By Andi Anderson
Beef cattle across the U.S. face serious reproductive challenges due to heat stress and fescue toxicosis. These environmental and dietary factors can reduce productivity and health, especially during hot, humid months.
Heat stress happens when cattle produce or absorb more heat than they can release. This causes a rise in body temperature and signs like heavy breathing, panting, or standing in water to cool off. In 2003, heat stress was estimated to cost the U.S. beef industry nearly $369 million annually.
The Temperature-Humidity Index (THI) is used to measure heat stress risk. According to the University of Nebraska-Lincoln, THI scores fall into four categories:
- Normal: below 75
- Alert: 75–78
- Danger: 79–83
- Emergency: above 84
As THI levels rise, cattle reproduction rates decline. In extreme summer heat, conception rates can drop to 10–20%, compared to 40–60% in cooler seasons. Heat stress also reduces growth, milk production, and overall health.
Fescue toxicosis is another challenge, especially in regions where cattle graze on tall fescue grass infected with toxic endophytes. These toxins cause poor blood flow, increased body temperature, and difficulty in shedding heat. This adds to heat stress and further impacts reproduction.
Combining these two stressors—heat and toxic forage—puts beef cattle at a higher risk of fertility issues. Producers are encouraged to monitor THI, provide shade and water, and consider pasture management strategies to reduce the impact of fescue toxicosis.
Understanding and addressing both heat stress and fescue toxicosis can help improve herd health and maintain reproductive performance during the summer months.
Photo Credit: gettyimages-baranozdemir
Categories: Ohio, Livestock, Beef Cattle