Stocking Density and Observing Pasture Health

Jun 10, 2022

Overstocking or understocking pastures can lead to many different problems to arise. During the warmer months when pastures are ready to be grazed, having a grazing plan will help farmers effectively use their pasture. Pasture health revolves around three main categories: weed control, pasture rotation/grazing plan, and understanding stocking rates of your pasture.

Weed control is important for your pasture’s health and for your animal’s health. When there is room in the soil density of your pasture that gives weeds the opportunity to grow and take over. The University of Minnesota recommends early weed control as the key method for controlling weeds in a pasture. The cost of weed control will only increase the taller the plants get.

Persistent weed infestations in pastures can:

Reduce the quantity of forage left available for grazing.
Decrease the stand life of desirable forage species.
Impair the functionality of fence lines.
Negatively affect nutritional quality and palatability.

Scouting your pasture for weed types is a worthwhile task for a farmer. Once the weeds are identified you can then use weed control methods to decrease the population. Animal health will be compromised with the increase in weed population. Some varieties of weeds including water hemp and bracken fern are poisonous if consumed by livestock. Certain toxins found in weeds can cause abortion, weight loss, reduction in animal performance, and death.

Once weeds are controlled, creating a grazing plan is the next step in pasture health. In a grazing plan, there are three different types of grazing systems a farmer can put in place. Finding the right system for your operation is a step in creating a good plan. Understanding one type of grazing system is not the best option over another.

Cattle Grazing Management Systems;

Continuous grazing is a grazing method where livestock have unlimited grazing access to a single pasture. Advantages: minimal overhead cost and less management. Disadvantages: uneven manure distribution, weed growth, uneven pasture use, lower stocking rate, and more forage is lost from trampling.

Simple rotation grazing is moving cattle between two to three pastures. Advantages to this system: allows for pasture rest and regrowth, better manure distribution, and 20% increase in forage production and pasture condition compared to continuous grazing. Disadvantages of this method: higher fence and water system cost, and lower forage production and pasture use than intensive rotational grazing.

Intensive rotational grazing is moving cattle between many pastures. Advantages: better weed and brush control, reduces the need for harvested forages, 30-50% increase in the forage production and use per acre compared to continuous grazing, stocking rates may increase, and more even manure distribution. Disadvantages: requires more management, requires close monitoring of forage supply, and higher initial cost for fence and water system.

Once you have found the grazing system you want to put in place the next step is understanding the stocking density of your pasture. This is the difference between the amount of forage your livestock need versus the amount of forage in the pasture.

When figuring your stocking density keep in mind that understocking and overstocking may happen. If this occurs, adjusting your grazing plan is needed.

Understocking: setting the stocking rates too low, leading to a less productive pasture.
Overstocking: setting the stocking rate too high, leading to a reduction in desirable plant species.

Sample calculation for stocking rate:

Calculating dry matter intake per day:
- (Weight of animal) lbs x (percent of dry matter needed/day) x (# of animals) = lbs DM/day
Calculating days on pasture:
- (lbs of forage/acre) x (# of acres)/(Daily herd forage requirement)= Days on pasture

Cattle consume 2-4 % of their body weight in dry matter each day. Let’s say the average weight in our herd is 1,400 lbs, and there are 10 cows. How many days can the cattle graze a 5-acre pasture producing 2500 lbs DM with these 10 cows?

1,400 lbs x 0.04% x 10 = 560 lbs DM/day
2500 lbs DM x 5 acres / 560 lbs DM/day = 22 days

Horses consume 2-3% of their body weight in dry matter each day. Let's say we have 5 horses with a weight of 1,400 lbs. How many days can they be on a 5-acre pasture that produces 2500 lbs DM?