Effects of Forage Availability on Grazing Behavior of Heifers

Abstract

Effects of decreasing availability of crested wheatgrass (Agropyron desertorum and Agropyron cristatum) on grazing time and biting rate of Angus heifers were investigated. In the first year of the study, as standing crop decreased from 474 to 170 kg dry matter/ha, grazing time increased from 517 to 203 min/day, while biting rate increased from 56 to 64 bites/min. In the second year, as standing crop decreased from 919 to 144 kg dry matter/ha, grazing time increased from 380 to 656 min/day while biting rate increased from 37 to 50 bites/min. Grazing times were similar to those reported in the literature for pastures having much higher levels of available forage. Although grazing times may be correlated with available forage, comparison of grazing times under different pasture conditions are not meaningful unless considered along with other forage and animal factors. On crested wheatgrass pastures, maximum biting rates occurred at lower levels of available forage than reported on tropical pastures.