June 13, 2008

US study finds antibiotic-free pigs more prone to carry bacteria

Pigs raised without antibiotics are more likely to carry bacteria and parasites associated with food-borne illness compared with pigs raised with antibiotics, according to a new study that was conducted by the veterinary departments of three US universities.

The study found more than half of the pigs on antibiotic-free farms were tested positive for salmonella, while only 39 percent of conventionally raised pigs were detected with the bacterial pathogen.

The presence of the Toxoplasma gondii parasite was found in 6.8 percent of antibiotic-free pigs while it was found in only 1.1 percent of conventionally raised pigs. While the 6.8 percent figure is relatively small, but it is still significantly higher than that of the conventional herds.

Two antibiotic-free pigs were also tested positive for Trichinella spiralis, a parasite that is virtually eliminated from conventionally US pork operations.

The scientists concluded that antibiotic-free pigs' exposure to moisture, vegetation and other animal species may have contributed to their higher rates of pathogen.

Scientists tested pigs on farms in Ohio, North Carolina and Wisconsin. Among the pigs studied, 324 were raised in antibiotic-free systems and 292 raised in conventional farms. The higher rates of infection on antibiotic-free farms were found to be consistent in all three regions.

Funded by a grant from the National Pork Board, this study is part of an in-depth examination of food safety issues in regards to pork production that includes testing pigs for a wider range of disease-causing organisms.

The study was co-conducted by veterinary arms of the University of Wisconsin, Iowa State University and Ohio State University.