Running Out of Pasture?

When the feed bin gets low, you call and order more fed. If you run low on pasture, the answer isn't so easy. Knowing how much grass is available in your pasture, and how much your livestock requires, is critical to good pasture management.

The first step is to calculate the requirements of your pastured animals. Livestock require 2% to 4% of body weight in dry matter intake. The amount is dependent on the type of livestock and your performance goals. A dry cow on a maintenance ration will require dry matter equivalent of 2% of body weight. A high producing animal such as finishing cattle or lambs, or lactating dairy cows will require about 4% of body weight. For example purposes I will use 3%. Take the number of animals times average body weight to get total number of lbs. of livestock on the pasture. Multiply this total body weight by 3% to get daily dry matter requirements. Example: 50 steers @ 500 lbs. X 3% = 25000 X .03 = 750 lbs. of DM/day.

The second part of this exercise is to estimate the amount of forage that is available in the paddock or field that is going to be pastured. One way of doing this is to estimate how many bales of hay you would expect from the field and use this as the basis for your calculations. There are a number of different measuring devices for determining the amount of forage that is available. One method is to use a grazing stick that assists in calculating the sward density and height to get the available forage dry matter.

A very dense stand of forage will have up to 300 lbs of dry matter per acre-inch of height. (An acre-inch is one inch of height across an acre). A very thin stand will have 50 to 75 lbs of dry matter per acre-inch. An average stand will likely have 100-200 lbs. of DM per acre-inch. To measure height, take the average height across the field. You then subtract 3 inches from the height, as grazing should not be lower than 3-4 inches, this leaves enough leaf area for rapid plant re-growth.

Example - forage is 12 inches tall, minus 3 inches, leaves 9 inches of usable forage in the field. If this was a dense stand this could represent up to 2700 (9x300) lbs. of dry matter per acre. With this number we can go back to the livestock requirement number and determine how many days feed are in the paddock or how big we need to make the paddock for the number of days grazing that are planned. The ideal, from a forage re-growth standpoint, would be only 1 day grazing per paddock. From a practical management standpoint 4 to 5 days is more common. If livestock are in a field for more than 5 days they will start picking off the new leaves of the re-growth. There will also be more tramping loss and damage to the plants if the grazing period is greater than 5 days.

With experience, you will improve your forage estimating skills. These calculations will allow you to optimize the production from your pastures, and better plan for any forage shortfall on the horizon!

| Top of Page |