how do you set stocking rate? four-step procedure: balance supply with demand karen launchbaugh...

How do you set stocking rate?

Four-step procedure: Balance supply with demand

Karen LaunchbaughRangeland Ecology & Management

University of Idaho

4-Step “Forage Demand” Method

1. Calculate usable forage2. Adjust for accessibility (terrain or water)3. Calculate forage demand of animals4. Calculate stocking rate

The forage demand method is used:– When you have no stocking information from

previous years.– To estimate carrying capacity in biological surveys or

land appraisals.– When considering changes in kind or class of animals.

Step 1 - Calculate Usable Forage:Mollie Texan has a ranch in the southern mixed prairie

that is 1,000 acres big. 75% of it is covered by a sandy loam range site that produces 1,500 lb/acre/year. The other 25% is a shallow uplands site that produces 800 lb/acre/year. How much total forage does Mollie produces on her ranch?

Step 1 - Calculate Usable Forage:Mollie Texan has a ranch in the southern mixed prairie

that is 1,000 acres big. 75% of it is covered by a sandy loam range site that produces 1,500 lb/acre/year. The other 25% is a shallow uplands site that produces 800 lb/acre/year. How much total forage does Mollie produces on her ranch?

Step 1 - Calculate Usable Forage: However Mollie cannot use all of the forage she

produces. Why?1. 2. 3. 4.

Step 1 - Calculate Usable Forage: However Mollie cannot use all of the forage she produces. Why?1.Not all the vegetation can be eaten by animals… it isn’t all “forage.”

2. Need to leave some vegetation for soil health.

3. Want to leave some for other animals in ecosystem like wildlife.

4. During the growing season, need to make sure that some leaves remain after grazing so the plants can photosynthesize and recover from the disturbance.

Step 1 - Calculate Usable Forage: Mollie cannot use all of the forage she has on her

ranch. Scientist recommend that Mollie remove only 40-50% of her total forage in order to maintain good range condition. If Mollie decides to use 40% of her total forage, how much usable forage does she have?

Step 1 - Calculate Usable Forage: Mollie cannot use all of the forage she has on her

ranch. Scientist recommend that Mollie remove only 40-50% of her total forage in order to maintain good range condition. If Mollie decides to use 40% of her total forage, how much usable forage does she have?

Step 2- Account for Accessibility Adjustments often need to be made because not all

the available forage on the range is actually accessible by animals.

1. May be too far from water -- it depends on:– Animal species, age, condition and experience– Season of year– Terrain

2. Vegetation may be growing on areas too steep for animals to use easily – it depends on :– Animal species, age, condition and experience

In this example… no accessibility issues.

Mollie has several species that she manages on her ranch. • She has 4 horses that weigh about 1200 lbs each.• She also wants to allow enough forage for 15 pronghorn antelope• The rest of her forage she want to use with sheep that weigh

about 180 lbs each.

How much forage will her horses need for 1 year?

How much forage will the 15 pronghorn eat on her ranch?

How much forage will 1 sheep eat each year?

Step 3- Calculate Forage DemandAn

about 180 lbs each.

We need to determine how many sheep Mollie should put on her ranch. From Step 1 we calculated that Mollie had 530,000 lbs of forage to use.

Reduce this amount by the amount need for horses.

Reduce this amount for the pronghorn:

How many sheep should she stock year long if each sheep eats 1,642.5 lbs/year?

_______ lbs forage ÷ _____lbs/sheep = ____ sheep/year

Step 4- Calculate Stocking RateAn

A proper stocking must include three elements:1. Number of animals or animal units2. Area of land3. Time for grazing

In this example our stocking rate was:282 sheep/1,000 ac/year

Stocking rates are usually described in AUMs (Animal Units Months) as AUMs per acre (AUM/Ac)

or Acres per AUM (Ac/AUM)

What would our stocking rate of 282 sheep/1000 ac/year be in AUMs/Ac?

282 sheep/1000 ac/year in AUM/Ac?• 5 sheep = 1 Animal Unit (AUM) so we have

____ AU’s.• There are 12 months per year so we multiply

___ AU’s by 12 to get ___ AUM’s. (e.g., if you had 1 animal unit for a whole year, you would need 12 AUM’s of forage).

• So we have ___ AUMs/1000 acres, so divide by 1000 to get AUMs/Ac = ___ .

• Or to get Ac/AUM = 1000 ac/ ___ AUMs = ___ Ac/AUM.

What if Mollie decides to stock her ranch with stocker steers instead of sheep?

Suppose Mollie wants to buy steers weighing 600 lbs April 1st and then sell them June 30 when they weigh about 800 lbs.

How much will each steer eat a day (average for the whole period)?

How much will each steer need for the 3 month grazing period?

How many steer should Mollie stock?

What if scenarioAn