Prolactin is a hormone normally associated with milk secretion in cattle. Hurley et al. (1981) first associated the presence of toxins in tall fescue with the inhibition of prolactin secretion. Since then, decreased serum prolactin levels have been reported by nearly all investigators working with E+ tall fescue. Strickland et al. (1993), Thompson and Stuedemann (1993), and Oliver (1997, 2005) have published excellent reviews of the effects of N. coenophialum on prolactin, other hormones, and endocrine functions in cattle.

Evidence of oxidative stress in cattle consuming E+ fescue during heat stress has been measured by the shift from glutathione to oxidized glutathione concentrations (Lakritz et al., 2002). The combination of heat stress, reduced feed intake, and thermoregulatory effects found in cattle grazing E+ tall fescue may induce oxidative stress.


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