swine & u team

The University of Minnesota parasite research team is made up of (left to right) Dr. Yuzhi Li, organic pig farmer Marissa Callens, University of Minnesota summer intern Tracy Rheingans and University of Minnesota graduate student Maria Lou.

Today’s consumers seek to know the origin of their food, and in response, more and more small and niche farms are raising pigs to supply natural pork or organic pork for local customers. Very little university research has been conducted in this area of pig farming. The University of Minnesota’s Yuzhi Li has investigated alternative feed grains for organic pigs and is now researching the prevalence of intestinal parasites (worms) in organic and pasture-raised pigs, and how to control or eliminate them. (Li’s work is funded by a succession of U.S. Department of Agriculture National Institute of Food & Agriculture (NIFA) grants.)

What is organic?

I was recently given a book, “Swine”, published in 1910 and written by William Dietrich. Dietrich was an associate professor of swine husbandry at the University of Illinois. This textbook covers everything hog producers needed to know about raising swine in the early 20th century. Professor Dietrich referred to worms as “this evil in the swine-growing industry”. At that time, some of the remedies for internal parasites were so severe that it’s remarkable the pigs survived the treatment!

All pigs grown in the early 1900s could have been considered organic by today’s definition. The USDA manages the U.S. organic crops and livestock program and issues certification to farms who meet the organic livestock standards. 

USDA’s organic livestock standards include these elements (from www.ams.usda.gov/organicinfo): Pigs must be managed organically from the last third of gestation. Animals must be allowed year-round access to the outdoors except under specific conditions (i.e. inclement weather). Pigs must be raised on certified organic land meeting all organic crop production standards. Animals must be fed 100 percent certified organic feed, except for trace minerals and vitamins used to meet the animal’s nutritional requirements. Pigs must be managed without antibiotics, added growth hormones, mammalian or avian byproducts, or other prohibited feed ingredients (urea, manure or arsenic compounds). Bedding used in organic livestock must come from organically produced crops (i.e. straw or corn stalks). 

Some vaccines are allowed in certain stages of breeding swine, and breeding sows are allowed to be treated with synthetic de-wormer in the first and second trimester of gestation. 

In organic production, some prohibited substances are allowed if preventative strategies fail and the pigs become ill. Those pigs are not allowed to be marketed as organic after they recover. 

In addition, organic animals must be raised in a way that accommodates their natural behavior. This includes access to outdoors and fresh air; shade and shelter with clean dry bedding; space for exercise; clean drinking water; and direct sunlight.

Meeting the needs of producers

Managing swine intestinal parasites continues to be an obstacle for organic pig farmers because there is a lack of organically-approved options for controlling parasites. Dr. Li’s project has been developed to identify what kind of parasite load exists on organic swine farms, and to determine the effectiveness of some organic-friendly parasite management strategies. 

Li, working with researchers at the Rodale Institute and Kutztown University (both at Kutztown, Penn.), set up a series of parasite mitigation practices to learn how effective these would be for organic pig farmers. 

Manure composting — Manure and swine bedding was amassed into compost piles in January, June, and November to learn what amount of time and temperature is required to inactivate worm eggs. This could be a manure-handling step which could neutralize eggs/larvae and reduce the parasite load on pasture or cropland where the manure is spread. This phase of the study is still underway.

Biofumigation — Brassicaceae is a family of plants which includes mustard, rapeseed, cress and many more. These plants contain a compound, glucosinolate, which, when the plant is chopped up, is transformed into isothiocyanate (ITC). ITC is toxic to bacteria, fungi and nematodes, and has promise as a killer of intestinal parasites in soil. The plants are mulched or pulverized with a flail mower at flowering, when the glucosinolate levels are high. The broken plants are then immediately incorporated into the soil for maximum ITC effectiveness. This part of the study was conducted in summer 2019 and will be repeated in summer 2020.

Grazing biofumigated pastures — This element of the study will take place in summer of 2020. Spring planting of mustard, rapeseed and clovers will provide a summer pasture for rotationally grazing young organic pigs. At maturity, the pigs will be harvested and their livers evaluated for parasite symptoms.   

Parasites in pastured pigs

In July 2019, Li and her team visited nine organic swine farms in four states:  Minnesota, Iowa, Wisconsin and Pennsylvania. On these visits, samples were collected from feeder/growing pigs, finishing pigs, and the breeding herd.  Manure, soil and bedding were gathered at each farm and analyzed for the presence of parasites.

Three common swine worms were identified in the samples collected. 

Ascaris suum — Ascaris is known as roundworm and is a common parasite in pigs.  A pig consumes the roundworm egg from the soil or pasture, after which it develops and hatches in the intestines. It can travel to the pig’s lungs or liver, and a common symptom of roundworm infection is that the pig has a cough.

Tricuris spp — Tricuris is another familiar swine parasite commonly known as whipworm. The pig becomes infected with Tricuris by consuming eggs found in the environment. The worm hatches and grows within the pig and sheds eggs via feces. In adult pigs, this parasite causes decreased growth and thriftiness.

Oesophagostomum spp — Oesophagostomum are a nematode which in swine are common nodular worms. These worms are generally consumed by the pig in the larval form. 

These three are the most well-recognized swine intestinal parasites and are very regularly found in pigs raised on pasture and outdoor settings.  

Fecal sample collection at nine organic farms this summer yielded these results: Eight of the nine farms were infected with parasites. Fifty-six percent of the farm were infected with Oesophagostomum; Ascaris, 78 percent of the farms infected; and Tricuris, 44 percent of the farms were infected.

Sixty to seventy percent of the pigs and sows were infected with Oesophagostomum; Ascaris, 50 percent of the pigs infected; and Tricuris, 25 percent of the sows were infected, 40 percent of the pigs infected.

Sows had higher load of Oesophagostamum than pigs (371 eggs per gram vs. 60 and 176 eggs per gram). Pigs had heavy load of Ascaris (1,733 eggs per gram for feeder/growing pigs; 1,198 eggs per gram for finishing pigs; and zero eggs per gram for sows. Trichuris was found in all stages at a relative low level (55, 67, 79 eggs per gram for sows, feeder/growing, and finishing pigs).

These preliminary results show there is a large variation among farms. Organic farms have a wide variety of management protocols, including deworming within USDA organic standards, and care and cleaning of the barn and bedding environment. Researchers also found a geographic regional variation with the Oesophagostomum being more common in Pennsylvania than the other states investigated.

When considering the effect of parasite infection on pig performance, this study found there is no obvious effect when infection load is low, but younger pigs may be more vulnerable to infection.

This investigation of intestinal parasite prevalence in organic pigs is the first leg of a study which was developed to help organic pig farmers learn how they can reduce or eliminate worms in their herds. Further investigation will continue through 2020. Stay tuned for the results!

Diane DeWitte is an Extension Educator specializing in swine for the University of Minnesota Extension. Her e-mail address is stouf002@umn.edu