Cows are classified as herbivores, meaning their digestive system is specifically adapted to break down plant material. However, modern practices of harvesting and processing feed introduce a possibility for insects to be inadvertently mixed into their meals. This accidental consumption is not a reflection of a change in diet, but rather a hazard that can carry significant health risks for the animal.
Defining the Cattle Diet
Cattle are ruminant animals, possessing a complex four-compartment stomach designed to process fibrous plant matter. The largest section, the rumen, functions as a massive fermentation vat where billions of bacteria and protozoa break down cellulose and other structural carbohydrates found in forages. This process converts tough grasses, hay, and silage into volatile fatty acids, which serve as the cow’s primary energy source. The digestive system is optimized for a high-fiber diet. The microorganisms in the rumen also synthesize microbial protein, a major source of amino acids. Because their biology is centered on plant fermentation, cattle do not naturally seek out or intentionally consume insects or other animal proteins.
Mechanisms of Accidental Ingestion
While cows are not insectivores, beetles and other insects can enter their diet through various forms of feed contamination. The most common route is through the consumption of harvested forages, particularly alfalfa hay. Beetles are often present on plants in the field, and the machinery used for harvesting can incorporate them into the final product.
The use of hay conditioners or crimpers during the cutting process is a major contributor. These tools crush the stems of the forage to promote drying, but they also crush any beetles present, mixing the insect’s body and its contents into the hay. Once the beetles are crushed and dried into the baled feed, their presence becomes nearly impossible to detect visually.
Accidental ingestion can also occur during grazing, especially if cattle are eating short forage or grazing near field edges where beetle populations congregate. For cattle consuming green chop or total mixed rations, insects collected during the mechanical chopping of the standing crop can be incorporated into the feed bunk. Since some beetle species are known to swarm, a small area of a field can contain a highly concentrated number of insects, leading to significant contamination.
Toxicity Risks from Certain Beetles
The danger posed by accidental beetle ingestion is primarily associated with the Blister Beetle. These insects contain a chemical agent called cantharidin, which functions as a defense mechanism. Cantharidin is a colorless, odorless, and highly stable compound that acts as a severe irritant and vesicant, causing blistering and inflammation. The toxin remains active even after the beetle has died, dried, and been crushed into the hay.
When consumed by cattle, cantharidin irritates the lining of the gastrointestinal and urinary tracts. Symptoms can range from mild depression and feed refusal to severe gastrointestinal distress, including diarrhea and abdominal pain. Affected animals may exhibit signs of urinary tract irritation, such as frequent and painful attempts to urinate. While cattle are generally more tolerant of the toxin than horses, a sufficiently large number of beetles can still lead to severe dehydration, kidney damage, and death. To minimize risk, producers are advised to cut alfalfa before the bloom stage, when beetles are less prevalent, and to avoid using crimping equipment when beetle contamination is suspected.