Fescue Toxicos - A Stealthy Threat to Cattle Health

By Andi Anderson

Tall fescue, a common grass in the transition zone of the US, can harbor a hidden enemy: the fungal endophyte. This fungus, while beneficial to the plant, produces toxins called ergot alkaloids that wreak havoc on cattle grazing in the pasture. This article explores the various ways fescue toxicosis impacts cattle health and productivity.

Summer Slump: The Heatwave of Toxicity

The most common manifestation is "summer slump," a heat stress nightmare for cattle. Ergot alkaloids constrict blood vessels, hindering the body's ability to cool down. Cattle spend more time panting and idling, grazing less and losing weight. Milk production, calf weaning weights, and reproduction all suffer as a result.

Fescue Foot: Gangrene at the Extremities

In some cases, the blood vessel constriction takes a more sinister turn, leading to "fescue foot." This condition affects the hooves, ear tips, and tail, causing swelling, lameness, and even tissue loss. It's a painful and debilitating consequence of chronic exposure to ergot alkaloids.

Fat Necrosis: A Hidden Threat Within

Less common but equally concerning is "fat necrosis," where hard masses of dead fat develop in the abdomen. These can obstruct vital organs, causing digestive problems, weight loss, and even birthing difficulties. This often goes undetected until necropsy, highlighting the insidious nature of fescue toxicosis.

Diagnosis and Defense: Unmasking the Toxin

Diagnosing fescue toxicosis requires a combination of clinical signs, pasture analysis, and potentially, ergovaline testing of forage. Unfortunately, there's no blood test for the condition.

Management strategies include:

Limiting exposure: Rotating pastures, reducing grazing time on E+ (endophyte-infected) fescue, and providing alternative forages can help mitigate the impact.

Novel endophyte varieties: Newer fescue varieties with reduced endophyte levels offer a promising solution.

Replacing E+ fescue: In extreme cases, replacing the infected pasture with other forages might be necessary.

Fescue toxicosis is a silent thief, stealing cattle health and productivity. Vigilance, knowledge, and proactive management are key to protecting your herd from this insidious threat. By understanding the signs, diagnosis, and management options for fescue toxicosis, you can safeguard your cattle and ensure their well-being.

Photo Credit: gettyimages-prill