Dakota Farmer

Converting rents from per acre to animal unit month basis may help you better compare the true cost of grass.

June 5, 2012

3 Min Read

Rental rates for range and pastureland are up an average of 10% in South Dakota, says Ken Olson, SDSU Extension Beef Specialist.

"Increasing demand for corn for ethanol production and growing export markets has increased the price of corn, and the repercussion has been increased costs of virtually all other feedstuffs. Through both direct and indirect influences, this has been an important factor driving land prices and rental rates up, including range and pastureland," Olson says. "This makes renting grass one of many rapidly escalating portions of rising annual cow costs."


Rangeland and pasture cash rental rates for 2012 ranged from $11.65 in southwest South Dakota to $61.95 per acre in east-central South Dakota, according to survey by SDSU economists.

In contrast, when cash rents were reported on a cost per animal unit month (AUM) basis, the range was much smaller ($25.25 to $36.90).


Olson says one concern these figures present is how to compare rental rates on a per acre basis, to rates calculated on an AUM or per animal basis.

The definition of an animal unit (AU) is a 1,000 pound cow with or without a suckling calf at her side.

However, Olson notes that today this is not necessarily an accurate definition because most cows weigh substantially more than 1,000 pound.

"We should not assume that a cow is equivalent to an AU. Bigger cows need more nutrients and therefore additional acreage should be rented for them if they are to receive adequate nutrition to perform well - or run fewer cows on a fixed acreage," Olson says.

He says that a simple, straightforward and accurate way to convert the AU equivalent (AUE) of cattle based on their size is to simply divide the weight of the actual cattle by 1,000 pound to calculate the AUE.

Example: If the average weight of a cattle producer's cow herd is 1,350 pounds, their AUE is 1.35. If they are grazing steers for the summer and their expected average weight during the summer will be 770 pounds, the AUE will be 0.77.

The final term to consider is animal unit month (AUM). An AUM is the forage that one AU will consume in one month.

Olson says a reasonable figure would be 750 pounds of dry matter, which is 25 pounds per day for 30 days.

"If you have an estimate of herbage produced, and assume that only part of it can be removed without damaging the plants -- e.g. 25%- then the appropriate stocking rate in acres per AUM can be calculated that will allow adequate forage to support an AU. Based on the AUE, this can then be converted to acres per animal or pair in the case of cow-calf pairs," Olson says.

Using stocking rate (the ratio of animals to acres), a livestock producer can convert rent per acre to rent per pair easily. Once the conversion is made, the asking rental rate on one unit offered in price per acre can be compared to another unit that is offered on a price per pair basis.

"There are likely to be cases where cost savings can be found once the rental rates can be compared in similar terms," he said.

He adds that another situation where conversion to similar units may be necessary would be when an absentee landowner is more comfortable using a per acre basis and a producer is more comfortable using an AUM basis, or vice versa.

"Being able to quickly convert from one to the other will make negotiations of future rental rates more straightforward," Olson says. "Ultimately, it will help to ensure that the influence of pasture rental on total annual cow costs is managed to the greatest degree possible."

Source: SDSU

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