Animal performance depends to a large extent on the quality and quantity of forage consumed. Aldrich et al. (1993) fed E+ and E- tall fescues to steers housed at either 22 or 32°C to evaluate response to alkaloids under different environmental temperatures. At 32°C, cattle consumed 22% less feed and 62% more water than animals housed at the lower temperature. Exposure to E+ tall fescue resulted in a significant decrease in serum prolactin levels within 48 h. Digestibilities of dry matter (DM) and of organic matter (OM) were reduced in steers fed E+ tall fescue. Endophyte infected tall fescue hay was fed in differing ratios with wheat (Triticum aestivum L.) straw to steers in an intake and digestion trial (Goetsch et al., 1987). As E+ hay replaced wheat straw, intake declined linearly. Hannah et al. (1990) reported possible inhibition of ruminal fiber digestion in animals consuming E+ seed, therefore providing a possible explanation for the reduced intake observed. Matthews et al. (2005) reported that E+ tall fescue hay was lower in DMI, dry matter digestibility (DMD), and N retention than E- or Jesup MaxQ hays. However, Bush and Burrus (1988) reported no difference in forage quality (see Chapter 11) or DMD of E+ or E- tall fescue forages, and Corrigan (2005) found no difference in crude protein (CP), acid detergent fiber (ADF), and neutral detergent fiber (NDF) of rumen contents of cannulated steers grazing Jesup MaxQ, Jesup E-, or KY-31 E+ tall fescues. Additionally, Burns and Fisher (2006) found hays from tall fescue differing in endophyte status were of similar quality. If forage nutrient content is similar for E+ and E- tall fescue forages, then the difference in performance must be related to DMI and the ingested toxins negatively affecting rumen microbes and/or the physiology of the host animal. Cattle consume more E- and Jesup MaxQ tall fescue than E+. This difference in DMI must be considered when developing grazing systems; in particular, stocking rates of E- and Jesup MaxQ pastures should be reduced by 20 to 25% to enhance persistence of these pastures over those used with E+ pastures. Rotational grazing should provide more control of grazing pressure on E- and Jesup MaxQ tall fescue pastures than the continuous grazing that is used commonly by cattle managers of E+ tall fescue pastures.