Raising pigs outdoors has benefits, risks

Raising pigs outdoors is a requirement in the protocols of many niche pork production programs. This approach is sometimes called “extensive,” as they are contrasted with “intensive” pork production systems where animals are housed indoors throughout their lifetime.

Extensive production of pork is growing in popularity with consumers and entry-level farmers. For beginning farmers, there are lower startup costs associated with facilities, and it is hoped, higher prices received for a specialized product. At Michigan State University, researchers are learning more about the trade-offs and possible combinations of this approach to pork production.

Key Points

Raising pigs outdoors (extensively) is gaining popularity.

Research: More food-borne parasitic pathogens when pigs extensively raised.

MSU research supports new strategies for pork production systems.


One of the trade-offs, which happens to also be a concern, about extensive pork production, is the potential risk of humans becoming infected with Toxoplasma gondii and Trichinella spiralis from harvesting, preparing and eating pork. These are important zoonotic food-borne parasitic pathogens; humans can become infected by these organisms as well. For more information about the symptoms of these infections and recommended meat handling and preparation practices, see the Centers for Disease Control and Prevention website at www.cdc.gov/
parasites.

Disease exposure risks

Research indicates that the incidence of Toxoplasma gondii and Trichinella spiralis in pork is greater when pigs are extensively raised and exposed to cats, which allow exposure to T. gondii, and garbage, wildlife feces and carcasses, which allow exposure to T. spiralis. Researchers from the Ohio State University released results of a study in 2008 in which they tested blood samples from 324 extensive and 292 intensive pigs from farms in North Carolina, Ohio and Wisconsin.

They found the presence of the T. gondii parasite in 6.8% of extensively reared pigs, compared to 1.1% of intensively reared pigs. Two pigs raised in outdoor systems tested positive for T. spiralis. None of the intensively raised pigs tested positive for this parasite. In 2007, researchers from the Netherlands reported a similar trend of higher prevalence of T. gondii and T. spiralis in outdoor-reared swine.

More information needed

The OSU researchers suggest there remains a scarcity of information on the significance of T. gondii and T. spiralis infection associated with extensive production systems. Consequently, in the past few years MSU scientists have started collaborating with Michigan producers to investigate the incidence of infection of pigs raised in various extensive systems. They have taken blood and tissue samples from pigs raised in dirt lots or pastures, grazed in organic fruit orchards, or grazed in vegetable fields postharvest.

To date, they have submitted samples to the Animal Parasitic Diseases Laboratory (USDA Agricultural Research Service, and Animal and Natural Resources Institute) in Beltsville, Md., from five extensive production systems. Preliminary results from 33 samples thus far show T. gondii infection on three of the five farms, but no infection with T. spiralis.

One of the goals of MSU’s work is to evaluate combining extensive and intensive production practices. This past summer at MSU, researchers took 50-pound pigs from the intensive swine facility and raised them outdoors at the Student Organic Farm to a market weight of about 270 pounds. The pigs grazed vegetable fields postharvest, received cull vegetables and trimmings, and were supplemented with a fortified ground corn, roasted soybeans and barley diet. At slaughter, all samples taken from the pigs were negative for T. gondii and T. spiralis.

Admittedly, the 2010 MSU Student Organic Farm pigs are just a small subset of samples, but the findings are contributing to the development of new strategies for pork production systems, where the positive attributes of both extensive and intensive systems may be combined. Faculty and students are learning more about the incidence of these parasites and possible ways the exposure to sources of these parasites can be lessened.

Long term, the collaboration with the Animal Parasitic Diseases Laboratory in Beltsville may provide for new farm-level technology, which may be implemented to reduce or eliminate parasite infection in all pigs.

Rozeboom is a pork specialist with Michigan State University Extension. You can reach him at rozeboom@msu.edu.

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HOGS ON PASTURE: Pigs graze rape in an immature, leafy stage, near Northport in September.

This article published in the February, 2011 edition of MICHIGAN FARMER.

All rights reserved. Copyright Farm Progress Cos. 2011.