The key principle in determining proper stocking rates for range or pasture is balancing the amount of forage required with the amount of forage that can be removed while making sure that the long-term health of the grazing land resource is not compromised.  While we often focus on the plant communities and how healthy and productive they are, we also need to make sure that we’ve made the proper calculations on the demand side.

The standard measure of forage intake and requirement has been the Animal Unit (AU). The Animal Unit Month (AUM) is the forage quantity required by that animal unit for a month.  We’ve also used $/AUM as a benchmark to compare rental rates in range and pasture rather than $/acre because the AUM measure takes out differences in rainfall and productivity between various regions.

We typically think of an AU as being equal to one cow and her suckling calf.  Does that assumption fit with the reality of many of our cowherds today?  The NRCS definition of an AU is one mature 1000 pound cow and her suckling calf.  It’s not uncommon at all to find herds with an average mature weight of 1200 to 1400 pounds with some individuals higher than those weights.

It’s important that we consider how our cow sizes have changed over time as we determine and make adjustments to stocking rates.  For example, perhaps we’ve always stocked a particular unit with 60 pairs.  If our average cow has increased by 200 pounds from it was in the past, we could find ourselves in a situation where the stocking rate should be reduced to maintain the health of that grazing resource.