Toxins and toxin pressure
What are they?
At a glance
Toxins in feed and pasture, including mycotoxins from mouldy silage or stored feeds and plant or grass toxins in pasture, reduce feed intake, damage liver function and impair fertility and milk production. They can also cause neurological signs such as tremors, stagger and recumbency. Look for clusters of affected cows rather than isolated cases.
Managing toxin risk is about prevention, early detection and rapid removal of suspect feeds. Minerals and supportive nutrition help cows cope, but clearing contaminated feeds and reducing exposure are the priority.
Need more help? talk with your Agvance consultant.
Symptoms
- Tremors, stiff legs, staggering
- Reduced feed intake
- Fatigue, not wanting to stand
- Poor body condition
- Drowsiness or unresponsiveness
- Swollen legs
- Slips / Abortions
What you might notice on-farm
Clinical signs vary with the toxin and exposure level. Common observations include:
- Tremors, stiff legs, stumbling or staggering
- Reduced feed intake and rapid drop in milk yield
- Lethargy, reluctance to stand and poor body condition over weeks
- Drowsiness, unresponsiveness or collapse in severe cases
- Swollen legs or photosensitisation with some plant toxins
- Reproductive issues such as slips, abortions or failure to cycle
- Herd-level patterns where multiple cows on the same feed or paddock are affected
If signs are sudden and clustered, suspect a feed or pasture source. Check recently fed supplements, silage face, bale quality and any unusual items fed to stock.
Ergot toxins can cause havoc on farm. Here’s what to watch for.
What good looks like
- No clusters of neurological signs, steady milk production and normal feed intake across the herd
- Clean, well-made silage and stored feeds with no visible mould, heat damage or rot
- Pastures monitored for toxic species and grazed or managed to avoid high-risk periods
- A documented feed and silage testing routine for high-risk feeds and prompt removal of suspect batches
Follow these quick checklists
What to do today
- Inspect all recently fed feeds, including silage faces, bales, maize, grain stores, and supplement tubs for visible mould, odd smells or heating. Remove any suspect feed immediately.
- Check which cows were fed each ration or grazed each paddock, and list affected animals. Cluster mapping helps pinpoint the source.
- Stop feeding any novel or questionable feeds such as spoiled vegetable waste, lollies or bakery waste.
What to do this week
- Sample suspect feeds for laboratory mycotoxin testing, prioritise the feeds most recently introduced or fed to affected cows.
- Isolate and monitor affected cows, record signs, milk loss and any recent changes in feed or pasture.
- Talk to your feed supplier or contractor about storage, harvesting and handling that could reduce contamination risk.
During the season:
- Keep close attention to fresh cows and any changes in feed or supplement regimes. Fresh cows are vulnerable because they often receive different feed mixes and supplements.
- If toxin exposure is confirmed or strongly suspected, work with your vet and adviser to remove the source, support affected cows nutritionally and consider toxin binders where appropriate and evidence supports their use for the specific toxin.
Issues, likely causes and where to start
Treat toxin problems as a feed system issue, the likely cause is often obvious once you map which cows were exposed.
If multiple cows show neurological signs or tremors
Likely causes:
- Grass staggers from magnesium-deficient pastures or sudden changes in pasture chemistry after rain or frost
- Acute mycotoxin exposure from mouldy silage, spoiled maize or damp baleage
- Ingestion of toxic plants or agricultural waste in a paddock or feed pad
Start with:
- Remove access to the suspect pasture or feed immediately. Provide clean feed and water.
- Check recent weather events, grazing rotation and any unusual feed inputs.
- Contact your vet for clinical assessment and arrange feed testing.
If reduced intake and gradual loss of condition across a group
Likely causes:
- Chronic mycotoxin exposure in silage, hay or stored grain lowering appetite and liver function
- Low palatability due to heating or mould contamination causing selective intake and weight loss
Start with:
- Stop feeding suspect batches, replace with clean feed and observe recovery.
- Test suspect feeds for mycotoxins and discuss results with your adviser.
- Support cows with palatable, easily digestible feed and ensure water access is unrestricted.
If reproductive losses or fertility problems appear
Likely causes:
- Mycotoxins such as zearalenone affecting cycling and conception
- Chronic liver load from multiple low-level toxins reducing fertility and immunity
Start with:
- Investigate feed history across mating and early gestation periods and test suspect feeds.
- Review trace mineral and vitamin status with your adviser as deficiencies can worsen reproductive responses.
- Work with your vet on reproductive monitoring and culling or segregation strategies for affected stock.
When to call the vet
Call your vet straight away if:
- You have sudden neurological signs, collapses or several cows down in a short period of time
- You have unexplained abortions, multiple cows slipping or a rapid herd-level drop in milk production
- You need clinical diagnosis, treatment, toxicology advice or assistance with sampling and testing
Early veterinary involvement helps with rapid diagnosis and can accelerate the removal of the toxin source and the treatment of affected cows.
How minerals fit in
Minerals cannot cure toxin exposure, but correct mineral and nutritional status improves resilience and recovery.
How minerals help
- Healthy liver function requires adequate trace minerals and vitamins. Selenium, copper and zinc are important for detoxification enzymes and immune response.
- Magnesium and calcium support neuromuscular function and can reduce symptoms where grass chemistry creates transient deficiencies.
- Keeping cows in correct condition and with consistent energy intake reduces the impact of low-level toxin exposure.
Practical mineral checks
- Review whether close-up and fresh cow rations dilute or alter mineral intake. Crops and supplements can change mineral balance quickly.
- Ensure delivery methods reach shy feeders and high-risk cows. Free-choice minerals work if monitored for intake, but in-shed or in-mix delivery is more reliable.
- If mycotoxins are confirmed, discuss with your adviser whether specific support or binders are appropriate and which minerals to prioritise during recovery.
FAQs
How quickly will cows recover after removing contaminated feed?
Recovery timing depends on the toxin and exposure level. Some cows respond within days to clean feed and supportive care; chronic or high-dose exposures can take weeks or longer and may cause lasting damage.
Can mycotoxin binders fix the problem?
Binders can reduce absorption for some mycotoxins, but are not a substitute for removing contaminated feed. Use binders only on veterinary or adviser recommendation based on identified toxins.
Should I test all my silage and baleage?
Test high-risk batches first, such as those with visible mould, heat damage or poor fermentation. For peace of mind, include samples from any new silage, maize or baleage you plan to feed to fresh cows.
What pasture signs suggest a risk of grass toxins?
Rapid change in plant composition after drought, frost or rain, grazing brassica-heavy paddocks or pastures with suspect native species can increase toxin risk. Photosensitisation in stock or neurological signs in sheep can be early warnings.
Can feeding extra minerals prevent toxin problems?
No. Good mineral status supports resilience but will not prevent poisoning from contaminated feed. The priority is identifying and removing the toxic source, then supporting affected cows nutritionally.
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