The premise behind management intensive grazing (MIG) is to move a large group of animals across a pasture in such a way as to maintain the grass sward in a semi-stressed vegetative stage of growth all season long. This is accomplished by initiating heavy grazing pressure for a short period of time (hours or at most a few days) followed by a long period (weeks) of total rest. Maintaining grasses in a semi-stressed state results in improving and thickening the overall sward because all grasses grow and reproduce like crazy....and also add root volume like crazy...when they are semi-stressed (ie cut) and then rested on a regular basis.
As you'll learn, cows lend themselves to MIG a lot more readily than horses do for a whole variety of reasons related to natural behaviours and attitude combined with psyiology. In comparison to horses, and especially to the warmbloods and thoroughbred crosses that we tend to board, cows are wonderfully docile animals with low personal space requirements and a very limited desire to act in "spirited" ways. It's natural and normal for cows to crave closeness with other cows; if you put a large herd of cows in a big pasture they will naturally eat their way across it as a tight group. More or less they'll lie down as a group, rise as a group, and move to and from water sources as a group without any human intervention at all. To enact MIG, all we really need to do is add some portable electric fence to control where and when the group moves. Additionally, cows have no top teeth which means they can only eat grass down so far before they're forced to move and find some taller plants on which to munch.
Except in short term turnout situations, true MIG and horses really don't mix very well unless the group is very small and paddocks are large relative to the acreage in question. Horses don't behave like cows in any respect at all. First, unlike cows, horses DO have top teeth and they are spot grazers in the extreme. If they find an area containing some plants they like to eat they will literally graze until the plants are eaten into the ground and they'll keep eating them until they've all dead. Nature abhors bare ground so inevitably weeds take the place of good grass and the weeds will eventually need to be controlled before they take over completely.
Compared to cows, horses need a lot of personal space and if they don't get it they tend to get very snarky with one another as they bite at, kick and chase one another around. This behaviour is kind of fun to watch from a distance but it is HELL on pastures; two or more horses being snarky with one another can tear up a huge areas of grass in an extremely short period of time. Because of their space requirements and their much hotter nature (relative to cows), confining horses to small areas of a pasture for extended periods with either electric wire or tape as is done in true MIG will almost certainly result in injury to the horses and extreme injury to the pasture, even if they are moved frequently.
So instead of true MIG which is practiced with cows and which is designed to enhance the quality of the pasture over time, the idea with horses is to practice a modified form of MIG designed to limit the damage a group of horses can achieve on a given piece of land. The principles of modified MIG can be summarized as follows.
1. Thou shalt confine horses to drylots or put them in the barn during freeze-thaw cycles and during the worst periods of muddy ground in the winter and early spring.
2. We try to keep horses off new seeding and off pastures in the spring time until the grasses have become established. This is a struggle for most pasture based operations and it's easier written or said than actually done. Feeding good quality hay in the early spring can be a big help in accomplishing this.
3. Thou shalt make every effort to control weed infestations while they are still small, and if it's necessary to spray to achieve adequate control thou shalt spray when only a sniff of spray is required to do so. All weeds are most easily controlled at the seedling stage.
4. If it's possible to do so, rotating horses through a few large paddocks allows the grass at least some time to recover with minimal grazing pressure and it'll greatly enhance the life of your pasture while reducing the maintenance required to achieve and maintain a decent grass sward. It's been our experience that horses respond best to paddocks that are considerably longer than they are wide. Perhaps this allows each horse to feel like it has more space than it actually does ??
5. Since horses are very much spot grazers, we use mechanical grazing (mowing with a bush hog) several times a season to encourage the grass to remain in a vegetative state and to encourage horses to graze in a different spot. This gets mixed results but it's a bunch better than nothing which is what most folks around here do.
6. We also incorporate manure with a chain harrow as soon as the ground is fit to work in the spring. Usually we do this at the same time we seed and fertilize, accomplishing three things with one pass of the tractor. In addition to breaking down clumps of manure into usuable organic matter more quickly than would happen naturally, it aerates and dethatches the pasture at the same time, promoting vigourous grass growth.
For those that practice modified MIG at home, I'd sure be interested in learning where your approach differs from ours and in what results you are able to achieve by doing so !
22 hours ago