Proceedings, Western Section, American Society of Animal Science

A study was conducted to determine foraging efficiency of cattle, mule deer, and elk in response to previous grazing by elk and cattle. Four enclosures, in previously logged mixed conifer (Abies grandis) rangelands were chosen, and within each enclosure, three 0.75 ha pastures were either: 1) ungrazed, 2) grazed by cattle, or 3) grazed by elk in mid-June and mid-July to remove approximately 40% of total forage yield. After grazing treatments, each pasture was subdivided into three 0.25 ha sub-pastures and 16 (4 animals and 4 bouts/animal) 20 min grazing trials were conducted in each sub-pasture using four steers, four tame mule deer (deer), or four tame elk during August 1998 and 1999. A bite-count technique was used to determine foraging efficiency and composition of diet. Crude protein content of deer diets tended to be higher (P < 0.20) in pastures previously grazed by cattle; whereas ADF was higher (P < 0.01) and IVDMD was lower (P < 0.05) in pastures previously grazed by elk. Crude protein content of elk diets were not influenced (P > 0.20) by previous grazing, but diet ADF, NDF were lower (P < 0.01) in pastures previously grazed by cattle. Prior grazing did not influence (P > 0.10) intake rates of deer and elk. In response to cattle grazing, cattle and elk diets shifted to more (P < 0.10) forbs and shrub/trees. In response to elk grazing, cattle consumed more grasses; whereas elk consumed more (P < 0.10) grasses and shrub/tree. Deer increased (P < 0.10) shrub/tree intake in previously grazed pastures. This study suggests that early summer grazing by cattle or elk has very little effect on the subsequent foraging efficiency of deer and elk. In addition, early summer grazing by cattle improve the quality of subsequent elk diets, but previous grazing by elk may reduce subsequent diet quality for cattle, deer, and elk.