Management-Intensive Grazing (MIG) matches the plants need for rest with the animals need for high quality forages. This section covers how to manage the plants to allow them quick regrowth, while harvesting them at peak quality.
Plants get the energy needed for growth from the sun through a process called photosynthesis which occurs in green leaves. In the presence of sunlight, plants use carbon dioxide and water to manufacture carbohydrates (sugars) and oxygen. The carbohydrates supply energy for growth. The greater the leaf area present, the greater the amount of sunlight that is intercepted, with more carbohydrates produced. As the plant grows and leaf area increases, photosynthesis increases to the point where production of carbohydrates is greater than what is needed for plant growth. Surplus carbohydrates are stored in tissues at the base of plants, such as lower stems and roots.
Plant regrowth after grazing depends on energy (carbohydrates). There are two primary sources of energy for regrowth: 1) carbohydrates that are produced by the remaining leaf area and 2) carbohydrate reserves stored in plant tissues at the base of the plant (e.g. orchard grass). Some plants depend more on residual leaf area for regrowth (e.g. white clover and birdsfoot trefoil) while others depend more on stored reserve carbohydrates (e.g. alfalfa and red clover). Grazing management affects both the level of reserve carbohydrates and the amount of leaf area present.
Advantages - Feed quality and palatability are very high.
Disadvantages - Reserve carbohydrate levels are low and regrowth will be slow especially in mid-summer. Additionally, the plant is too short for rapid grazing. The animal will spend too much time grazing and may not be able to eat adequate dry matter to sustain it's production level.
Recommendation - Do not graze at this stage. Allow for a longer rest period.
Advantages - Feed quality of the plants is high and carbohydrate reserves (energy for regrowth) have been restored. Regrowth of these plants should be rapid which will allow for more rotations through the growing season.
Disadvantages - Total dry matter yield has not peaked.
Recommendation - Graze plants at this stage to benefit the plant with ample rest period and the animal with high quality feed.
Advantages - Total dry matter yield is increasing.
Disadvantages - Carbohydrate reserves are increasing but some of the energy is going into the seed and stem production, not the roots for rapid regrowth. Fiber and lignin is increasing in the plant which makes nutrients less available.
Recommendation - As seed heads appear, speed up the grazing rotation to get ahead of the growth, or set aside some paddocks for hay or silage harvest. A key is to harvest the set aside paddocks soon. This will keep them near the same maturity as the other paddocks during the next rotation. Plants that are allowed to reach maturity will regrow much slower.
Advantage - Dry matter yield has reached it's maximum.
Disadvantages - Increasing lignin (undigestible cell wall ) makes proteins, minerals, and digestible fiber less available. Tall plants are difficult for the animal to graze rapidly.
Recommendation - Try not to allow forages to mature to this stage. If they have, mechanically harvest them to allow new growth to begin.
Remember - Animals should stay in paddocks no more than three days to prevent re-grazing of new growth. Attempt to have 2 to 4 inches of leaf remaining in the paddock after the animals are removed. This will increase the rate of regrowth of the forages and increase total production over the year.
It's easy to see why grazing forages in the boot or prebud stage maintains quality and quantity of the plants. However, most forages don't grow at the same rate throughout the year. Use weekly pasture walks to monitor the growth of all paddocks and determine if you need to speed up or slow down your rotation.
As you walk the paddocks, keep your mind open to options you have that maintain pastures productivity. These options include: changing the size of the paddock, changing the length of the grazing period for a paddock, changing the number of animals in a paddock, adding second grazers, adding supplemental feed, using annual forages, grazing hayfields during cry' periods. Flexibility is a goal of successful graziers which allows them to manage most of the change that Ohio weather provides.