Table 1 -Threshold levels fo ergovaline and lolitrem B in the diet that produce clinical disease. Two studies conducted on steers at the OSU Agricultural Research Center in Burns evaluated the effect of feeding high-endophyte tall fescue straw. Each straw ration was supplemented with alfalfa pellets at 0.5 percent of body weight. The level of ergovaline in the diet had no effect on weight gain in either study. Heart rate, respiration rate, and rectal temperature were not influenced, and no health problems were observed.
Straw is less digestible than seeds or grass, both of which produce classic tall fescue toxicity.
The lower digestibility of straw may reduce the risk of toxicity. A series of studies at OSU in Corvallis indicated a possible subclinical effect from ergovaline. Sheep fed grass seed screenings containing levels of ergovaline from 50 to 600 ppb showed decreased average daily gain. Also, as levels of ergovaline increased levels of the hormone prolactin in the blood decreased. Avoiding endophyte toxins Pastures planted with certified seed of Oregon-grown forage varieties of tall fescue or ryegrass should be safe to graze or cut for hay.