Think of pasture as a feed bunk

By Gary Sliworsky
Ag rep, Emo

The following is the first of a two-part article on determining the amount of forage you have available on pasture for your livestock.
Pasture is a feeding system. Like any feeding system, it is important to know the needs of your livestock and the amount of feed you are offering.
Think of your pasture field as a feed bunk.
When feeding in a bunk or manger, you offer your livestock the quantity of feed they need to get to the next feeding while maintaining feed quality at the highest possible level.
Estimating the pounds of feed on a pasture may seem like a tall task, but it is important if you are going to achieve the potential of the pasture and livestock.
There are two steps to this process:
1. Determine the nutritional needs of your livestock.
2. Determine how much forage is available for grazing each day.
Step 1—Determine livestock requirements
The nutritional needs of livestock generally are calculated in terms of dry matter (DM). Dry matter intake of three percent of body weight frequently is used for growing and producing livestock.
For example, a 1,200-pound cow requires 36 pounds of DM per day (1,200 × 0.03) while a 1,500-pound cow requires 45 pounds of DM per day (1,500 × 0.03).
This may be slightly more than their actual needs, but it allows for some feed refusal.
If we take the total weight of the herd multiplied by three percent, we get the feed required per day on pasture.
Step 2—Determine pasture available
The second step is to determine how much grass or forage is available on a given area for the livestock to graze.
This can be done by one of three methods:
•Grazing stick
A grazing stick enables you to measure the height and density of the grass by how visible the stick is on the ground.
Using a table of height and density printed on the stick, you then can estimate the forage DM available.
•Rising plate meter
An 18-inch square plexiglass plate, 1/8th-inch thick, is used to slightly compress the grass to a constant density.
The height of the compressed grass then is measured and a chart is used to estimate the DM available per acre.
When calculating the amount of forage in the field, remember that you want to leave three-four inches of residue to re-grow and start the development of the grass for the next grazing cycle.
Subtract this three- or four-inch height from the total height to get the usable height.
Next week will look at a third way to measure the amount of pasture, as well as a method for calculating the head/acre/day.