Performance of lactating dairy cows fed tall fescue forage.

Two trials were conducted during consecutive summers to compare performance of lactating cows fed four varieties of tall fescue soilage. The first trial was conducted in 1983 and the second in 1984 using 25 midlactation Holsteins. Treatments included endophyte-free Kenhy; 8.1% endophyte-infected Johnstone (a prevarietal release); endophyte-free Kentucky 31; 63% endophyte-infected Kentucky 31; and orchardgrass or alfalfa as controls. In 1983, concentrate was fed twice each day at the rate of 4.1 kg per feeding, and in 1984, 4.5 kg were fed twice daily for first 4 wk and 4.1 kg per feeding thereafter. Intake of Kenhy was higher than all other tall fescue treatments when data for both trials were combined. Means of the high endophyte Kentucky 31 group were lower than all other treatments during both trials for milk yield, dry matter intake, body weight change, and serum prolactin in 1984 while higher for rectal temperature. Improved intake and performance of the cows consuming Kenhy compared with those consuming endophyte-free Kentucky 31 indicated the improved forage quality of this variety. Decreased performance of dairy cows consuming endophyte-infected tall fescue, even at a relatively low infection, was evident.