by Jesse Bussard
Well, it’s official. My thesis defense date is scheduled for August 30th. I’ve been busy this week working on getting my final presentation together. I’m hoping to knock the socks off my advisory committee with this seminar. In preparation for this I thought it would be a great idea to share with you, my readers, what I’ve been working on over the past year and a half that I’ve been slaving away in graduate school.
My thesis project evaluated two very different methods of measuring vascular changes in cattle that had been grazing and then removed from endophyte-infected (E+) tall fescue. If you’re not familiar as to why this is an issue, I encourage you to read more about fescue toxicosis here and here. It’s a big problem for the cattle industry, with over 25% of our nation’s beef cowherd affected (estimate from a recent survey I completed). This merits a need for continued research in ways to manage and mitigate its effects on the cowherd.
To better help you understand how this forage became so widespread (over 14 million hectares currently) in use I’ll give you a basic rundown. Let’s take a trip back in time…
In the early 1800s, tall fescue was introduced to the United States via settlers from Mediterranean Europe who along with their many belonging, also brought grass seed. Test plots were planted in several states.
It wasn’t until 193os though, that tall fescue would make it’s mark on agriculture. In 1931, on the farm of William Suiter in Menifee County, Kentucky, Dr. E. N. Fergus, an agronomist from the University of Kentucky, a unique biotype of tall fescue that was both persistent and productive was found on a steep hillside. Dr. Fergus was impressed with the forage and obtained seed from the biotype which later went into variety test plots at UK’s research farm. From there, this led to foundation seed production and commercial release of the popular tall fescue cultivar ‘Kentucky 31′ in 11943 (named for the state and year that the biotype was discovered).
Tall fescue is well adapted to the humid areas of the southeastern United States in the transition zone, also known as the “Fescue Belt. ” As you can see in the diagram below, this zone extends from the temperate northeast to the subtropical southeast and as far west as Oklahoma and Kansas.
This forage has many agronomic advantages including wide adaptation to environments, persistence under a wide range of management systems, good forage yield, a long growing season, and excellent seed production. While this is so, it also exhibits some undesirable qualities, which can be seen in the lackluster performance of livestock grazing this forage.
These anti-quality factors are attributed to the production ergot alkaloids produced by the fungal endophyte (Neotyphodium coenophialum) that lives in a purely mutualistic association with the plant residing intercellularly in leaf and stem tissue. Researchers have estimated that approximately 95% of all tall fescue pastures in the U.S. are infected with the endophyte.
Several alkaloids isolated from tall fescue have proven to be biologically active, but the major toxin produced in culture was ergovaline. The symbiotic relationship of endophyte and grass imparts the fungus with a reliable source of nutritents, protection, and propagation, while improving the plant’s capacity to survive drought, insect pests, and mammalian herbivory (grazing).
The endophyte was discovered by a USDA-ARS scientist, Dr. Joe Robbins, in 1976. This discovery led to the development of endophyte-free (E-) cultivars in the 1980s. Initially thought to be a godsend to livestock producers with the forage showing increased animal performance in grazing livestock. However, as the use of the E- cultivars grew, it became apparent that they lacked the stand persistence, drought tolerance, and resistance to environmental factors that their E+ counterparts possessed.
More recently cultivars containing beneficial (novel) endophytes have been released. These beneficial endophytes increase plant persistence and resistance to disease and pests without the negative effects of ergot alkaloids on animal performance. While novel endophyte varieties are not widely used yet, they are gaining in popularity and provide a valuable too in the management and mitigation of fescue toxicosis for livestock producers.
Next week I will explain the effects of fescue toxicosis on the cardiovascular system of cattle and how my graduate research is helping to find more effective ways of evaluating this.
As always, if you have any questions or comments, feel free to leave a comment below or email me (email@example.com). I’ll do my best to get you the right answer. Thanks for reading!