Proper Grazing Management

Jeff Goodwin
Rangeland Management Specialist
Blackland Prairie GLCI Coordinator
USDA-Natural Resources Conservation Service

             Texas ranchers are having to make some harsh ranch management decisions with the fluctuating highs and lows in fuel and fertilizer prices, cattle markets, etc.  Some aspects of this issue can be controlled while others cannot.  The cost of a barrel of oil and the price per ton of phosphorus are beyond management control, however there are some aspects of management that can be controlled.  Consequently, the economic bottom-line is affected by these management decisions.

Grazing management is one of the decisions managers can make.  Choosing where, when, how much and how often livestock graze can optimize economic reward.  Whether the ranch is rangeland or introduced permanent pasture, setting proper stocking rates and grazing management is the place to start. 

            Warm season perennial grasses, both native and introduced species, make up the largest portion of our grazing resource in Texas.  Warm season perennial grasses, like all green plants, utilize the photosynthetic process to produce food to survive.  This is the world’s most efficient “Green Energy” producer.  This process occurs in the above ground leaf material.  Thus, the main function of the plant’s leaf is food production.  These grasses derive 95% of their food from the atmosphere via photosynthesis, through their leaves. Think of the leaves as “Solar Panels”, providing energy for the plant.  Only approximately 5% of their need is derived from the soil.  The plants roots and crown serve as the “storage warehouse” for the plant’s food reserve. The stored food in the roots is utilized by the roots themselves for root development.  This enables the plant to survive stress periods.  The energy stored in the crown provides reserves for spring green-up until enough “solar panel energy” is produced to take over the food production business of the plant.   Plant roots are also used for plant stability and water/mineral uptake.

            Warm season perennial grasses are very efficient food producers, producing about double of what they need to sustain themselves.  Thus, from a grazing management standpoint, about half of the current year’s production can be “taken” without any adverse effects to the plant.  Studies indicate, if half of the plant is removed, root development is not negatively effected.  However, if 70% of the plants production is removed, half of the root growth is stopped for 17 days (almost 3 weeks).  If 90% of the top growth is removed the situation is much more bleak: all root growth is stopped for 17 days!  During this period of time the roots are shrinking as they are using up their stored reserves for survival.  Root development is crucial to the health and vigor of this year’s plant health and next year’s production.  Deep roots mean survival!

            This concept laid the foundation for the old “rule of thumb” take-half-leave-half.  Utilizing about half the annual production ensures that the plant will continue to be healthy, vigorous, and productive.  The key however, lies with the utilized 50% of the plant.  This means half of the key plants, not half of all the plants in the pasture!  Therefore, the Natural Resources Conservation Service (NRCS) embraces the “25% Harvest Efficiency” method for determining stocking rates on rangeland.  Studies have shown a cow will consume about 25% while another 25% will be lost due to trampling, insect damage, other grazing, etc. which together totals the 50%.  Therefore, in actuality only about 25% of the total forage produced (in a proper grazing management plan) is grazed by the cow.

Proper grazing management is essential to sustaining the resource

Photo credit: Natural Resources Conservation Service

            These concepts are very important to remember when setting stocking rates on grazingland.  Two things are required to set a stocking rate, an accurate assessment of annual production (lbs/ac) and animal demand (lbs forage needed/animal/year).  There are many methods of determining annual production; however the simplest way is to start by getting a yard stick.  Across the pasture at several representative locations, clip a one square yard plot to the ground.  Bag the forage from each clipping and allow to air dry for 48-72 hours. Once air-dried, weigh each sample with a gram scale and average the weights.  Multiply this average by 10.7 to get pounds/acre.  This method works on rangeland and pastureland.

            Once annual production has been estimated, determine animal demand.  Animal demand is the pounds of forage needed by one standard animal unit (AU) or 1000 lb. cow and calf per year.  An animal unit will eat about 10,950 lbs of forage per year to sustain one cow and calf.

            Now that the annual production and the animal demand are known, the stocking rate can be calculated.  For example purposes, assume 4000 lbs of forage/ac. Utilizing the 25% Harvest Efficiency method, 1000 lbs/ac would be the allowable forage.  To calculate the stocking rate; divide the Animal Demand (10,950 lbs/animal unit/year) / Allowable forage produced (1000 lbs/Ac) which equals a stocking rate of 10.95 Acres per Animal Unit or Acres/1000lb cow. The actual figure will need to be adjusted depending upon rainfall and flexibility.

            The last step in setting a stocking rate on rangeland is factoring grazable acres.  There are areas in pastures that cattle do not graze such as steep topography, heavy brush, headquarters, gravel roads, etc.  Remove these areas from the stocking rate calculation to reduce the risk of overgrazing.  For example, assume 30% of the pasture is not grazable. Divide (10.95 Acres/AU) by (70% grazable acres), which leaves a final stocking rate of 15.64 Ac/Animal Unit or 15.64 Ac per cow. Not compensating for the percentage of ungrazable pasture is a common mistake when setting stocking rates. 

            On average, about seventy percent of the warm season grasses’ production is produced by July 1st.  This period is a good time to “take a look” at your pastures to monitor how closely animal demand is balanced with forage production.  Another time to monitor the production is at frost. This provides insight into the amount of forage available to make it until spring green-up. 

As today’s input costs keep increasing, a balanced grazing management plan can reduce the reliance on purchased feeds.  It is still important however, to provide supplemental feed during the times of the year forages naturally fall below animal needs.   Minerals and salt are also necessary to provide a balanced diet for the livestock.  For more information on grazing management, contact your local USDA-NRCS field office.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age,  disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or part of an individual's income is derived from any public assistance program.