Overgrazing Can Hurt Environment,
Your Pocketbook

Ed Rayburn

Extension Forage Agronomist

WVU Extension Service
11/00

This article was published in the November 2000 issue of the WestVirginia Farm Bureau News

Sustainable grassland production is based on grass management, animalmanagement, and livestock marketing.  Grazing management is the foundation ofgrassland-based livestock production since it affects both animal and plant health andproductivity.

Overgrazing can occur under continuous or rotational grazing.  Itcan be caused by having too many animals on the farm or by not properly controlling theirgrazing activity.  Overgrazing reduces plant leaf areas, which reduces interceptionof sunlight and plant growth.  Plants become weakened and have reduced root length,and the pasture sod weakens.  The reduced root length makes the plants moresusceptible to death during dry weather.  The weakened sod allows weed seeds togerminate and grow.  If the weeds are unpalatable or poisonous, major problems canresult.

One indicator of overgrazing is that the animals run short of pasture.  Under continuous grazing, overgrazed pastures are predominated by short-grassspecies such as bluegrass and will be less than 2-3 inches tall in the grazed areas.  Palatable tall grasses such as orchardgrass are sparse or nonexistent.  Soilmay be visible between plants in the stand, allowing erosion to occur.  Underrotational grazing, overgrazed plants do not have enough time to grow to the proper heightbetween grazing events.  The animals are turned into a paddock before the plants haverestored carbohydrate reserves and grown back roots lost after the last defoliation (see table).  The result is the same as under continuousgrazing-tall-growing species die and short-growing species that are more subject todrought injury predominate the pasture.  As the sod thins, weeds encroach into thepasture.

Another indicator is that the livestock run out of pasture, and hayneeds to be fed early in the fall.  Healthy pastures grow until mid-November in WestVirginia.  The potential grazing season lasts into November or longer when wintergrazing management is implemented. If hay feeding is needed in October under normalweather conditions, the pasture probably is being overgrazed.

Overgrazing is also indicated in livestock performance and condition.  Cows having inadequate pasture in the early fall do not have a chance to gainweight after the calves are weaned and may have poor body condition going into the winter.  This makes them hard to winter and may reduce the health and vigor of cows andcalves at calving.  Also, cows in poor body condition do not cycle as soon aftercalving, which can result in delayed breeding.  This can result in a long calvingseason.  With good cow genetics and nutrition, 55% to 75% of the calves should comein the first 21 days of the calving season.  Poor weaning weights on calves can becaused by insufficient pasture in late summer, when cows give less milk and the calvesneed pasture to maintain weight gain.

Overgrazing can increase soil erosion.  Reduced soil depth, soilorganic matter, and soil fertility hurt the land's future productivity.  Soilfertility can be corrected by applying the appropriate lime and fertilizers.  However, the loss of soil depth and organic matter takes years to correct.  Their loss is critical in determining the soil's water-holding capacity and howwell pasture plants do during dry weather.

To prevent overgrazing, match the forage supplement to the herd'srequirement.  This means that a buffer needs to be in the system to adjust for thefast spring growth of cool-season forages.  One buffer many state producers use is toharvest hay in May and June and allow the cattle to graze the aftermath in August andSeptember.

Another potential buffer is to plant warm-season perennial grasses suchas switchgrass, which do not grow early in the season.  This reduces the acreage thatthe livestock can use early in the season, making it easier for them to keep up with thecool-season grasses.  The animals then use the warm-season grasses during the heat ofthe summer, and the cool-season grasses recover for fall grazing.

The grazing guidelines in the table are for rotationally grazed,cool-season forages.  When using continuous grazing, manage pasture height atone-half the recommended turn-in height for rotational grazing to optimize plant health.  The growth habit of some forage species, such as alfalfa, does not permit theirsurvival under continuous grazing.  When managing for legumes in the stand, it isbeneficial to use rotational grazing and graze the stand close and then give adequate restto stimulate the legumes' growth.

Proper grazing management keeps pastures healthy and productive.  This ensures that the livestock using the pastures are also healthy and productive.  To learn more about evaluating pasture condition and animal body condition, contactyour county Extension agent.