(Lesson 6. Managing for a Year-Long Forage Supply continued)
Rotational grazing, management intensive grazing, and Voisin grazing are terms that describe a system of grazing where animals are introduced to new feed on new paddocks on a frequent basis. Animals are confined to relatively small paddocks to maximize efficiency in grazing. In this system, high quality forage is rationed out to meet livestock needs, while plants that have recently been grazed are protected from being eaten again until they have adequately recovered. By managing animal access to forage, you are managing plant growth and plant health. The factors that you control that are important to a successful rotational grazing program are intensity of grazing, duration of grazing, resting or recovery period, and size and number of paddocks.
Intensity of Grazing
Intensity of grazing is the term pertaining to the amount of the forage mass removed or grazed from a pasture during the grazing period. Tall growing species should be grazed at different heights than low growing species. Grazing should start in a paddock when vegetation is 6 to 8 inches high for tall growing species such as timothy, orchardgrass, bromegrass, and reed canarygrass and 4 to 6 inches high for low growing species like bluegrass, redtop, fine leafed fescues, sweet vernal, and white clover. For rapid regrowth and to maintain a healthy stand, animals should be removed when the forage height is reduced to 2-3 inches for tall growing species and 1 to 2 inches for low growing species. One exception to these height recommendations is the first time a pasture is grazed in the spring. Grazing of tall species should start when new spring growth reaches 4 to 5 inches in height and stopped when the stubble height is about 1.5 inches. Grazing of low growing species should start when new spring growth reaches about 3 inches and stopped when the stubble height is about 1 inch. Move the animals rapidly through all the pastures to establish a staggered forage regrowth pattern necessary for the rest of the grazing season. Another exception is when soils are so wet that punching is a problem. Delay grazing until the soils are dry enough to support the weight of the animals without punching. Charts are available to determine how much forage is available from a pasture (See Lesson 1, Appendix D). Tools such as pasture sticks, rising plate meters, and other electronic devices are also available.
Duration of Grazing
The length of time that animals have access to an individual paddock is referred to as the residency period. The residency period should be as short as possible to prevent animals from grazing regrowth. Plant regrowth may begin in 3 to 4 days in May and June but may not begin for a week or longer during July and August when the weather is hot and dry. The more often livestock are moved to fresh grass, the more uniform the quality and quantity offered. Lactating dairy cows should be provided with a fresh paddock after each milking for optimum milk production, but could stay in one paddock for up to 3 days. Beef cattle, heifers, dry cows, and other animals can graze on a single paddock for 3 to 4 days, but no longer than 6 or 7.
Resting or Recovery Period
The interval of time a pasture is allowed to regrow after grazing is the resting or recovery period. This resting period is crucial for high forage production from pastures. The frequency at which a pasture is grazed controls the quality and quantity of feed that is produced. Pasture growth rates are always in a state of flux. Pasture growth rates are very high in spring and early summer. During the heat of summer, pasture growth rates tend to be the lowest. Thus the resting or recovery period will vary with the seasons. Pastures should be grazed as often as every 10 to 15 days in the spring, 15 to 20 days in late spring and early summer, and 25 to 30 days during summer and fall.
Size and Number of Paddocks
Forage production, number of animals, and length of residency period are all used to calculate size of paddocks. Forage production values for different soils are available from local NRCS offices. Paddock number is dependent on how frequently animals are moved. The more frequent animals are moved the greater the number of paddocks that are needed; 12 to 36 are needed in spring and midsummer and 24 to 84 are needed in midsummer to fall. In actual practice, farmers must make day to day decisions about adjustment to the rotation lengths and paddock size and number. Portable electric fencing makes adjusting of paddock size and number easier. Contact your local University of Maine Cooperative Extension county office or the Natural Resources Conservation Service for help in setting up a rotational grazing system.
However, even with rotational grazing, cool-season plant growth is slow during summer and pastures may not produce adequate supplies of forage. Often in July and August animals are grazing whatever they can find.
How do we manage to have enough high quality forage available from July through fall? To accomplish this, cool-season pastures need to be destocked after spring (less animals per acre or longer rotation lengths because less forage per acre is being produced). How do we go about destocking? There are several ways to do this. One is to stock pastures lightly. Forage growth will get ahead of grazing animals in spring, but animals will be able to selectively graze and there will be more forage for later in the growing season, although it will be of lower quality. This is a viable option for some livestock operations. However, animal production per acre will be below its potential.
Another approach to destocking pastures in summer is to make hay on some pastureland in spring and then use those fields for grazing in summer. This results in more acres for grazing during summer (destocking). This system allows for both hay production and for extra pasture during slow growth periods.
In beef systems you can over-winter calves, graze them the following spring, and move them to a feedlot or sell them as plant growth slows. This option has to be weighed against the cost of feeding animals over winter.
Another way to destock pastures is to remove animals altogether. Using more than one type of forage crop for pastures may give the best chance of supplying adequate amounts of forage season long. Several alternatives for additional crops and management strategies for pastures are discussed in the next section of this lesson.