Grazing Behavior of Beef Steers Consuming Different Tall Fescue Types and Lakota Prairie Grass

The grazing behavior of beef steers was evaluated using behavior data recorders in 4 sampling periods of 5 d each during June to September 2004. Forage treatments were 'Kentucky-31' endophyte-infected (K31E+) tall fescue (Festuca arundinacea Schreb.), 'Quantum' nil-ergot alkaloid producing endophyte- infected (QNE) tall fescue, and Lakota (LAK) prairie grass (Bromus catharticus Vahl.). There was a weak tendency for steers in LAK to spend more time grazing than steers grazing K31E+ (P = 0.16) and QNE (P = 0.18). Steers grazing K31E+ spent less (P < 0.05) time lying and ruminating and more time standing and idling than steers grazing QNE or LAK. Steers grazing K31E+ had a slower bite rate and took fewer bites and ruminating mastications than steers grazing LAK (P < 0.05). Average daily gain of steers grazing LAK was greater (P = 0.03) than those in K31E+ and tended to be greater (P = 0.07) than QNE. Steers grazing LAK exhibited behaviors supporting greater DMI and better animal performance than those on the K31E+ treatment. Although the behavior of steers grazing QNE was similar to steers grazing LAK, their performance tended to be lower. Performance of steers grazing QNE was not different from steers grazing K31E+. Temperature humidity index values indicated levels of mild or no heat stress during the experiment; however, steers grazing K31E+ exhibited some behaviors consistent with heat intolerance. Temperature humidity index alone may not be a suitable indicator of heat stress in cattle grazing endophyte- infected tall fescue.