Swine are not exactly grazers. They will eat some grass, but they typically prefer legumes, weeds, roots, and other types of food. Traditionally, pigs were allowed to fatten in wooded areas, where they could make a comfortable living on acorns.
The wild counterpart of the domestic swine, the wild boar, can adapt to a wide range of ecosystems. Pigs share this characteristic, but are not native to North America. They can have a destructive effect on the landscape without proper care.
Swine are not selective grazing animals at all. They will pretty much mow down anything they come into contact with, although grass species do seem to be their least favorite plants to consume. This behavior can be destructive in the wrong place, but it makes pigs good at clearing land, opening up the understory of woodlots, and preventing wildfires by removing brush.
Pigs have snouts like shovels and they love to root, so be prepared for some degree of pasture damage (swine used to have rings put into their noses to prevent this behavior). Smaller breeds will have less impact on the land, turning up only the top few inches of soil. Alternatively, this rooting behavior can be put to good use by allowing the pigs to do your tilling for you.
Animal units are not typically used to determine stocking rates and densities for swine, perhaps because there is limited research in this area. Most sources recommend about 5 to 10 breeding sows per acre, or 6 to 10 young pigs per acre.
Not all pigs are going to be able to meet their nutritional needs on pasture alone. However, they are not ruminants and can therefore digest grain efficiently without adverse health effects. Mature breeding swine should be able to forage for the vast majority of their food, but growing pigs will require generous protein supplementation. Planting legumes such as alfalfa in the pasture will help. Alternatively, consider the traditional method of fattening hogs in a woodlot, where they can root for acorns, grubs, and other high-protein treats.
Be aware that pigs will fatten much slower on pasture than they do in confinement. While this is perfectly normal, given the extra exercise they receive, some producers are caught off guard.
The ideal body condition score for reproducing swine is 3. Sows may fluctuate either above or below this number as they cycle, but should never drop below 2.5.
- Rotational. Some type of rotation is essential if keeping swine on pasture, since they can completely destroy the pasture in a very short amount of time if kept in a continuous system.
A good grazing system for pigs will include a reliable supply of water. Weaners will require only 1 gallon per day, feeders 3 gallons, mature hogs 5 gallons, and lactating sows 6 gallons.
Swine can be either very easy or very difficult to contain, depending on your forethought. They will damage most physical barriers, but will respect electric fencing, so use either electric woven polywire or a physical fence with an offset strand of electric on the inside. If you plan to use electric fencing exclusively, place a single strand at snout height, and check it regularly for debris that might cause a short.
Swine can be extremely destructive in a pasture setting due to their weight and propensity to root. Lighter breeds are easier on pastures. However, if you do want a heavier breed, consider seeding your pasture more thickly than usual to achieve a dense stand that can hold its own. Frequent rotations are a must, and periodic reseeding may be necessary. Alternatively, use your pigs to tear down unwanted weeds and brush in overgrown pastures, along brushy perimeters, or in their favorite setting—the woods.
A unique way to pasture hogs is to use them to till a plot to grow their own feed, and then allow them to harvest it themselves. Let your pigs completely till a paddock, then move them to a different paddock. Scatter seeds of squash, turnips, and other forage plants over the vacated paddock. When the crops are ready for harvest, turn the swine back into this paddock and let them do the work.
Be aware that swine can be very aggressive and may not coexist well in a multispecies system. Pigs should be kept in a paddock to themselves.