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Pastured Pigs — A Primer

By Tamara Scully

Raising livestock on pasture isn’t new, but with the advent of confine­ment livestock operations and the industrialization of meat production, chickens, cows and pigs were moved inside and shut off from the natural world. Feed, water, pharmaceuticals and intensively managed animals liv­ing in man-made environments some­how became the norm. Getting these animals back outdoors has become the goal for many farmers, as well as consumers.

Many issues associated with con­finement — manure management, odors, water pollution, disease due to crowded conditions — are the result of too many animals and not enough space. Likewise, managing livestock on pasture means respecting the limits of the land, understanding the ani­mals’ natural behaviors and properly managing both.

“As with any other livestock, out­door pigs, when not appropriately managed, can elicit damage to their environment,” said Silvana Pietrose­moli, research associate, North Caroli­na State University, Alternative Swine Research and Extension Project.

piglets drinking
Young pigs with portable waterer in a tall pasture system at Fortner Farm in Moravian Falls, North Carolina.

Pigs root in the soil, and this natural behavior is often maligned as the reason pigs aren’t able to be pastured successfully. But rooting behavior is controllable and can be beneficial to pastures, too. Wallowing is another pig behavior which can have detrimental environmental consequences. Soil compaction is another concern, and pigs produce a lot of manure.

All of these issues can be allevi­ated if stocking density, stocking rate and length of time in a given area are managed. What are some best man­agement practices to alleviate soil and water concerns while allowing pigs to exhibit their natural tendencies? How can producers raising swine on pasture become better stewards of the land, avoid odor concerns and raise healthy animals?

Environmental Impact

Pietrosemoli, along with Dr. James T. Green, have been conducting field trials on outdoor swine systems, with funding from a Natural Resources Conservation Services (NRCS) Con­servation Innovation (CIG) grant. The focus of the grant is to “look at ways that we could manage the vegetation and the soil disturbance,” associated with outdoor swine operations, Dr. Green said.

They have identified three types of outdoor swine operations: man­aged pastures, swine habitat, and dry lot models. Each has a different goal and comes with its own management challenges.

In the dry lot system, pigs are on ground with no vegetation and are fed grain. In the swine habitat system, the pasture is managed to reduce soil runoff, nutrient loss and to protect soil health; but the animals are not using pasture to meet their nutritional needs. In the managed pasture sys­tem, intensive grazing provides at least some nutrition, while protecting soil health and decreasing negative environmental impact.

black pigs in field

In each system, soil and nutri­ent runoff, water contamination and damage to soil health need to be minimized, while allowing pigs to ex­press their natural behaviors. Proper positioning of watering systems, fenc­ing, feed availability and even using mulch, toys and food to direct where certain behaviors occur can all help.

“Increasing the number of animals without controlling the stocking den­sity will deteriorate the vegetative ground cover — either in woodlots or in open land: this is the initial stage for the occurrence of bare soil ar­eas, erosion, soil compaction, nutrient leaching and runoff,” said Pietrosemo­li. “Pigs cause soil damage via rooting and trampling.”

Without ground cover, paddocks are prone to runoff and excessive nu­trient loads. Vegetative buffers, which need to be more extensive the less the ground cover in the outdoor area, are necessary to capture runoff. Plant­ing a crop to be harvested in areas where pigs have been can capture excess phosphorus. If the paddock is simply left to regrow as pasture, nutri­ent overload may persist. Limiting the number of pig cycles in a non-vegetative area prior to planting and harvesting the area, and allowing rest and regrowth in vegetative settings before restocking, is essential.

“The runoff from pig paddocks could carry soil particles, soil nutri­ents, pesticides, veterinary medicine residues and even pathogens to wa­ter courses,” said Pietrosemoli. “The creation of buffer zones, establishing strips 16 to 160 feet wide of vegeta­tion along streams and water courses can help.”

When hooves compact soil — known as poaching — drainage be­comes limited and runoff and erosion occur. Poaching greater than 2 inches deep, or the existence of areas with ac­cumulated sediment, runoff in ditches or drainage channels, or channels and gullies in the paddocks indicate that the area is overused, and pigs need to be removed. Debarked trees in wooded areas and exposed roots also indicate damage is occurring.

Sloped areas are more prone to erosion, and slopes greater than 7 percent should be avoided for out­door hogs. Outdoor pig areas should also be located at least 165 feet from wells or springs and 35 feet from water courses to prevent pollution of drinking water sources, Pietrosemoli said. Soil damage due to compaction increases in wet conditions.

Depending on your goal, vegeta­tion can be selected for forages, for being trample- and root-resistant, or both. Forages include clover, alfalfa, ryegrass, brassicas, millet and Sudan­grass. Annual plants are more suscep­tible to damage, and perennial grasses with rhizomes and stolons can best handle the hog traffic.

Outdoor Pig Logistics

Pigs don’t like electric fencing, Dr. Green said, but they do root around fence lines, and preventing soil build­up on the fences is imperative. The re­sulting berms which the pigs will build up can also be advantageous, and can help to contain runoff, if paddocks are properly contoured to the land.

Watering systems for outdoor pigs are tricky, as the pigs will want to congregate near water tanks. They burrow under tanks and concrete pads, seeking moist, cool areas. Using geothermal fabrics or other materials to discourage wallowing near water­ers can cause harm. Perforated hard surfaces large enough to support the entire hog are needed in these areas, Pietrosemoli said, to protect feet and prevent soil damage. Chronically wet areas will also damage pigs’ feet.

More than one waterer per pad­dock is needed to decrease the impact on any given area. Underground lines can prevent freezing in winter and keep water cool in the summer. Por­table watering and feeding systems can help to minimize damage in any particular area.

pigs at feeder
A round feeder over a perforated platform serves to protect soil and feet in a high-use area at A-D farm in Sampson County, North Carolina.

Having an intermittent sprinkler or misting system away from the drink­ing water helps minimize and direct wallowing and keep the animals cool. Wallowing is necessary to help cool pigs, but can damage soils and cause runoff concerns, so directing it to areas of the paddock where it can do less harm and reducing the opportuni­ty to wallow near waterers is essential.

Pigs produce about 80 pounds of manure for each 1,000 pounds of animal, an amount greater than cows. Producers can influence where the manure is deposited. Adding hay or other organic matter to an area can increase the depositing of urine and feces in that area, and the material can later be composted. To spread manure more evenly, move shade structures, water and feed station and shelters periodically.

“As pigs tend to deposit their ma­nure in certain areas, ‘hot nutrient spots’ can be created. The nutrients that cannot be used by the vegetation present the risks of escaping the sys­tem toward surface or underground water courses, thus polluting them and contributing to the process of eu­trophication,” said Pietrosemoli.

In any outdoor pig operation, whether pigs are actively pastured or not, designing the paddocks to man­age wallowing and rooting damage is imperative. Preventing feed loss is also important.

Breed Selection 

Selecting a breed of pig for pastur­ing means finding animals which have more of the traits needed for living outdoors and foraging for their sup­per. Traditional breeds are better ac­climated to the natural environment, and either a traditional breed, or a cross-bred animal, is probably a better bet than a modern purebred, accord­ing to Pietrosemoli.

“You need a hearty forager pig,” she said. “The best pig for outdoor conditions should be adapted to the environment, the available feed re­sources and to the management strate­gies implemented by the farmer.”

Some characteristics to seek in your pastured pigs include: foraging ability; weather hardiness and ability to withstand the sun’s rays (pigs can get sunburn, and white animals are very susceptible); disease resistance; and docility. If you are breeding, mothering ability — as well as breed­ing performance — is important.

Another factor not to be over­looked is marketability. Meat quality matters, and knowing your market before beginning a pastured pig op­eration is a must.

Grazing System Design

NRCS guidelines for pasturing swine recommend 75 percent vegeta­tive cover, with a heavy use area mak­ing up no more than 15 percent of the pasture. The disappearance of veg­etative cover, areas of impacted and disturbed soil, compaction, manure accumulation and trails throughout the paddock are indications that the paddock is overcrowded or overused.

“The presence of denuded and compacted areas is one of the initial indicators that the system needs ad­justments,” said Pietrosemoli.

Producers can use paddock forage height as an indicator for rotation, or they can observe the amount of time rooting versus grazing or other ac­tivities. An increase in rooting signals that rotation is required. Maintaining a higher vegetation height can mini­mize soil damage.

Grazing pigs means paying atten­tion to stocking rates and stocking densities, just as with any other live­stock. Rotational grazing for pigs has to take into consideration the animals’ dietary needs and natural behaviors.

Rotational grazing systems, de­signed around a central sacrifice/ heavy use area, can work very well in outdoor hog systems. Depending on the life stage, the density of the animals will vary. As the animals mature, paddock size can be adjusted accordingly.

The central sacrifice area includes housing, watering and feeding areas, wallowing areas and bedding. This in­frastructure should be moved periodi­cally to minimize damage to soil. Ap­propriate rest periods between groups of animals, both to minimize parasite load and allow pastures to recover, is warranted.

Pig Behavior

“I think that the principles to man­age other livestock species can be applied to managing pigs, without forgetting the behavioral and physi­ological difference among them,” said Pietrosemoli. “The major difference is the rooting behavior expressed by pigs. This can have a great impact on different kinds of vegetation — digging up roots — and soil structure and com­paction. Guided pig rooting activity could be beneficial for weed control or soil tillage and fertilization.”

rooting pigs
Pigs rooting in a paddock at Center for Environmental Farming System (CEFS) Cherry research farm in Goldsboro, North Carolina. Moving pigs before vegetation coverage drops below 75 percent is one means of preventing soil damage and addressing runoff concerns in outdoor hog environments.

Rooting can be good for soil tilth, weed control and fertilization, but managing rooting is essential to reap its benefits. As forage cover decreases, rooting activity increases. If pigs are hungry, rooting will increase as well. Some pigs are more prone to root­ing and may not be manageable in the herd. Consistency with routine is important in decreasing rooting behaviors. Sows like to root in fresh paddocks. Adding hay and distracting them can decrease this initially in­tense rooting routine. Rooting can be targeted to a given area by planting a crop to encourage this behavior, such as forage turnips.

While pigs need some supplemen­tal feed, they also need encourage­ment to forage. If feed is too readily available, they won’t bother. Some re­striction of feed, about 20 percent for growing-finishing pigs, is desirable to encourage foraging — but rooting will increase if feed is too restricted. Also, the greater the percentage of forage contributing to the diet, the lesser the negative impact the system will have on the environment.

“Besides the reduction in produc­tion costs, an additional benefit of the inclusion of forages in diets for pigs is the diminution of the potential for environmental pollution as the consequences of lower amounts of nutrients imported into the system,” said Pietrosemoli.

Pigs aren’t ruminants and can’t utilize the fiber in forages as cows or sheep can. But when pigs are pastured, biological changes occur in the gastrointestinal system, includ­ing changes in microbial population, enzyme levels and even the system’s morphology. These changes make fi­ber nutrients more digestible. Older sows are able to get the most nutri­tional benefit from forages — about 50 percent of the daily nutrient re­quirements. Young pigs are only able to get 10 percent of their nutritional needs met via pasture. Pigs are very selective grazers and can influence the makeup of pasture plants.

“Pigs can be kept in the same pad­dock with other animal species. When grazing mixed species, the productiv­ity of the pasture would improve,” said Pietrosemoli. “In addition, dif­ferent livestock species have different physiology, grazing behavior and for­age preferences, and this would help control unwanted plant species.”

Grazing heifers and sows might even beneficially influence weight gain and parasite load in heifers, she said. While cows won’t graze near ma­nure, pigs do just fine eating the dung path. Other animals are compatible with pigs, too, although horses may have a tendency to fear pigs.

“Pigs on pasture are highly selec­tive, choosing what plants and even what plant part they will consume. This behavior lets them combine dif­ferent feedstuffs to satisfy their nutri­tional needs. As pigs are very selective of the vegetation they will eat, theycan also stimulate changes in the bo­tanical composition of pasture.”

pigs in pasture
Pigs in a multispecies grazing system at Coon Rock Farm in Hillsborough, North Carolina.

Wildlife concerns when pasturing pigs include threats from large preda­tors. Alligators, snakes and hawks can also be of concern, particularly with young animals, as are coyotes, foxes, bobcats and badgers. Feral pigs can introduce diseases and potentially interbreed.

“There is always the chance that keeping outdoor pigs could produce a potential nuisance to neighbors due to dust, smell, noise, drainage prob­lems, insects, pests or vermin,” said Pietrosemoli. “If the stocking rate established is appropriate, with a rest period for forage re-growth in the paddocks, no offensive odors should emanate from the operation. Avoid­ing the accumulation of manure is the best way to control smells and flies.”

The basic tenets of pig behavior dictate that responsibly putting pigs on pasture, without detrimentally im­pacting soil or water, or causing odor concerns, means closely managing their environment. Whether you want feeder pigs to have some outdoor ac­cess or intend to develop a farrow-to-finish operation on pasture, knowing the basics of pig behavior and nutri­tional require­ments and designing an environmental­ly-friendly out­door hog op­eration to meet your goals is possible, prac­tical and pro­ductive.

Pastured Pigs: Stocking Rates

If your goal is to maintain a vegetative cover and pasture your pigs, allowing them to receive some of their nutrition from forage, here are a few basic prin­ciples for selecting breeds, and maintaining appropriate stocking rates.

Stocking rate — the number of animal units per acre — differs from stocking density. Stocking density takes into account the length of time the animals are in any given area. If you are using a full acre of land, with 10 pigs, your stocking rate is 10 pigs per acre, as is your stocking density. But if you are rotationally grazing that acre by dividing it into ¼-acre paddocks, your stocking rate will be the same (10 pigs per acre) while your stocking density will change. Your stocking density is now four times the stocking rate, or 40 pigs per acre. How you manage your grazing can make a difference in determin­ing the best stocking rate for your operation.

Stocking rate also isn’t one size fits all. It depends on the vegetative growth available, the size and breed characteristics of the ani­mals, soil, drainage and even climate. And animal management skills play a role, too.

According to Pietrosemoli, basic guide­lines for stocking rate of pastured hogs are best based on the amount of nutrients de­posited on the soil. In Europe, it is common to define stocking rate based on a maximum accepted nutrient load.

“For beginning farmers, I would recommend starting with a low stocking rate and gradually increasing the stocking rate when their knowledge of the production system, and their skills, grow,” she said.

Referential Stocking Rates to Maintain Vegetation Cover

Annual species: 10 to 20 weaned to finishing head per acre/2 to 4 sows + litter per acre.
Perennial species: 15 to 30 weaned to finishing head per acre/6 to 8 sows + litter per acre.
Natural vegetation: 4 to 10 weaned to finishing head per acre/.5 to 1 sows + litter per acre.
Note: Stocking rates must be adjusted according to forage species, climate, soil, drainage, management and managers’ skills.


Information from the Alternative Swine Unit, Center for Environmental Farming Systems, North Carolina State University
Design of rotational grazing paddocks for hogs
Traditional breed characteristics
Dirt Hog by Kelly Klober, available from Acres U.S.A.

This article appeared in the November 2016 issue of Acres U.S.A. magazine.

Acres U.S.A. magazine is the national journal of sustainable agriculture, standing virtually alone with a real track record — over 45 years of continuous publication. Each issue is packed full of information eco-consultants regularly charge top dollar for. You’ll be kept up-to-date on all of the news that affects agriculture — regulations, discoveries, research updates, organic certification issues, and more.