Certain plants and spices have been used as medicines by cultures across the world throughout history. In the face of growing global fears of antibiotic-resistant bacteria and ever-increasing bans on antibiotic use internationally, many groups are looking for antibiotic alternatives for growth promotion in old places, albeit with a high-tech twist.
Bavaria Corp. International, an EU-focused company that makes food safety products, is one such group. Bavaria Corp. has been looking to members of the allium family—a group including garlic and onions—which have long been known to have antimicrobial properties.
“The compounds with antimicrobial activity in these plants are organosulphured molecules,” explained the company in literature about its recently-announced feed additive product GOL. GOL uses extracts from garlic and leeks to improve weight gain and health in livestock by controlling harmful bacteria.
Nothing new under the sun
WLJ talked to a Bavaria Corp.’s Technical Director—a nutritional agronomist whose name was asked to be withheld for proprietary reasons—about how something like garlic extract can be an alternate to antibiotics.
The director pointed out that members of the allium family have been around and fighting bacteria for several million years.
“If these molecules didn’t work in the last 4 million years of evolution, we’re sure the garlic wouldn’t present it today,” he told WLJ.
The specific molecules of interest are a type of organosulphured molecules called propyl thiosulfinate oxide, or PTSO. PTSO can interfere with how proteins work with cell walls of bacteria. At the proper doses, PTSO can kill bacteria by effectively destroying their cell walls. Certain types of bacteria, specifically harmful gram-negative bacteria like Salmonella, E. coli, and Campylobacter, are especially susceptible to this effect.
Killing or controlling the populations of harmful bacteria in livestock can have two direct benefits. Some strains of Salmonella, E. coli, and Campylobacter can result in diseases in the host animal. Additionally, their presence in the animal can put consumers at risk if the meat is contaminated during processing.
Killing or keeping harmful bacteria in check can also help indirectly by giving the beneficial bacteria in the rumen less competition. Many of the beneficial microorganisms in the bovine digestive tract are gram-positive bacteria. Lactobacillus, which helps cattle convert carbohydrates in grains into usable compounds, and bifidobacteria are both examples of beneficial gram-positive bacteria.
While PTSO can also kill gram-positive bacteria, dosages must be much higher. At lower dosages, like those that might be used for growth promotion purposes, the harmful gram-negative bacteria are attacked while leaving the less susceptible gram-positive bacteria alone.
“It is very important to note that this is like in any other issue in life; these molecules are good, but if you overdose, they can kill the animal,” Bavaria Corp.’s Technical Director told WLJ. “Nothing is good or bad. Nothing is poison or treatment, just the doses.”
Allium efficacy
Even though allium plants have been used for their antimicrobial properties for centuries, allium-derived feed additives for livestock are relatively new and untested. This is especially true for cattle and in the U.S., and compared to antibiotics. Most of the research into allium derivatives as an alternative to antibiotics for growth promotion has occurred in swine and poultry, and in other countries.
A July 2017 report from the Pew Charitable Trusts on antibiotic alternatives noted that the effect of “phytochemicals”—plant-derived compounds such as extracts and essential oils that have antimicrobial properties—for growth promotion in cattle is poorly studied and poorly understood.
“In adult cattle, a recent meta-analysis concluded that the available data are insufficient to reach a final determination regarding efficacy as growth promoters,” the report pointed out.
“Some studies suggest efficacy of phytochemicals for the prevention of diseases in cattle such as diarrhea and to improve digestive health, but more studies are clearly needed.”
Several international studies in swine and poultry have found that allium-derived products—ranging from chopped fresh onion to essential oil from garlic—have encouraged weight gain in test animals in feed trials. One broiler chick feeding study speculated the observed weight gain was the result of how the organosulfured compounds found in onions can prevent the feeling of fullness, resulting in continued eating.
There have been mixed results in these studies however. Many studies note that the mechanism of efficacy, if efficacy was observed, is not understood well. The Pew Charitable Trust report additionally pointed out that most studies are based on lab experiments that do not accurately reflect commercial livestock operations.
Resistance reimagined
Fear of antibiotic resistance is driving efforts to find antibiotic alternatives like those derived from allium plants. Other alternatives are being explored. More on these can be found in the story on the cover of this week’s issue of WLJ.
However, bacteria are living organisms that evolve quickly to adapt to threats. Bacteria and other microorganisms could eventually adapt to the antibiotic alternatives as well. Bavaria Corp.’s Technical Director told WLJ that resistance and adaptation is part of nature. But—after explaining how wild ruminants sometimes appear to self-medicate by consuming allium plants—he added that keeping nature in mind can help us adapt as well.
“We are trying to use an approach more closely related to the evolution of the animals we are growing for producing meat,” he said.
“The philosophy is not to treat animals; it is to avoid them getting sick. … This philosophy is easier because we are not looking to treat animals; we are trying to give those animals the tools for preserving their own homeostasis—their health status.” — Kerry Halladay, WLJ editor
