Mycotoxins and horses – Help is at hand

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Mycotoxins and horses – Help is at hand!
What to know and what to do….

Mycotoxins…what are they?

• Mycotoxins are harmful molecules produced by moulds (fungi) that can have a profound negative impact on horse health.
• In contrast to moulds, which are living organisms, mycotoxins are stable chemical compounds that are very difficult to destroy.
• Moulds produce mycotoxins when they are ‘stressed.’
• For example, drought, flood, frost, unusual climate changes, moisture content, temperature, and physical damage are all ‘stressors’ and can result in mould-producing mycotoxins.
• This means that mycotoxins can be produced on the crop in the field, during feed production and storage.
• Whilst it is a good idea to know about and understand the risks associated with mycotoxins, it is also important to remember that they are naturally occurring and very common.
• Animals and humans are exposed to them on a daily basis.
• There are over 500 different known mycotoxins, and it is common to find multiple mycotoxins occurring together.
• The most common moulds responsible for producing mycotoxins are:
– Aspergillus
– Fusarium
– Penicillium

Aspergillus mycotoxin	Fusarium mycotoxin	Penicillium mycotoxin
Aflatoxin	Deoxynivalenol (DON)	Ochratoxin
Ochratoxin	Zearalenone (ZEA)	PR toxin
Sterigmatocystin	T-2 toxin	Patulin
Fumitremorgens	Fumonisin	Penicillic acid
Fumigaclavines	Moniliformin	Citrinin
Fumitoxins	Nivalenol	Penitrem
Gliotoxin	Fusaric acid	Cyclopiazonic acid

The table above shows some common mycotoxins and the moulds that produce them and highlights the variety of mycotoxins produced. Also, the same mycotoxin can be produced by more than one type of mould. Fusarium moulds and their mycotoxins occur ‘in the field’, while Aspergillus and Penicillium moulds and their mycotoxins occur during storage.

Mycotoxins….what’s all the fuss?

• Horses appear more sensitive to a range of mycotoxins compared with other animals, such as cows.
• As mycotoxins are very stable, even the acidity of the stomach does little to reduce their effects.
• As they pass through the digestive system, they can affect the lining of the gut and/or be absorbed into the horse’s body, causing symptoms ranging from dermatitis to infertility to death.

Table – Main mycotoxins, their sources and pathological effects.

Mycotoxin	Source	Effects
Aflatoxin	Maize, rice, sorghum, cottonseed	Liver damage, carcinogenic, weight loss, anorexia, death
DON, T-2 toxin	Maize, wheat, barley, oat, rye	Skin lesions/disorders, immunosuppression, cystic ovaries, lethargy, anorexia
Zearalenone	Maize, hay, mixed feed	Oestrogenic, wasting of testes and ovaries, prolapse, abortion
Fumonisins	Maize, wheat	Nervous disorders, lesions on the gut and liver, immunosuppression, leukoencephalomalacia, reduced appetite, ill-thrift
Ochratoxin	Wheat, barley, oats, maize, rye	Diarrhoea, kidney and liver toxicity, foetal abnormalities, carcinogenic, retarded growth
Patulin	Straw, hay	Carcinogenic, paralysis, convulsions

Mycotoxins….what have they got to do with my horse?

Mycotoxins are everywhere!
• They may be present in feed and forage, including grazed grass, no matter how clean and mould-free it looks.
• And it’s not simply feed and forage that can be contaminated. Bedding that originates from a plant crop, such as straw, also poses a risk.
• The presence of moulds does not necessarily indicate the presence of mycotoxins but it does increase the risk. Equally, and perhaps more important to remember, there can be significant mycotoxin contamination with no visible mould.

What’s the worst that could happen?

The most common effects are poor appetite, weight loss, lethargy and skin lesions, however, in rare but severe cases, horses can succumb to Equine Leukoencephalomalacia induced by Fumonisins.

But my feed looks fine….

Mycotoxins are very stable compounds and can remain in the environment or feed for long after the mould has gone
• Therefore, just because there is no visible mould, it does not mean there are no mycotoxins.
• Also, the presence of mycotoxins will reduce the nutritional value of feed.
• Cereals (hard or concentrated feed) are most likely to be contaminated with Fusarium or Aspergillus mycotoxins.
• Generally, more than one mycotoxin will be present and ill effects are normally as a result of consuming a variety of mycotoxins.

Aspergillus mycotoxins in cereals:
• Aflatoxin – More common in warm and humid environments, it targets the liver. However, the mould itself can also cause problems via inhalation. Equine Asthma (previously known as Recurrent Airway Obstruction, RAO), has been linked to Aspergillus.
• Ochratoxin – Attacks both the liver and developing embryos.

There are two types of Fusarium mycotoxins in cereals

1. Trichothecenes – Trichothecenes (inc. DON, T-2 toxin) affect the horse’s appetite. One of the first signs of contamination with trichothecenes is feed refusal. Lethargy and loss of coordination can also be seen. Interestingly, garlic powder is often a source of trichothecenes, causing skin problems.
2. Non-trichothecenes – Non-trichothecenes include ZEA, which acts like the hormone oestrogen and can cause enlargement of the uterus, vaginal prolapse and abortion. Fumonisins are also non-trichothecenes and can result in liver and kidney damage and impaired immune function (immunosuppression). These are also responsible for Equine Leukoencephalomalacia (ELEM)

But you always get the odd mouldy bale….

This is a common statement uttered on a regular basis in every yard!
In fact, just because hay/haylage or straw is mouldy doesn’t necessarily mean it is contaminated with mycotoxins, but the chance is significantly increased.
That aside, there are numerous mycotoxins that can be found in significant quantities in forage, grazing and bedding.
The Penicillium mycotoxins, particularly Patulin, are often detected in the hay, haylage/silage and straw. Patulin is carcinogenic and can cause paralysis and convulsions. The Fusarium mycotoxin, ZEA, can also be found in forage and its effects in feed have already been outlined.

Stachybotrys charatum is a fungus found in the soil responsible for producing Satratoxins and a condition called Stachybotryotoxicosis, where horses will show signs of depression, problems swallowing and colic. Black moulds may be seen on hay and straw.

But my horse will be safe out grazing….

Mycotoxins exist on pasture too.
Fescue Toxicosis is a condition characterised by weight loss, a rough coat, elevated temperature and reproductive problems. Caused by horses grazing tall fescue contaminated with ergot alkaloids produced by the endophytic mould species Neotyphodium coenophialum, it has a higher incidence in the US than in Europe.

An endophytic species, Neotyphodium lolii, is often responsible for the condition known as ‘ryegrass staggers’. Horses exhibit poor muscle coordination, head shaking and collapse. A group of mycotoxins termed tremorgens (in particular, Lolitrem B), is implicated in this condition and is found in the lower parts of the leaf blade; hence, ryegrass intoxication is more common in over-grazed (horse-sick) pastures. However, Lolitrem B can also be found in hay. The effects of ryegrass staggers can be fully reversed if diagnosed correctly.

Additionally, ergotism is a condition associated with ergotamine, which is an ergot alkaloid produced by the parasitic mould, Claviceps purpura, that can be found in grass and cereals. While rare for the most part, ergotism can cause issues with circulation, regulation of temperature, reproductive failure and the nervous system.

The fungus Rhizoctonia leguminicola inhabits certain leguminous plants, notably red clover, and will produce the mycotoxin Slaframine when conditions are right. Consumption of sufficient levels of Slaframine leads to ‘Slobbers’ or ‘Red clover disease’ characterised by profuse salivation (slobbering).

But surely it’s up to the feed producer…

Feed mills and producers have a responsibility to ensure the feed you buy is free from contamination and fit for consumption by the animal.
Cereals commonly used in feed manufacture are routinely tested for certain mycotoxins, usually DON and ZEA and, if levels are sufficient, the sample or batch is rejected.
Respectable feed manufacturers will also follow procedures with regard to processing, packaging and storage to minimise the risk/level of contamination. Many of them will have developed their own audit to analyse and assess possible threats from a mycotoxin challenge. These audits can also be adapted by the horse owner to evaluate and minimise the threat from mycotoxins.

Ok, so how do I help protect my horse?

Mould and mycotoxin contamination of plants before harvest are unavoidable, but the threat can be reduced by controlling the storage and feeding of forage, cereals and bedding.

What is HACCP, and how is it relevant to me?

HACCP has been around for a long time and is used extensively in many industries to identify potential hazards and minimise their risks from them. It was initially developed as a microbiological safety system in the early days of the US space programme in order to produce safe food for astronauts.

It can be used as a logical, systematic basis to identify and minimise the risks associated with mycotoxin challenges on the yard.

The basics of HACCP

1. Conduct a hazard analysis – e.g. Look at all the potential areas that might contribute to a mycotoxin challenge.
2. Determine the Critical Control Points (CCPs) – e.g. Decide which areas could eliminate or reduce possible contamination.
3. Establish critical limits – e.g. Decide on thresholds for the CCPs above which there would be a mycotoxin problem.
4. Establish a monitoring system – e.g. Create a chart or checklist.
5. Establish a procedure for corrective action when monitoring indicates a deviation from an established critical limit – e.g. Have a plan of action for when a risk area goes above the thresholds you set.
6. Establish verification procedures to confirm the HACCP plan works – e.g. Have another checklist of action list that allows you to check whether your action plan works.
7. Establish documentation concerning all procedures and records regarding these steps and their application. i.e. Write everything down!

What areas should I think about?

Feed
– Forage – hay/haylage
– Grazing
– Concentrate/hard feed
– Straights
– Storage
– Use

Water
– Contamination

Equipment
–  Feed bins/containers
–  Feed buckets
–  Water buckets
–  Any equipment used to mix feed
–  Fixtures and fittings

Environment
– Stables and pasture – surfaces
– Bedding

Animals
– Signs and symptoms
– Refusal of feed
– Blood tests/liver biopsies

What simple steps can I take?

Feed

• Check bagged feed for moulds and moisture content – ideally should be around 10% moisture (90% dry matter)
• Check conserved and fresh forage for moulds and mycotoxins
• Check bedding material for moulds and mycotoxins – including straw, shavings etc
• All feed offered should be fresh
• Store feed in dry, cool conditions
• Use haylage within 2-3 days of opening
• Check the temperature of hay and haylage – very hot hay or haylage is indicative of aerobic spoilage.
• Avoid soaking hay for prolonged periods – unless soaking to significantly reduce the sugar content, only soak for ~30 minutes. Soak for less time in hot weather.
• Test forage and/or feed for the presence of mycotoxins using a ???
• Test forage and/or feed for the presence of mycotoxins using a broad spectrum lab-based mycotoxin analysis, such as Alltech’s 37+ test.
• Include a proven mycotoxin binder in the horse’s feed.

Water

–  Clean water buckets/troughs/utensils regularly

–  Check for signs of mould etc, and remove

–  Check for contamination of non-mycotoxin contaminants e.g. heavy metals

Animals

–  Check for odd, unexplained signs and symptoms

–  Keep a record of any skin lesions, swollen joints, infertility, persistent lethargy and poor appetite. The symptoms of mycotoxicosis are often very vague and can resemble other conditions.

–  It might be advisable in some cases to have blood tests taken, including liver function tests.

What simple steps can I take?

Equipment

–  Clean and wash out feed bins between batches – endure they are dry before the new batch is put in

–  Clean feed buckets after use and ensure they dry before being stored

–  Store feed in a dry, well-ventilated area – aerate bins

–  Keep all additional feeding equipment (grain rollers/crushers) clean

–  Risk of rodents/pests

Environment

–  Check the ventilation in stables and barns – cobwebs are a good indicator that there is no air movement in that area

–  Check moisture levels in stables and barns

–  Check for the presence of moulds, particularly with wooden structures

–  Disinfect stables, barns, tack rooms and feed rooms regularly

–  Avoid over-grazing pastures

–  Monitor the level of red clover or other legumes present in pasture and take note of any unusual weather conditions during the pasture growing season.

What sort of things can I measure?

• Visual checking of feed and forage:
  – Storage
  – Feeding practices – handling
• Moisture levels
• Ventilation
  – Look for cobwebs

• Temperature
  – Conserved forage (hay/haylage)
  – Grains/hard feed
  – Ambient
• Moulds
  – Visual identification, including colour
  – Send a sample for a mould count
• Mycotoxin analysis
  – This is quite an expensive analysis, and only certain mycotoxins can currently be tested commercially
• Any health problems of both horse and human

Creating a checklist or flow chart that is kept on the yard and that everyone understands is an excellent way to help reduce the risk of a potential mycotoxin problem.

The DDM Team are working with Alltech (UK) Ltd to test, trial and use their Alltech (UK) Ltd 37+ mycotoxin analysis programme. We will have a few Members whose horse’s are at risk of mycotoxins take the test and share the analysis.