Graduation date: 2006
Four studies were conducted on late-summer diet quality and quantity of cattle (Bos taurus), mule deer (Odocoileus hemionus hemionus), and elk (Cervus elaphus) in response to prior grazing by cattle and elk on mixed-conifer rangelands and on related research techniques. In our first study we assessed a photographic technique to estimate shrub browse yield and utilization. Our results indicate the photographic method could be used to measure available browse yield and utilization of shrubs in a nondestructive way. In our second study we compared DMD and NDF digestibility (NDFD) estimates of in vivo digestibility using the following techniques: 1) Tilley and Terry two-stage in vitro, 2) DaisyII in vitro, and 3) filter bag in situ preceded by 48 h acid-pepsin treatment. In most cases, the DaisyII and in situ techniques overestimate both DM and NDF digestibility compared to the in vivo and two-stage in vitro techniques. We compared the bite-count technique (BC) of estimating diet intake and synthesized diet quality to direct estimates of diet quality using rumen evacuation technique (RE) in our third study. In summary, although the BC technique has the advantage of not requiring rumen fistulated animals, for some variables, it did not yield results that were comparable to RE technique. In our fourth study determined late-summer diet quality and nutrient intake rates of cattle, deer, and elk in response to previous early-summer grazing by cattle and elk at moderate utilization level’ (31.9 ± 2.7%) in northeast Oregon. Crude protein level of the animals’ diets did not differ (P > 0.10) on the ungrazed paddock compared to cattle or elk grazed paddocks, however, it was higher (P < 0.10) on cattle grazed paddock than on elk grazed paddock. Cattle diets contained lower CP and IVDMD (P < 0.10) compared to deer or elk diets and relative to elk, deer consistently selected forages which contained higher CP (P < 0.10). Our study suggested that early-summer grazing by cattle or elk at moderate utilization has little effect on the subsequent nutrient intake rate of cattle, deer, and elk in mixed-conifer rangelands during the late-summer in northeast Oregon.