Ergot: How Much Is Too Much?

Background

The risk of ergot and other mycotoxins is generally highest in years when the weather is warm and humid when grain crops and grasses are flowering. Ergot bodies contain a variety of different alkaloids that can reduce feed intake and growth, cause lameness, gangrene, abortion, weak calves, and greatly reduced milk production. Some alkaloids likely pose more danger to cattle than others. Some alkaloids likely pose more danger to cattle than others. Ergot awareness and concerns are increasing among producers. As cattle are generally believed to tolerate ergot better than pigs or chickens, ergot-free feed grain may be directed to poultry or swine, potentially increasing the amount of ergot that cattle are exposed to. However, it is not understood that cattle can be more sensitive to levels of ergot alkaloids (EA) than pigs and chickens.

Objectives

• Define the composition of ergot alkaloids in cereal grain fed to beef cattle in Western Canada;
• Characterize how ergot is metabolized by rumen microbes;
• Define maximum concentrations of ergot alkaloids that can be fed without impacting beef cattle health and welfare;
• Determine if cattle adapt to continuous doses of dietary ergot alkaloids or if tolerances to ergot are impacted by intermittent exposure and by pelleting it

What you did

These researchers surveyed ergot alkaloid profile in cereal grains from Alberta and Saskatchewan and better defined what levels of ergot alkaloids are safe for feedlot cattle. They conducted an artificial rumen study to look at how ergot alkaloids affected ruminal fermentation and the microbial population. They also looked at how rumen microbes respond when they’re provided very high ergot alkaloid levels (20 ppm) with and without an ergot binder, compared to no ergot. A backgrounding and finishing trial fed diets containing 0, 0.75, 1.5 and 3 ppm total ergot alkaloids to looked at the impacts on growth performance, physiology and welfare (and whether cattle adapt to ergot). A second backgrounding and finishing trial looked at the effects of continuous vs. intermittent exposure to ergot. On top of this, ergot that was ground up and added to the total mixed ration was compared to the same level of ergot fed in pellets to assess whether the heat treatment involved in pelleting helped to reduce the dangers that ergot poses to feedlot cattle.

What they learned

The main EA present as a percentage of total EA across all crops (rye, wheat, triticale, and barley), locations (12 different places across AB and SK), and years (2018-2020) was ergocristine (45.3%) followed by ergotamine (15.5%). There was not much variation in the ergot alkaloid profile due to crop, location, or year the sample was collected. On average R-epimers represented 81.1% of the total alkaloids with S-epimers contributing to the 18.9% left. The maximum and minimum percentage of R-epimers in the samples analyzed was 91.9% and 64.5% respectively.

In the artificial rumen study, EA reduced ruminal microbial diversity and the acetate:propionate ratio. Adding an ergot binder increased total volatile fatty acids (VFA) and reduced total microbial protein synthesis. Although EA slightly reduced organic matter digestibility and acetate production, these negative effects were reversed by the addition of the ergot binder.

In the first feedlot study, steers fed 3.0 ppm of EA were transferred to the control diet (without EA) in the last half of the finishing phase due to toxicity (hyperthermia) as spring weather conditions warmed. As EA levels increased, growth rate throughout the backgrounding and finishing phases decreased, while rectal temperatures increased and altered feeding behaviors occurred. Steers removed from 3 ppm EA diet exhibited compensatory gain, but their respiratory rate remained elevated 50 days after EA were last consumed.

In the second feedlot study, pelleting ergot contaminated grain did not reduce the impact of ergot alkaloids on any of the measured parameters. Results suggest that continuously or intermittently feeding an ergot contaminated diet (2 ppm EA) can significantly reduce intake (7.5 to 10%), growth performance (10 to 20%), and carcass weight (5 to 7%), with minimal impact on blood serum parameters in backgrounding and finishing steers. Pelleting was not an effective method of reducing ergot toxicity.

What it means

Ergot alkaloids had a small impact on ruminal fermentation but these were reversed by the use of the ergot binder. Steers fed EA had lower DMI, ADG, carcass weights, and dressing percentage than steers fed a control diet without ergot. Diets fed to feedlot steers with 3.0 ppm of EA promoted toxicity. Intermittent feeding showed similar results to continuous feeding of EA on reducing intake and growth performance of steers. Pelleting was not an effective method of reducing ergot toxicity. Ergot can impair animal health and performance, even at levels allowed under federal feed regulations.