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Ergot in Feed: Is There a Safe Concentration for Beef Cattle?
Cattle that consume feeds contaminated with the plant disease ergot can have reduced feed intake, gangrene of extremities, lameness, loss of pregnancy and heat stress. Ergot is caused by the fungus Claviceps purpurea; the alkaloids (toxins) present in the ergot bodies are toxic to cattle. Another fungi species called Fusarium graminearumcauses fusarium head blight and produces deoxynivalenol (DON), which can also be toxic to cattle. Many types of feed, including cereal crops, can become infected by ergot and contain hazardous concentrations of alkaloids, with the risk of cattle toxicity increasing if other mycotoxins like DON are present.
Ergot typically develops when wet and cool conditions occur during the flowering stages of cereals and grasses. However, ergotism in cattle has been observed in drought years as well. Grain screenings can be highly contaminated with ergot and are often an interesting alternative feed resource in a drought year.
The Canadian Food Inspection Agency recommends a concentration of ergot toxins called alkaloids to be no greater than 2.0-3.0 parts per million (ppm).1
Dr. Gabriel Ribeiro and his team at the University of Saskatchewan recently completed a study evaluating the impacts of the increasing concentrations of ergot in cattle performance. One trial, led by master’s student Jenna Sarich, fed feedlot cattle concentrations of ergot alkaloids ranging from 0.0 ppm to 3.0 ppm on a dry matter basis. By April, the cattle fed the high-alkaloid diet began to show signs of heat stress, including open-mouth panting, on days that were averaging 17°C to 20°C.
To measure the possible impacts of ergot on blood flow to extremities, the team used infrared imaging to capture the changes in temperature to the ears. The photo shows areas with lighter temperatures [primarily] in the ears, eyes and muzzle (lightest colours).
According to Jenna, susceptibility to heat stress is a result of decreased blood flow to the skin that prevents cattle from being able to dissipate heat. Cattle who were heat stressed also had higher body temperatures, which were measured rectally.
Photo courtesy of Jenna Sarich
Jenna also notes the impacted growth performance. Animals in the high-ergot diet had significantly lower average daily gain (ADG) and dry matter intake (DMI) prior to switching to the ergot-free diet. When the ergot was removed, the poor performance was reversed and steers outperformed the control group, reaching similar weights by the end of the study. Although, heat stress symptoms did persist. Additionally, steers receiving 1.50 ppm had significantly impacted performance (ADG and DMI) by the end of the trial and presence of heat stress as well (although to a lesser extent than at 3.0 ppm).
A second trial at AAFC Lethbridge looked at the combined effects of feeding ergot and DON to 40 feedlot cattle. In the diet containing higher concentrations of both ergot (4 ppm) and DON (10 ppm), the animals showed a 36% decrease in dry matter intake, lost 16% of their body weight and their average daily gains decreased by 55%. Renee Bierworth, a master’s student of Dr. Ribeiro and Dr. Tim McAllister, suggests that the combination of mycotoxins demonstrated some compounded effects compared to feeding ergot or DON on their own.
The results of both trials suggest that the recommended concentrations for both ergot and DON in cattle feed may need to be re-evaluated.
A big challenge for producers in dealing with the threat of mycotoxins is that they are a hidden problem. The presence of fungi or mould is a noticeable indicator of a possible threat, but the mycotoxins themselves are invisible, colourless and odourless, and may be present whether or not ergot bodies are visible. The best way to measure the presence of mycotoxins in feed is to submit samples for a mycotoxin panel and an ergot alkaloid panel.
Laboratories offering mycotoxin testing for livestock feed:
When buying feed, consider asking a feed mill nutritionist:
Do you test product for mycotoxins?
Which ingredients do you test?
How frequent is the testing?
Are all staff trained to oversee incoming products?
Photo courtesy of Beef Farmers of Ontario
Ensuring feed quality also means following best practices:
Practice regular feed testing and mycotoxin screening, remembering visual appraisal is unreliable.
Never feed mouldy feed to pregnant animals.
Purchase cereal by-products from reputable feed sources and test for mycotoxins prior to feeding if you are unsure. (Cereal screenings and distillers’ grains are higher risk.)
Source quality, ergot-free feed from trusted sources (feed mills, feed suppliers, etc., that have strong quality control measures in place).
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