The consumption of N. coenophialum-infested forage leads to mostly deleterious influences on some of the physiological pathways in the animal. Jacobson et al. (1970) reported increased respiration rate (breaths/min) of cattle grazing E+ compared with cattle grazing E- pastures when animals were moved to a barn to collect performance data. Schmidt et al. (1982) reported higher rectal temperatures for steers fed E+ tall fescue seed than for those fed E+ tall fescue hay. This response probably was explained by the higher ergot alkaloid concentration in the seed than in the hay. Siegel et al. (1984) reported that the highest levels of endophytes were found in the leaf sheaths and seed. These findings are supported by research of Jackson et al. (1984) in which graded levels of E+ tall fescue seed were fed to developing beef calves. Differences in feed intake, animal performance, and rectal temperatures indicated that the toxic compounds associated with tall fescue problems were contained in the seed. Rhodes et al. (1991) showed that ergopeptide alkaloids caused peripheral vasoconstriction, which increased heat retention and hyperthermia. Al-Haidary et al. (2001) found that during continuous heat challenge, animals consuming a high level of ergovaline had increased body core temperature as a result of reduced cutaneous heat transfer, rather than increased heat production. Cattle exposed to the alkaloids present in E+ tall fescue have increased respiration rate and hyperthermia, and lower plasma arginine (Oliver et al., 2001). Oliver et al. (1993) used bovine veins and arteries to measure contractile responses induced by selected adrenergic agents. They identified lysergamide as an important alkaloid associated with fescue toxicosis. Recently, Klotz et al. (2006, 2007, 2008) used a procedure similar to that used by Oliver et al. (1993) and found that ergovaline caused a stronger contraction than lysergic acid. Investigators at several locations continue efforts to delineate the effects of alkaloids produced by N. coenophialum on beef cattle.


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