Estimation of Forage Intake by Steers Grazing Three Fescue Types and Determination of Alkaloids in Ruminal Fluid and Forage1

During 2 consecutive grazing seasons, DMI of steers grazing 'Kentucky-31'endophyte (Neotyphodium coenophialum-infected tall fescue (E+; Festuca arundinacea Shreb.), 'Kentucky-31'endophyte-free tall fescue (E-), and 'Quantum'tall fescue infected with endophyte AR542, a non-ergot alkaloid-producing strain (Quantum) was estimated using alkanes as markers. The appearance of ergovaline and lysergic acid amide (LSA) also was quantified in forage and ruminal fluid of steers grazing these forages. Estimates of DMI did not differ(P= 0.88) when based on fecal samples collected at 0800 h, 1700 h, or a composite of the 2 sampling times. Estimation of DMI using hand-plucked samples tended to be greater (P = 0.06) than whole-plant clipped samples. Estimated DMI was greater (P < 0.05) on E- pastures than E+ or Quantum across both years. Both LSA and ergovaline were present in E+ forage throughout the grazing season but were not detectable in E- and Quantum. Similarly, LSA appeared in ruminal fluid of steers grazing E+, but not in steers grazing E- and Quantum. Ergovaline was not detectable in ruminal fluid of steers grazing any of the 3 fescue types. These data suggest time of fecal sampling does not affect DMI estimations, but method of forage sampling does. Lower DMI may affect performance of steers grazing E+ and Quantum. Additionally, the appearance of LSA in ruminal fluid of steers grazing E+ suggests that this ergot alkaloid may contribute to fescue toxicosis.