There’s growing pressure for animal agriculture to change its practices, whether it be utilizing gestation crates or feeding antibiotics, but a new paper cautions that these changes may negatively impact food safety.

pigs-inhumane-350.jpgThe discussion paper released by the Council for Agricultural Science and Technology — a research group that includes the Farm Bureau and the American Veterinary Medical Association —  this week identified some of the factors now being discussed that impact animal health, including: antibiotic use, economies of scale, housing, local production and sustainability.

Scientists have long known there is a link between animal health, stress levels and pathogen shedding, but as CAST and others have noted, more research is needed.

“In addition to overtly ill animals, there is a growing body of evidence showing that chronically, previously, and not visibly ill animals are more likely to be contaminated with foodborne pathogens after processing in the abattoir (slaughterhouse),” the researchers write. “These animals, however, may go unnoticed during antemortem (live animal) inspection, and thus questions arise concerning the potential impacts of these animals entering the food supply on public health risk from foodborne pathogens.”

The paper discusses past research that has found animals under stress or sick for a long period of time are more likely to carry key foodborne pathogens, especially Salmonella. Studies have also shown that animals with abscesses or “other significant lesions” that need extra trimming have a greater chance of being cross-contaminated because of the extra handling required.

Many of the buzzwords being discussed in the food movement, and by an increasing number of consumers: “organic,” “all natural,” “antibiotic-free,” or “pastured” have direct animal health implications — many sustainable food advocates argue that these changes lead to healthier animals. But CAST gives some examples of how these methods could have the opposite effect.

Under organic certification, for example, animals cannot be treated with antibiotics or synthetic worm drugs and if animals are based on pasture, these methods directly impact animal health and how production is managed. According to CAST researchers, “increased exposure to the soil and vermin may increase the prevalence of zoonotic diseases in livestock.”

“Various policy changes may negatively impact animal health, resulting in more marginally or not visibly ill pigs, which tips the scales toward reduced public health,” the authors write. “These proposed changes and their consequences need to be considered carefully.”

The paper looks specifically at some research on the difference between keeping animals indoors vs. outdoors:

“Housing livestock indoors can also provide advantages in managing many foodborne organisms. Because outdoor environments cannot be cleaned or disinfected easily, pathogens can persist in the soil, standing water, outdoor structures, and other micro-environments, infecting successive generations of livestock. Other studies have shown that Campylobacter and Salmonella are more common in chickens having outdoor exposure than in birds raised in conventional indoor housing (cages). Dairy cows were shown to be at greater risk of subclinical mastitis when kept in outdoor environments compared with cows kept in barns. According to several studies, outdoor production can also promote infection of the zoonotic parasite Toxoplasma gondii in poultry and swine. This organism has been related in prenatal infections to death or severe brain and eye damage, especially where the mother has not been previously exposed and acquires an infection during her pregnancy.” (Note: For research citations, see the full study).

Researchers also discuss using antibiotics in animal agriculture, a hot topic in the media:

“Antibiotics have a major, positive effect on improving animal and human health. They are used in human and veterinary medicine to treat and prevent disease. Antibiotic use in food animals is highly regulated by the U.S. Food and Drug Administration. The use of antibiotics in food-animal production, however, raises some concerns about antibiotic resistance in bacteria that could affect the efficacy of antibiotics in the treatment of human infections. Concern about antibiotic resistance is not equivalent to actual risk. Resistant bacteria were present long before antibiotics were discovered and found in many places without livestock exposure.”

The FDA, however, has stated very clearly that certain “injudicious” antibiotic uses in agriculture are a public health risk. In its most recent guidance on the issue, the agency cited dozens of studies on antibiotic use and antibiotic resistance. 

The full CAST paper, “The Direct Relationship between Animal Health and Food Safety Outcomes,” can be read here.