Ergot is a fungal disease caused by Claviceps purpurea that can infect cereals and grasses. In order of decreasing susceptibility, the disease affects rye, triticale, wheat, barley and rarely oats. It is understood that ergot is more prevalent in years following cool, wet conditions during flowering, with spring varieties being more susceptible, although there does not seem to be significant varietal differences. Grass weeds, particularly black grass, are also susceptible.
Initial infection is via airborne spores arising from the “explosion” of the ergot bodies that have been lying dormant in the soil over winter. A sticky exudate, known as “honeydew”, forms on the ear of the crop and contains numerous spores that are then spread onto uninfected ears by physical contact and insects. The spores access the seed head and replace some of the seeds as they develop and form into sclerotia (ergot bodies), which protrude from the ear, appearing as small purplish-black horn like structures. These ergot bodies are either harvested with grain or fall to the ground where they remain dormant for the following year.
Ergot bodies contain numerous chemical compounds, including potent toxins, known as alkaloids. The most potent of these are ergotamine, ergotsine, ergonovine, ergocristine, ergocryptine, and ergocornine. Ingestion of these alkaloids can cause ergotism and, although the disease has little effect on the yield of the crop, ingestion can pose a risk to both human and animal health. It should be noted however that transfer from feed to food of animal origin is negligible.
They can act on the central nervous system and interfere with nerve activity; they are also known to cause constriction of peripheral blood capillaries leading to oxygen starvation and gangrene of the limbs. Symptoms can be worse in extreme temperatures.
Acute ergot poisoning arising from the ingestion of large quantities of ergot in a short space of time can result in paralysis of the limbs and tongue, digestive upsets and abortion.
In mammals two forms of ergotism have been reported:
Early signs of ergot poisoning are likely to be unpalatability of feed, leading to reduced feed intake and impaired performance. The main symptoms that have been observed in farm animals are as follows:
It is hard to predict the adverse effects of ergot contaminated feed due to sclerotia being variable in alkaloid content and therefore tolerance to individual ergot alkaloids present in feed materials is inconsistent.
Poultry appear to be able to tolerate higher levels of ergot compared to some other livestock, such as pigs, but it’s generally agreed in the literature that safe dietary levels of ergot sclerotia for chickens is in the range of 0.3%-0.8% by weight. However, this will depend on the ergot alkaloid concentrations.
An EFSA report published earlier this year (January 2024) suggests the reference points for adverse health conditions for ergot alkaloids are 2.1mg/kg for chickens for fattening, 3.7mg/kg for hens and 0.2mg/kg for ducks. This agrees with other trials that suggest layers may be able to tolerate higher levels of ergot compared to broiler chicks. The variability in results could suggest that long-term exposure to ergot alkaloids results in an adaptive response.
Within the last couple of years, the EU has revised limits for ergot sclerotia and alkaloids although this is not GB-retained law. GB law for animal feed has no legal limitations on alkaloids, purely a maximum limit for rye sclerotia of 1g/kg.
EU law states ergot sclerotia maximum level is 0.2g/kg in unprocessed cereals except for maize, rye and rice. Currently the limit for unprocessed rye is 0.5g/kg, although there are plans to reduce this further to 0.2g/kg in 2025 in the EU. Similar to GB, EU has no alkaloid limitations for animal feed grains. Ergot alkaloids maximum levels for cereals and their products for food as follows:
The AIC Contract for Grains and Pulses No.2/16 states: “grain shall not contain more than 0.001% ergot by weight for feed grain and zero tolerance for all other grain.”
Elsewhere in the world, limits for ergot alkaloids in animal feeds have been set for some time. In Canada maximum levels of ergot alkaloids have been established: 6 mg/kg in pig feed, 3 mg/kg in cattle, sheep, horses and 9 mg/kg in chicks. Guidance in Uruguay states that ergot alkaloids should not be detectable in feed for pigs with a guidance level of 0.45 mg/kg in other feed.
Since 2016, AHDB has funded a project monitoring contaminants, including ergot, in UK cereals. The project includes analysis of wheat, barley, oats and co-milling products. Results from the 2023 harvest show the highest level of total alkaloids detected in UK feed wheat was 1.339 mg/kg with the mean levels higher in all products (except malting barley) in 2023 compared to 2022. The full report can be found here.
Visual inspection is a quick and practical way of determining risk, even though the absence of physical sclerotia does not confirm ergot alkaloids are not present. The image below shows the presence of the characteristic black banana shaped bodies in a sample of wheat. Typically they are 8-15mm long and 3-5mm thick.
While there seems to be conflicting information about the “safe” level of ergot for animal feed, from a practical perspective and to cover varying species tolerances, loads should be rejected if ergot bodies are present in a sample of grain.
Where rejection of loads may not be practical, eg home-grown cereals for own use, there are options to reduce risk. Please get in touch with a Premier Nutrition nutritionist to discuss further.