Are Genetics the Key to Dealing with Fescue Toxicosis?

Christine Gelley, Agriculture and Natural Resources Educator, Noble County, OSU Extension (originally published in The Ohio Cattleman, Expo 2020 issue)

One of the sessions that I attended during the American Forage and Grassland Council at the beginning of 2020 explored the possibility of identifying genetic markers in cattle for tolerance of the endophytic fungus that lives within the KY-31 tall fescue forage, which is the most prominent pasture grass in our region. This endophyte provides survival benefits to the plant but causes vascular constriction in the animals that can cause mild to severe symptoms and overall reduced productivity.

For decades forage managers and scientists have been working on ways to mitigate the impacts of this endophyte on livestock production. Most successes have come from the forage management side rather than the livestock side. We suggest dilution with other types of forage, rotational grazing, and conversion to novel- endophyte fescues (those containing an endophyte that benefits the plant, without harming the grazing animal).

From observation and record keeping, we know that there are differences in weight gain and health of cattle grazing the same forage in the same amounts in the same location. The question of whether those differences are attributed to environment or genetics, is yet to be answered. It is likely a combination of both.

Some livestock marketers already advertise livestock as being “tall fescue hardy” and they may be correct, but the causes are not fully understood. It could be the location, learned behavior, adaptation, the breed, or the genetic line. In general, any animal (or person for that matter) that changes environments and diets will struggle to adapt at first. The transition period will be smoother from one location to another if the environment is similar. My point being cattle from Ohio will likely perform well in Ohio. Cattle loaded onto a trailer in Florida/Wyoming/Texas will likely struggle to adapt if they are dropped off in Ohio and vis-versa. Environment plays a huge role in this complex system. Management and genetics do too.

The animal science professor presenting at the conference on this topic, gave the audience some hope that maybe there are genetic markers for tolerance. But, that relationship has not been consistently documented yet in the research. If this innovative hypothesis is proven to be true, utilizing those genetic markers for herd management could be another tool in the toolbox for mitigating tall fescue toxicosis and would be significant for the production of grazing livestock in the Fescue Belt of the United States. I am excited to see what develops in the next few years.

In the meantime, I will recommend to you what we do know. Most pastures still contain KY-31 tall fescue. There are manageable concerns with this forage that negatively impact herd/flock productivity. There are steps you can take with the forage and the animals you already have that can make big differences in the herd health and profitability. There are improved varieties available to buy today that you could establish instead to graze. KY-31 tall fescue thrives because it suits our soils and management. We can choose to use it to our advantage through good management or adapt ourselves to something new. There will be challenges, but embracing those challenges often leads to greater success down the line.