Fescue toxicity is the most costly grass-related disease in the United States with production losses exceeding $600 million per year. An endophyte fungus within the fescue plant causes fescue toxicosis. This endophyte produces alkaloids that cause adverse symptoms in grazing livestock including: decreased weight gain or even weight loss, reduced milk production, higher body temperature, increased respiration rates, rough hair coat, unthrifty appearance, loss of blood flow to extremities, excessive salivation and poor reproduction.

Research has shown that copper levels are lower in endophyte-infected fescue vs. endophyte-free fescue when grown under identical conditions (See Table 1 and Figure 2).  Additionally, it has been documented that copper levels decrease further in the absence of nitrogen fertilization for both endophyte-infected and endophyte-free fescue (See Figure 1). These findings support observations of decreased copper status in cattle grazing infected fescue. In research conducted in Virginia, cattle grazing endophyte-infected fescue exhibited decreased copper status as opposed to cattle grazing endophyte-free fescue. However, the magnitude of this decrease was greater than the difference between the forages. This demonstrates that the endophyte not only decreases the total amount of copper present in the fescue forage, but also, negatively affects bioavailability of copper for the animal. This makes sense when you consider that the typical symptoms for fescue toxicosis closely resemble those for copper deficiency. These symptoms include rough, discolored hair coats; winter coats that are slow to shed out; decreased conception rates; increased days open; hoof problems; and depressed immunity. For all of these reasons, lowered copper status plays a large part in the fescue toxicosis syndrome.

Table 1. Mineral levels for 50 Tennessee Tall Fescue Samples (taken from Aaron, et. al. University of Tennessee).

Taken from Dennis, et. al. Influence of Neotyphodium coenophialum on Copper Concentration in Tall Fescue. J. Anim. Sci. 1998. 76:2687-2693.

Taken from Dennis, et. al. Influence of Neotyphodium coenophialum on Copper Concentration in Tall Fescue. J. Anim. Sci. 1998. 76:2687-2693.