Overgrazing - Graziers Most Common Mistake
by Denice Rackley
“Overgrazing pastures is by far the most common mistake made by graziers,” says Dr. Greg Brickner, veterinarian and grazing specialist with Organic Valley.
“Pasture and livestock health are both impacted by overgrazing on several levels.” While there is no hard and fast rule for pasture management and rotational grazing, making decisions based on the nutritional needs of the animals and the plants results in the greatest benefits for all – animals, soils, and plants.
Plants Harmed by Overgrazing
When pastures are overgrazed, by not moving livestock soon enough or entering pastures too soon, we rob plants of their energy reserves and negatively impact their ability to make energy Brickner points out.
It might have been a few years since you sat in biology class talking about how plants grow; here is a simplified refresher. The roots take up nutrients and water from the soil, the leaves soak up sunlight and take in CO2, then turn that into energy (sugars) within the plant (photosynthesis) and release oxygen into the air.
Think of the leaves like solar panels. More growing leaf area equals more energy for the plant. If you destroyed solar panels that energize your house, you would be in trouble and run out of energy. The same goes for plants. When they don’t have adequate leaf area, they can’t turn sunlight into food – for themselves or for those animals that eat plants.
The living leaf area is proportional to the root mass. This means that the larger clumps of grass have more roots. When plants are overgrazed, not only is the leaf mass decreased, their roots die also.
This double whammy makes it twice as hard to survive. If the plant does survive, it requires more time to grow back than plants with adequate leaves and roots.
Overgrazing Impacts Soil Health
Soil microbiology is also negatively impacted by overgrazing. Dying roots can’t contribute to soil life the same way as healthy, living roots. Fewer nutrients are made available to the soil biome. The organisms that depend on roots for their homes are displaced or die. The carbon sequestration activity in plants is also diminished. Compromised root systems can’t inject as much atmospheric carbon into the soils.
Overgrazing weakens plants, making them more susceptible to heat, drought, floods, insects, and other stressors. Without the leaves to provide shade or root systems to hold the soil together, soil temperatures rise, and soils erode from wind and rain.
The entire biological system begins to suffer from the cascading impact of overgrazing.
Animal Growth and Health Dependent on Proper Pasture Management
“Matching feed quality to animal’s specific needs is where proper pasture management has a positive impact on stock health and our bottom line,” Brickner says.
“Nutritional needs of livestock vary significantly depending on their stage of life.” Young, growing animals and those that are raising young have the highest nutritional requirements. Young, growing forages are calorie-dense, making them ideal for growing or lactating stock. Animals in the later stages of pregnancy also benefit from prime forage.
Animals that are mature or not bred can be maintained on fewer calories. This enables mature open stock to meet their needs by grazing more mature forage. Brickner also points out that dairy stock and small ruminants require a higher plane of nutrition than beef cattle.
Animal health is impacted by more than just nutrition. “Intestinal parasites are normal in the livestock biome but an overabundance of parasites can impact animal health. Parasite control comes down to pasture management,” Brickner notes.
Livestock that is continually exposed to parasites and is nutritional compromised will be most vulnerable. “Not grazing pastures below 4 inches limit the exposure to parasites.” Allowing rest periods between grazing enables the grass to recover from the previous grazing and can interrupt the parasite life cycle. However, Brickner cautions, “extended rest periods can lead to mature forage which contains high amounts of fiber but seldom meet growing animals’ nutritional needs due to decreased sugar content.”
Smaller paddocks and moving animals frequently is the system that Brickner uses on his own farm where he lambs out 200 ewes in April. “We time lambing so that pairs hit the surge of spring grass at the end of April. Daily moves ensure fresh grass that contains the most nutrients for the lactating ewes while avoiding removing too much leaf area from grasses and parasite pressure.”
Brickner prefers to keep paddocks small and utilize the forage to feed the sheep rather than the soil. “Trampling biomass does serve to mulch soils and can help maintain biodiversity.” The quick rotation of livestock distributes their manure, urine, and even saliva more evenly. These moves better serve the soil community by distributing nutrients in readily useable forms.
Keeping forages in a vegetative state by grazing with quick rotations has another added benefit, “actively growing plants with healthy root systems add more carbon to the soil than trampling,” Brickner notes.
Set Stocking and Stored Forages as Management Tools
Brickner points out that there are two additional pasture and animal health management tools that graziers often overlook - set stocking and stored forages. “Stored forages are a great management tool. Having forages on hand enables producers to adjust to conditions beyond their control.” In drought, extended rain events, or unexpected snows, stored forages enable timely decisions that improve both pasture and animal health.
Set stocking can be done successfully without overgrazing Brickner points out. “Set stocking works well when the stocking rate is matched to grass growth. Maintaining 6 inches of growth enables grasses to withstand consistent grazing pressure while avoiding added parasite pressure.”
Rotational grazing, by itself, doesn’t ensure overgrazing will not happen.
Balance Needed
Balancing the needs of the grass and livestock is no easy task. Each year brings weather changes that complicate matters. Brickner suggests that following a few general recommendations will help maintain both pasture and animal health –
1. Maturity of forage indicates grazing readiness.
Grazing based on maturity, rather than simply judging by height, will help maintain the quality and quantity of forage.
- Perennial grasses are ready to graze when they have 3 full leaves.
- Tall fescue can have 2 full leaves.
2. Height doesn’t necessarily correlate to maturity or indicate the plant has adequate energy reserves to withstand grazing pressure.
Forage height is influenced by species, climate, and fertility.
3. Don’t get caught up in following the latest and greatest advice from everyone.
It’s best to match advice with what your individual operation needs.
4. Keeping in mind pasture feed quality and animals’ stage of production that dictate their nutritional needs.
5. Maintain pasture biodiversity. Incentivize less utilized areas of pasture with shade, water, mineral.
6. Allowing long rest periods continually may negatively impact biodiversity. Grasses can mature, crowding out other species and forbes.
7. Stockpiling forage can be used for winter grazing of mature stock. If different areas are stockpiled yearly can be done without harming biodiversity.
8. Stored forages enable flexibility and timely management of pastures and animals.
Grazing cover crops
Bales ready for winter bale grazing
Proper pasture management requires catering to the specific needs of the animals that are grazing. Maturity of forage and leaving sufficient leaf surface to maintain plants’ energy reserves and root mass need considered when grazing to avoid overgrazing and to optimize pasture health.
By graziers consciously considering the nutritional needs of livestock while keeping in mind the energy needs of plants, a wonderful balance can be achieved where soils, plants, and animals all benefit.
