Lesson Plan 7:
Stocking Rate Calculations

Background Information

Rangelands are areas of land with predominantly native vegetation made up of a mix of grasses, forbs (or wildflowers), and shrubs. Rangelands vary in their ability to produce vegetation because of different underlying soil types, amounts of moisture received, and health of the vegetation due to past management practices. Rangelands that have been moderately to lightly grazed, have soils with more organic matter, and which receive more rainfall will have healthier vegetation capable of producing more forage (an amount measured in pounds/acre or kilograms/ hectare).

Cattle and sheep are the predominant domestic grazers on Montana's rangelands, but big game wildlife species (such as elk, deer, and antelope) graze these same areas as well. It is important that ranchers manage how many of their animals will graze in each pasture, taking into consideration use by wildlife species, so the rangeland is not over-grazed and the vegetation remains healthy and productive for grazing each successive year. Ranchers manage so that livestock do not consume all of the forage that is available, but use a general rule of thumb to take half and leave half of the forage by weight. By leaving a portion of the forage, the remaining stubble allows those plants to maintain root reserves for survival throughout the winter and slows water movement the following spring, reducing erosion.

Although the total land area may be covered with vegetation, there are some considerations to make regarding whether livestock or wildlife will use certain portions of the land. For cattle, these considerations are slope of the land and distance from water, and for elk these considerations include distance from cover and roads. The value that different types of vegetation have to the diet of cattle and elk (or grazing merit) determines its palatability (tastiness) for each animal. When calculating stocking rate, or the number of animals grazing an area of land for a certain amount of time, consider 100% of the forage available for those plant species with good grazing merit, 50% for those with fair gazing merit, and 0% of the forage weight for those plant species with poor grazing merit.