Feedstuffs ReprintFeedstuffs, May 9, 2016

© 2015 Feedstuffs. Reprinted with permission from Vol. 88, No. 05, May 9, 2016

By JANE M. CALDWELL*

THANKS to television ads for yogurt beginning in the 1970s, it’s com-mon knowledge that a probiotic is

a live bacterium found in fermented milk that, when eaten, confers health benefi ts to the host (Fuller, 1989). The take-home message: Yogurt improves gut health and overall wellness due to benefi cial bacteria such as lactobacillus in the culture.

Next, nutritionists discovered the use-fulness of prebiotics — dietary fi ber that nourishes probiotics and helps them grow in the gut (Gibson and Roberfroid, 1995). “Synbiotic” is a term that describes the useful collaboration between the probi-otic and the prebiotic — the synergy be-tween benefi cial bacteria and fermentable fi ber.

Previously, “abiotic” was defi ned as “non-living chemical and physical parts of the environment that affect living organ-isms.” Beginning in the late 20th century, academic researchers in microbiology and public health recognized and report-ed that non-viable bacteria and their fer-mentates could also confer health benefi ts to the host when consumed.

In peer-reviewed literature, abiotic was redefi ned as “non-viable probiotic organ-isms or cellular components ... (that) may be effi cacious in specifi c situations” (Shortt, 1999), that “mediate a physiologic benefi t” (Reid et al., 2003) and that “exert benefi cial effects on health or well-being” (Klaenhammer, 2007).

The new academic defi nition of abiotic is: non-viable bacteria and their fermen-tates that confer health benefi ts to the host.

Immunity in livestockThe scientifi c literature has documented that many probiotic benefi ts from viable cells can also be obtained from popula-

tions of dead, or abiotic, bacteria (Adams, 2010). Abiotic bacteria, when ingested, can have signifi cant effects on animal im-munity. This is due to their cell wall com-ponents stimulating monitoring systems in the gut, serving as an adjuvant to in-crease the hosts’ immune response to for-eign particles or antigens.

Gram-positive bacteria, such as lacto-bacillus (pictured), have a thick cell wall composed of peptidoglycan. Peptidogly-can — a polymer made up of sugars and amino acids — makes up 90% of the dry weight of lactobacillus (Hogan, 2010). When abiotics are consumed, the pep-tidoglycans from the dead cells trigger the surveillance system in the gut, which turns on several immune responses.

The immune system relies on a cascade of different molecules. Like a line of domi-noes, each molecule relies on a push from an adjacent molecule before it can perform its duty. Feeding abiotics to a healthy ani-

mal keeps the immune system in a mildly stimulated state, which keeps the cascade system functional. Because of the peptido-glycans in the feed, the immunity cascade is already operational and ready for any stress or challenge that may arise during livestock production or transportation.

Other abiotic cell wall components shown to stimulate host immunity include beta-glucans, teichoic and lipoteichoic ac-ids, lipopolysaccharides and other unde-fi ned “cell homogenates” (Adams, 2010).

Other adjuvant properties of abiotics in-clude their bacterial DNA, known as CpG motifs. When viable or non-viable bacte-ria cells are lysed by acids in the upper gastrointestinal tract, bacterial DNA is released into the host’s gut. Bacteria have DNA sequences that are different from the host’s own DNA. Once again, like the bacterial peptidoglycan layer, the surveil-lance system recognizes these non-host DNA sequences as a foreign antigen and upregulates the immune response. Lac-tobacillus species carry high concentra-tions of CpG motif DNA, which stimulates epithelial and immune cells in the host’s intestine (Kant et al., 2014).

Both the cell wall components and bac-terial DNA are available to the host im-mune signaling systems, no matter wheth-

Abiotics, their fermentates have advantages for host

*Dr. Jane M. Caldwell is director of research and development for TransAgra Interna-tional.

Abiotics are alternatives to antibiotics due to their ability to upregulate the immune system, inhibit infections, promote

healthy gut microflora and reduce stress in the host.

Reprint2 Feedstuffs, May 9, 2016

er the ingested bacteria are alive or dead, probiotic or abiotic.

Abiotic metabolitesAn abiotic differs from a probiotic bacte-rium in that it is rendered non-viable af-ter fermentation by heat, acidifi cation or some other stabilization process. During fermentation, abiotic metabolites are pro-duced and released when bacteria break down the substrate they are fed. If the fer-mentation uses milk or milk proteins as a substrate, proteolysis by certain probiotic bacteria can produce bioactive peptides.

Bioactive peptides are short sequences of amino acids that perform non-nutritive functions in the host. These nutraceutical peptides include angiotensin I-converting enzyme inhibitors, which dilate blood vessels, exert a hypotensive effect, lower blood pressure and reduce stress in the host (Meisel, 2005; Clare and Swaisgood, 2000).

Bioactive milk peptides increase absorp-tion of minerals — especially calcium — in the gut (Meisel, 2005). They also have an-tioxidant activities, function to stimulate the host immune system, inhibit cancer cell growth (Clare and Swaisgood, 2000) and have antimicrobial properties derived from the whey protein lactoferrin (Meisel, 2005). Other health-promoting abiotic metabolites produced include B vitamins (Vinderola, 2008).

Advantages over probioticsAbiotics, while using some similar modes of action in the host, have several advan-tages over probiotics.

Ease of use and longevity. An abiotic does not contain live bacteria, so it does not require refrigeration or a cold chain during shipment. It has a longer shelf life at any temperature. Chemicals, medica-tions in feed or physical processes that kill live bacteria do not reduce the effi cacy of an abiotic. Therefore, abiotics can be successfully incorporated into total mixed rations that have been heat processed or extruded.

Researchers have reported fi nding vi-able probiotic bacteria (Bifi dobacterium spp.) in high quantities in the host’s gut while the bacteria were constantly con-sumed, but these were no longer detect-able eight days after consumption ceased (Bouhnik et al., 1992). They concluded that outside sources of probiotics would not permanently colonize the host colon.

Non-specifi c hosts. An abiotic enhanc-es the growth of the naturally occurring, benefi cial bacteria already present in the host gut. Many benefi cial gut bacteria are fastidious organisms that require an en-vironment fi lled with nutritional building blocks such as amino acids, sugars and vitamins. They are totally dependent on the host organism for nutrients. Due to evolutionary genome shrinkage, they lost

the genes needed for nutrient synthesis. Instead, they developed rapid, multiple transport systems.

The fastidious benefi cial bacteria are able to outcompete pathogens introduced from outside the gut by having superior cellular transport systems that can quick-ly move these nutrients from the outside to the inside of the cell, where they are consumed. An abiotic provides lunch for the native benefi cial bacteria in the form of cellular components rich in amino ac-ids, energy and metabolites such as B vi-tamins.

Since an abiotic feeds the host’s native benefi cial microbes, it is not species spe-cifi c and can benefi t many different animal hosts, including ruminants, monogastrics, avian or hind-gut fermenters.

Probiotic bacteria are adapted to a par-ticular host species; there is little cross-attachment to other species. With a few exceptions, lactobacillus isolates adhere to the cells of the animal from which they were obtained (Lin and Savage, 1984; Sav-age, 1984). Even if a probiotic can attach to the gut of a host, that does not guaran-tee colonization or proliferation (Savage, 1984; Sellwood, 1984).

Probiotics are grown in fermentation vessels made of steel or glass. They can adapt to growth in this manmade environ-ment and lose their ability to thrive in the gut of the host. After many generations of growth in artifi cial culture media, bac-terial cell surfaces diverge from those of strains grown in the host (Savage, 1984).

Similar modes of action. Both probi-otics and abiotics have been found to shorten the effects of or eliminate viral infection and inhibit colonization of the gut by disease-causing bacteria such as pathogenic Escherichia coli strains. Abiot-ics or cell-free extracts of lactobacillus fer-mentations have reduced the duration of rotavirus diarrhea (Salminen et al., 1999), protected mice against infl uenza virus infection (Hori et al., 2001), reduced vis-ceral pain (Kamiya et al., 2006), enhanced immune response to pneumococcal in-fection in malnourished mice (Villena et al., 2009), suppressed E. coli counts in artifi cially reared piglets (Pollmann et al., 1982), inhibited E. coli adhesion in the pig-let gut (Blomberg et al., 1993) and reduced scours while increasing the digestion of crude fi ber in growing/fi nishing pigs (Hale and Newton, 1979).

In aquatic species, non-viable lacto-bacilli were not found to be effective in improving growth parameters but signifi -cantly improved immunity and disease resistance in freshwater prawns (Dash et al., 2015).

Probiotics and abiotics both must be ca-pable of being prepared on an industrial scale. Both must be able to pass through the high-acid environment of the upper gastrointestinal tract of the host to reach the colon. However, the probiotic’s modes of action are dependent on viable organ-isms attaching to the host gut. An abiotic

dose is more dependable since it cannot be killed by acid or bile salts.

The cell wall components and CpG mo-tif DNA are contained in the non-viable husk of the abiotic and are less affected by chemical or enzymatic assaults than the viable bacteria are. These cell compo-nents do not depend on viability to work. Many bioactive peptides are produced by hydrolysis or cleavage of abiotic metabo-lites from milk fermentations in the acidic host gut (Clare and Swaisgood, 2000).

One might argue that many probiot-ics become abiotic due to low stability or chemical death. It is the burden of the probiotic manufacturer to prove abiotic modes of action with the product.

Safety issues. Probiotics are living bac-teria. Living organisms are dynamic — constantly changing and evolving for the sake of survival. To this end, probiotics can exchange DNA with other bacteria, including pathogenic bacteria or those with antibiotic-resistance genes. This can cause probiotic bacteria to acquire toxin genes or antibiotic resistance. While these are rare events, mutations by genetic transfers are noted risk factors when feed-ing probiotics (Salminen et al., 1999).

Animals that are immune-compromised due to either young or advanced age, preg-nancy or disease can be infected by any viable microbe. When an infection occurs with a normally non-pathogenic microbe, this is termed an opportunistic infection.

Abiotics are non-viable and cannot cause infection in weakened animals. Even though approved probiotics are consid-ered safe for use and the risk of infection is small, abiotics raise fewer safety con-cerns (Salminen et al., 1999).

Bio-containment. Lactobacilli have been identifi ed as one variety of bacteria that may provide health benefi ts when ingested. However, it is important to note that not all lactobacillus species have pro-biotic or abiotic capabilities. These claims cannot be made without rigorous test-ing to prove effi cacy with positive health results. Of course, research and testing are expensive. Once probiotic or abiotic strains are identifi ed and validated, they are closely guarded intellectual property.

Abiotics have another practical advan-tage over probiotics in that they cannot be cultured from the commercial product and pirated by unscrupulous parties.

One fi nal safety advantage: Abiotics, be-cause they are non-viable, cannot be ac-cidentally released into the environment, including homes, water supplies, fi elds, farms or sewage systems.BINDING. Abiotic lactobacilli were found to bind and remove afl atoxin B1 — a po-tent feed toxin — from contaminated me-dia (Bovo et al., 2014). Heat- or acid-killed bacteria were found to be more effective than live bacteria in binding afl atoxin (El-Nezami et al., 1998).

Helicobacter pylori, a bacterium that causes numerous gastrointestinal diseas-es, was bound and deactivated by abiotics

Reprint Feedstuffs, May 9, 2016 3

(Mehling and Bushajn, 2013). This aggre-gation was cited as a possible antibiotic-free therapy in human medicine (Holz et al., 2015).

Advantages over prebioticsPrebiotics are fi ber — starches like cellu-lose and inulin that are indigestible to the host but can feed the probiotic bacteria in the gut (Gibson and Roberfroid, 1995). Like abiotics, prebiotics are non-viable sources of nutrients for benefi cial gut bac-teria.

This is the major mode of action for prebiotics. They do not, by themselves, stimulate immunity, inhibit pathogens, bind toxins or reduce the effects of stress as abiotics do.

Abiotics feed the native benefi cial mi-crobes but offer more than energy in the form of inulin or cellulose. Abiotics also offer structural building blocks such as proteins and amino acids, enzymes need-ed for metabolic functions, vitamins and minerals — all in forms specifi c for bacte-rial transport and use.

SummaryProbiotics and abiotics are alternatives to antibiotics due to their ability to upregu-late the immune system, inhibit bacterial and viral infections, promote healthy gut microfl ora and reduce stress in the host.

Treated animals show signifi cant im-provement over controls when they are not reaching their full genetic potential due to environmental stressors such as suboptimal feeding or management, birth, weaning, transportation, lactation, heat, dehydration, changes in rations or any conditions that could disturb or inhibit ideal gut microfl ora.

However, abiotics offer many advantag-es over viable direct-fed microbials and fi ber supplementation, including:

• No refrigeration or cold chain ship-ment is required.

• They have greater stability and longer shelf life.

• They can withstand further processing such as heat and extrusion.

• They are not host specifi c.• They can bind toxins and pathogens.• They cannot mutate and acquire anti-

biotic resistance.• They cannot become opportunistic

pathogens.• They cannot be cultured by others

from the product line.• They cannot escape into the environ-

ment.• The dosage delivery is safe and de-

pendable.

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