In 2008 I posted, “Grass-Fed vs Grain-Fed Beef and the Holy Grail: A Literature Review,” in which I raised the question if grass-fed beef is safer that grain-fed. My concern was, as I said, that Quotes like these were becoming more common on the Internet and recent media reports:

“Products from grass-fed animals are safer than food from conventionally-raised animals.” Eatwild, 2008

“Research has shown that the strains of E. coli most devastating to humans are the product of feedlots, not cows. This is due to the animals being forced to eat an unnatural diet, and not their natural choice, grass.” Grass-Fed Beef: Safer and Healthier, Animal Welfare Approved, June 15, 2008

My conclusion of the literature review was: In summary, the scientific evidence at this time does not support a broad conclusion that grass feeding significantly reduces the risk of E. coli O157:H7 or other dangerous foodborne pathogens from entering the food chain. However, more research is needed to better understand the influence of diet, especially the use of different types of grains in animal feed.

Now a recent abstract entitled, “Contamination Rates and Antimicrobial Resistance in Bacteria Isolated from “Grass-Fed” Labeled Beef Products” by Jiayi Zhang, Samantha K. Wall, Li Xu, Paul D. Ebner in Foodborne Pathogens and Disease, once again puts into question the conventional wisdom that somehow grass-fed cows are safer than grain-fed cows. Here is the abstract in part:

Abstract: Grass-fed and organic beef products make up a growing share of the beef market in the United States. While processing, animal handling, and farm management play large roles in determining the safety of final beef products, grass-fed beef products are often marketed as safer alternatives to grain-finished beef products based on the potential effects of all-forage diets on host microbiota.

We conducted a series of experiments examining bacterial contamination rates in 50 beef products labeled as “grass-fed” versus 50 conventionally raised retail beef products.

Coliform concentrations did not differ between conventional and grass-fed beef (conventional: 2.6 log10 CFU/mL rinsate; grass-fed: 2.7 log10 CFU/mL rinsate). The percentages of Escherichia coli positive samples did not differ between the two groups (44% vs. 44%). Enterococcus spp., were frequently isolated from both grass-fed beef products (44%) and conventional beef products (62%; p = 0.07). No Salmonella or E. coli O157:H7 isolates were recovered from any of the meat samples. Enterococcus spp. isolates from conventional beef were more frequently resistant to daptomycin and linezolid (p < 0.05). Resistance to some antimicrobials (e.g., chloramphenicol, erythromycin, flavomycin, penicillin, and tetracyline) was high in Enterococcus spp. isolated from both conventional and grass-fed beef.

There were no differences in the percentages of antimicrobial resistant E. coli isolates between the two groups. Taken together, these data indicate that there are no clear food safety advantages to grass-fed beef products over conventional beef products.

Perhaps more research is still needed. The sample size of this recent study was small. Perhaps Food Safety News should do a larger one?

  • Ken

    The other considerations for grass vs grain looks at nutrtional quality grain fed are higher in fat content which most people associate with better flavor and texture and greenhouse gas generation. The article below is based on a study done in Australia which suggests that grain fed beef is “greener” because the concentration of feeding allows faster weight gain and less methane generated. The results are discussed pretty articulately in the comments. Proving once again there are no answers without consequences some of which are deliberately sought and some of which are unexpected.

  • JaneKay

    Wouldn’t a lot of this contamination depend more on the slaughter and packing plant anyway? For instance, pretend that I am the most meticulous of all ranchers raising healthy, robust, completely organic grass-fed cattle or bison. Then, the company that slaughters my animals and packs their meat is negligent or even reckless in their handling of it (they are a USDA plant in a big hurry). My “special” meat could then become the next recalled product due to no fault of mine in raising them. Is that not correct? By the way, who actually selects the meat processing/packing plant, the rancher who raises the animals or the company that buys them and markets their meat?

  • No, the nail is far from driven. Once an idea takes hold (vaccines cause autism, IUDs are dangerous, DDT is unequivocally bad, anxiety causes ulcers), it is hard to remove it from the realm of things “commonly known to be true.”
    Combine that with how appealing the idea is, that is, how much people want it to be true, and it becomes clear that it takes more than a scientific proof or publication in peer-reviewed journals to refute it.

  • BillM

    Oh boy, a whole 50 samples. Now let’s wait for some serious peer reviews.
    In the meanwhile, let’s consider the realities of conventional animal food production: 1000s of animals packed into confined spaces for months at a time in some cases, fed diets that cause gastrointestinal stress, ulcers and other digestive tract illnesses, then the processing of these animals at a rate of up to 3000 per day, and you have the recipe for serious contamination. Add to that the conventional practice of continuous dosing of the feedlot animals with antimicrobial drugs to stave off infections from the bad diets (and to unnaturally increase their growth rate) and you not only have the greater potential for contamination from conventional beef production to begin with, but the increase in antimicrobial resistant strains of E.coli – the strains more likely to result in the death of humans infected by it.
    It’s why more and more hospitals are taking conventionally processed antibiotic-dosed beef off their menus.
    The processing of any meat product includes potential risks of fecal contamination. However, the modern industrial approach to meat processing compounds that risk considerably. And that should be more than obvious, shoddy studies not withstanding.