The number of cow-calf pairs placed on a pasture is often determined based on previous experience and/or conventional wisdom. One of the factors that easily can be overlooked in establishing stocking rates is cow weight.
Range scientists typically use a 1,000 pound cow with calf as the base definition of one animal unit and cattlemen often use 1,200 pounds to describe the mature body weight of their cows. However, the average mature weight of cows in the U.S. has changed in the last 20 years. If we use feedlot exit weights as a base and the relationship between hot carcass weight and mature dam weight, the estimated mature weight of the 1990 U.S. cowherd was 1,228 pounds compared to 1,386 pounds in 2010 (Table 1). Therefore, using 1,200 pounds for a cow in 1990 was accurate, but today using a weight of 1,350 or 1,400 pounds would be more appropriate. If the total number of animals per unit of land, per month has not been adjusted, then the pounds of animal per unit of land may have increased by about 150 to 200 pounds per animal. This scenario can be referred to as “creeping stocking rate.” For example, a particular pasture supporting 200 cow-calf pairs in 1990, with the cows weighing about 1,200 pounds each, equals a total stocking number of 240,000 pounds. If the number of pairs turned out every spring has not been changed, the actual stocking number today would be 270,000 pounds, an increase of 12.5 percent! This could have serious implications on long-term forage quality and quantity. To get a comparable stocking rate today versus 1990, using 1,350 pound cows, only about 178 pairs should be placed on the pasture.
As many producers make plans for the upcoming grazing season, they should weigh a few cows and give this some thought. It may lead to some difficult decisions, but the long-term sustainability of the forage base may depend on it.
Source: Justin Waggoner, beef systems specialist, Kansas State University