Experiment 2. Thirty-six mature (4 to 10 yr old), Angus-Hereford crossbred, nonpregnant, nonlactating cows (399 + 57 kg) were obtained from Dixon Springs Agricultural Center. These cows were culled because they did not become pregnant during a 60-d breeding season. All cows were nursing calves on Acremonium coenophialum-infected tall fescue until 7 d prior to the study. This explains their thin condition.