (crackles under skin)
- Reluctance to move
- Death from respiratory failure
- Reject hay from fields with known perilla
- Avoid purchasing hay from unknown sources
- Inspect all hay bales before feeding
Blister Beetle Contamination
- Beetles swarm on alfalfa during bloom
- Crushed beetles in hay retain toxicity
- Horses extremely susceptible; cattle also affected
- Lethal dose in horses: 4-6 grams of beetles (30-50 beetles)
- First cutting (highest risk)
- Crimped/conditioned hay (crushes beetles)
- South-central US (highest beetle populations)
- Hay from fields adjacent to grasshopper-prone areas (beetles eat grasshopper eggs)
- Frequent urination, straining
- Bloody urine
- Elevated temperature
- Shock, death
- Avoid first-cutting alfalfa
- Inspect hay closely before feeding
- Ask about harvesting practices (sickle bar vs. crimper)
- Consider grass hay alternatives
Fescue Toxicosis (Ergot Alkaloids)
- Alkaloid levels may actually concentrate during curing
- Pregnant cows at highest risk
- Winter stress compounds effects
- Rough hair coat, failure to shed
- Reduced weight gains
- Poor milk production
- Agalactia (no milk at calving)
- Dystocia and retained placenta
- Abortion and stillbirths
- Never feed to pregnant cows in last trimester
- Dilute with other hay sources
- Consider novel endophyte varieties for hay production
Moldy Sweet Clover Poisoning
- Mold converts coumarin to dicoumarol
- Dicoumarol is a potent anticoagulant
- Hemorrhagic disease results
- Takes weeks of consumption to cause problems
- Poorly cured sweet clover
- Large round bales with spoilage zones
- Extended feeding period (2+ weeks)
- Hematomas after injections
- Bloody feces or urine
- Sudden death from internal hemorrhage
- Stillbirths, neonatal deaths
- Avoid feeding moldy sweet clover
- Rotate with non-clover hay every 2 weeks
- Watch for minor bleeding as early warning
Safe Hay Sourcing and Storage
Purchasing Guidelines
- Were there any weeds or toxic plants in the field?
- What was the weather during cutting and curing?
- What was the moisture content at baling?
- How has the hay been stored?
- Is a forage analysis available?
- What is the cutting date?
- For alfalfa: Was it cut during bloom? What harvesting equipment was used?
- "Mixed grass hay" with no details
- Hay from unknown or changing sources
- No forage analysis available
- Abnormally low price
- Visible mold, weeds, or foreign material
- Ammonia or musty smell
Storage Best Practices
- Good air circulation
- Protected from prevailing weather
- Away from chemical storage
- Accessible for equipment
- Stack in pyramid shape for water runoff
- Leave space between rows for air circulation
- Use quality tarps secured against wind
- Inspect regularly for rodent activity
- Feed oldest hay first (first in, first out)
Winter Feeding Management to Minimize Risk
Hay Introduction Protocol
- Test if any concerns exist
- Introduce gradually over 7-10 days
- Monitor cattle closely for first 2 weeks
- Document the source and lot for records
Monitoring During Feeding
- Manure consistency and color
- Respiratory rate and effort
- Body condition trends
- Behavior changes
- Decreased hay consumption
- Diarrhea or constipation
- Increased respiratory rate
- Excessive salivation
- Abortion or reproductive issues
- Any sudden deaths
Mixing and Dilution Strategies
- Mix high-nitrate hay with low-nitrate hay
- Limit high-nitrate hay to 50% of diet or less
- Feed grain with high-nitrate hay (improves rumen adaptation)
- Introduce gradually over 5-7 days
- Never feed to pregnant animals or those with limited access to water
- Add mycotoxin binders to mineral
- Limit exposure duration
- Avoid feeding to young or pregnant animals
- Monitor for subclinical effects
Emergency Response to Hay-Related Poisoning
Immediate Actions
- Count and assess all cattle
- Isolate affected animals
- Contact veterinarian
- Preserve hay samples for testing
- Document everything
- Collect samples from multiple bales
- Note which bales cattle were consuming
- Store samples dry and away from other feed
- Label with date, lot, and location information
Treatment Considerations
- Remove from source
- Supportive care
- Prognosis good if treated early
- Supportive care
- Activated charcoal may help (acute cases)
- Long-term recovery possible with clean feed
- Many have no effective treatment
- Supportive care primary option
- Early intervention critical
Record Keeping for Hay Safety
Hay Purchase Log
``` PURCHASE DATE: ________ SUPPLIER: ________________ CONTACT: ________________
HAY DETAILS: Type: ________________ Cutting: ______ (1st, 2nd, etc.) Cutting Date: ________ Quantity: ______ bales Weight per bale: ______ lbs Price: $______ per bale/ton
QUALITY ASSESSMENT: Color: ________________ Smell: ________________ Texture: ________________ Moisture (if tested): ______% Visible contamination: ________________
LAB TESTS: [ ] Nitrate: ______ ppm [ ] Crude Protein: ______% [ ] TDN: ______% [ ] ADF: ______% [ ] NDF: ______% [ ] Mycotoxin panel: ________________
FEEDING DATES: Started: ________ Finished: ________ Animals fed: ________________
NOTES: ________________ ________________ ```
Incident Documentation
``` DATE OF INCIDENT: ________ HAY LOT INVOLVED: ________
AFFECTED ANIMALS: Number: ______ ID/Tag numbers: ________________ Age/Class: ________________
CLINICAL SIGNS OBSERVED: ________________ ________________
TIMELINE: First symptoms: ________ Hay removed: ________ Vet contacted: ________ Outcome: ________________
LABORATORY RESULTS: Hay analysis: ________________ Animal samples: ________________
DISPOSITION OF HAY: [ ] Destroyed [ ] Diluted and fed to non-susceptible animals [ ] Returned to supplier [ ] Other: ________________
FOLLOW-UP ACTIONS: ________________ ```
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Prevention Checklist for Winter Hay Feeding
Before Winter
- [ ] Assess total hay needs for winter
- [ ] Source hay from reputable suppliers
- [ ] Test all hay for nitrates (especially drought-year hay)
- [ ] Inspect all purchased hay before delivery acceptance
- [ ] Store hay properly to prevent spoilage
- [ ] Inventory and organize by lot/source
During Winter
- [ ] Feed oldest hay first
- [ ] Inspect each bale before feeding
- [ ] Monitor cattle daily during feeding
- [ ] Rotate hay sources to limit exposure to any single lot
- [ ] Watch for signs of toxicity in herd
- [ ] Maintain feeding records
If Problems Arise
- [ ] Stop feeding suspect hay immediately
- [ ] Contact veterinarian
- [ ] Collect and preserve samples
- [ ] Document all observations
- [ ] Report to extension service if widespread issue
Related Resources
- Hay Quality Testing Checklist
- Nitrate Testing Lab Directory
- Toxic Plant ID Guide
- Moldy Feed: Mycotoxin Dangers
- Emergency Vet Contact Template
Sources and References
- Ball, D.M., Hoveland, C.S., and Lacefield, G.D. "Southern Forages." 5th Edition.
- Texas A&M AgriLife Extension. "Nitrate Accumulation in Forages."
- Merck Veterinary Manual. "Mycotoxicoses" and "Nitrate and Nitrite Poisoning."
- Oklahoma State University Extension. "Prussic Acid Poisoning in Cattle."
- University of Missouri Extension. "Testing Livestock Feeds for Nitrate."
- Whitlow, L.W. "Evaluation of Mycotoxin Binders." North Carolina State University.
- Raisbeck, M.F. "Nitrate/Nitrite Toxicosis." Veterinary Clinics of North America.
- USDA-ARS. "Poisonous Plant Research Laboratory Publications."
Last Updated: January 2026
