Sheep Diets and Feeding Behavior in Single and Common Use Grazing Trials on Southwestern Utah Summer Range

A series of grazing trials were conducted on high elevation summer range near Cedar City, Utah . Cattle and sheep were stocked alone and in common in .4 hectare (ha) paddocks. Stocking rates were .76 ha/AUM in 1981 and .60 ha/AUM in 1982. Vegetation measurements were taken before and after grazing treatments to quantify vegetation disappearance. Diet samples were collected from esophageally fistulated sheep in the paddocks before grazing treatments were applied. After a predetermined level of forage utilization was achieved, the paddocks were re-sampled by the esophageally fistulated sheep to examine diets consumed from the forage-reduced vegetation. Behavioral observations were made throughout the trials on sheep grazing alone and with cattle. The length of time sheep spent at a feeding station, feeding station interval, was measured. Sheep ate less grass and more forbs and shrubs than cattle. Cattle showed a strong reluctance to browse snowberry (Symphoricarpos oreophilus) even when the herbaceous vegetation was greatly reduced. Utilization of grasses, forbs and shrubs in the common use paddocks did not represent an average of the utilization by cattle and sheep each grazing alone. Cattle and sheep grazing together used more forage, especially snowberry, than calculated from single use averages. The diets of esophageally fistulated sheep were altered by the various grazing treatments. Diets consumed from previously ungrazed paddocks were higher in forbs, in vitro organic matter digestibility (IVOMD) and crude protein (CP) and lower in fiber than those diets consumed after paddocks had been grazed. Sheep consumed diets higher in IVOMD but lower in CP in paddocks previously grazed by sheep than where cattle had grazed alone or in commonly grazed paddocks. Sheep selected diets from the remaining herbaceous layer when grazing after sheep but ate mostly snowberry when grazing after cattle. Diets of sheep consumed subsequent to common use grazing were intermediate containing both snowberry and grasses. Sheep adjusted their feeding behavior as the grazing trials progressed by increasing the number of brief feeding station intervals. This trend was consistent regardless of whether sheep grazed alone or in common with cattle. However, when sheep grazed with cattle, longer feeding station station intervals persisted further into the grazing trials indicating that amounts of acceptable forage per feeding station were not reduced as quickly as when sheep grazed alone