Effects on Growth Rate and Digestibility

Consumption of E+ tall fescue or treatment with tall fescue extract caused a reduction in rate of gain and feed intake in cattle (Schmidt et al., 1982; Hoveland et al., 1983; Bond and Bolt, 1986), rats (Neal and Schmidt, 1985), and rabbits (Daniels et al., 1984). No reduction in growth rate was observed in yearling horses when corn-based concentrates were used to supplement E+ or E- hay (McCann et al., 1992). Pendergraft and Arns (1993) observed similar gains in yearling horses consuming E+ or E- hay with concentrate supplementation to meet NRC requirements for growth. However, average daily gains were reduced by 57% (0.24 and 0.56 kg for high- and low-endophyte treatments, respectively) in yearling horses grazing E+ pasture without supplementation, with a reduction in gain similar to that observed for steers in the same study (Aiken et al., 1993).

Redmond et al. (1991) and McCann et al. (1992) observed lower intake and digestibility for E+ hay fed to mature geldings and yearling horses, respectively. McCann et al. (1993) and Pendergraft and Arns (1993) found no differences in digestibility due to presence of the endophyte in hay when yearling horses were fed concentrate with the hay. Concentrate supplementation was used in both studies to meet NRC requirements for growth for yearling horses These results suggest that the effects of endophyte consumption on digestibility and growth rate may be lessened by the inclusion of concentrates in the diet. In contrast, energy supplementation has no beneficial effects for alleviating lactation and reproductive problems in gravid mares that graze E+ tall fescue pastures (Earle et al., 1990).


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