Microflora and the Gastrointestinal Tract

The gastrointestinal tract (GIT) of all healthy mammals contains approximately 400 species of microflora or microorganisms, including bacteria, yeasts, fungi and protozoa.  These microorganisms are acquired at birth from the mother, and later from the environment, and are necessary for the health and proper functioning of the GIT.

The microflora plays an intrinsic role in both digestion and immunology.  They help degrade food, especially in sick animals when enzymes may not secreted, convert waste material to energy, and are the first line of defense against infection.  Digestion in mammals is a cooperative effort between enzymes secreted by the body and endogenous microflora.  Some animals do not generate the required enzymes, as in those with exocrine pancreatic insufficiency (EPI), or lactose Intolerance (LI).  In these animals, the undigested material must then be degraded by microorganisms in the gut.

Because conditions in the GIT are not normal for animals with EPI and LI, they can cause the proliferation of microorganisms that are usually found only in small numbers.  These opportunistic pathogens can cause serious problems such as diarrhea and gas, if not controlled.

The endogenous microflora also play a key role in an animal’s immunological response.  Infections that enter through the GIT must first overpower the resident microflora, under normal healthy conditions this happens only with a very large initial dose of infectious microorganisms.  However, if the animal is stressed, a smaller number can successfully infiltrate the GIT.

Stress and the Gastrointestinal Tract

When a mammal experiences stress, changes in pH or the cessation of the nutrient flow can occur, killing protective microorganisms in the body.  When this happens, gaps appear in the natural protective barrier formed by these microorganisms.  Pathogens continually pass through the GIT, but if the animal is healthy and/or the pathogen number is low, they will pass through without doing any real damage.  Gaps in the protective barrier, however, allow pathogens opportunities to establish themselves.  Pathogens can make animals sick by simply competing for available nutrients and starving the beneficial microorganisms, or, more seriously, through the production of toxins.  Many forms of food poisoning involve bacterial toxins.  Sometimes a very small amount of toxin can cause an animal to become very sick or even die, and this process can occur quite quickly.


The conventional treatment of infection is to use antibiotics, which are like nuclear bombs to bacteria – they kill both good and bad indiscriminately.  That means along with the pathogens, many beneficial microorganisms may be killed as well, and sometimes the target microorganisms may even survive while beneficial ones are killed.  The original antibiotics were actually derived from microorganisms by isolating various strains of beneficial bacteria.  Beneficial microorganisms pack an assortment of biological weapons, both physical and chemical.

Unfortunately, microorganisms possess the capacity to evolve resistance, so antibiotics can become ineffective, pharmaceutical companies must continually search for new antibiotics.  Probiotics are microorganisms used to combat other microorganisms, and can provide an alternative to antibiotics that rapidly become obsolete.

Probiotics are defined as live microbial feed supplements which beneficially affect the host animal by improving its microbial balance.  Probiotic microorganisms, which include bacteria, yeasts, and fungi, are good competitors and can push back pathogens and allow the endogenous beneficial microorganisms to recover.  They also stimulate the immune system so that the body can fight more effectively.  Although probiotic microorganisms are confined to the GIT, they have wide-reaching effects and can help control infections not located in the GIT by activation of the immune system.

One way to think of probiotic microorganisms, which are generally not endogenous species unless isolated and developed for a particular species, is as armed placeholders.  They fill gaps until the endogenous microflora, decimated by antibiotics and/or stress, can recover.  Once they are back on their feet, they give the probiotics the boot.  Probiotic microorganisms usually do not attach and become permanent residents.

Because the GIT microflora is so varied (bacteria, yeasts, fungi and protozoa), it may require different types of microorganisms to fill different gaps in the GIT ecology.  Different species of all types are vulnerable in differing degree to stress and antibiotics.  The best way to insure that the greatest number of gaps are temporarily filled by probiotic microorganisms rather than opportunistic pathogens is to use a wide-spectrum probiotic, or one that contains the widest possible selection of different species in the required amounts.  No one probiotic species is the best in all possible scenarios.  All forms of Natur’s Pet Probiotics contain similar microorganisms, just in varying amounts depending on need.

Numbers of viable probiotic microorganisms are crucial, both the numbers of any one species (called colony forming units, or CFU) and numbers of different species.  The numbers of beneficial microorganisms must be superior to the invading organisms, even after they have passed the stomach.  Scientific literature recommends at least 108 (100,000,000) CFU/g or greater for treating sick animals.  The state of the animal and the intensity of the stress experienced dictates the concentration of the probiotic the animal should receive.

Probiotic microorganisms can be freeze-dried to retain full viability and potency until mixed with water, which happens naturally once ingested.  Some strains of bacteria are able to go dormant if availability of nutrients and/or environmental conditions becomes unfavorable for growth.  Powdered or granulated forms must be kept dry until fed to maintain full effectiveness.  Other conditions such as heat and sunlight can also kill probiotic microorganisms, even in the dry state.  For the longest shelf life for any probiotic, keep tightly sealed and refrigerated.  Dried forms may also be frozen once, but not repeatedly thawed and refrozen.  Freezing can extend full potency past the expiration date.  Paste and liquid probiotics must be refrigerated, and cannot be frozen.  They have a similar shelf life if kept sealed and refrigerated.  Probiotics come in at least three different concentrations:

1)  Maintenance – should be fed daily for everyday stresses such as weather and occasionally being left alone.  Usually supplied as a powder or granules.

2)  Intermediate  – should also be fed daily for chronic stresses and some digestive problems..  Usually supplied as a powder.

3)  Concentrated – can be fed one or more times daily for treatment of a sick animal until the animal is eating normally.  Available in either paste or liquid.

Because maintenance probiotics help re-establish proper microbial balance in the GIT, it can take from 10 to 14 days to become fully active.  The more concentrated forms start to work within just a few hours.  Probiotics are safe to give even at very high doses – they cannot be overdosed.

One common concern about probiotics is whether they survive past the stomach.  One of the most effective probiotic microorganisms is Lactobacillus acidophilus, a Lactic Acid-producing bacteria that actually lives in the stomach.  It prefers acid (the name means ‘acid-lover’) and will secrete enough acid on its own to maintain a pH uncomfortable for many opportunistic pathogens.  Research has shown that L. acidophilus generates enough acid during nursing to postpone the secretion of hydrochloric acid in the young mammal.

Other probiotic microorganisms prefer the less-acidic environs of the large intestine, and will successfully pass through the stomach and continue to the colon.  There are always some probiotic microorganisms that succumb to the extreme conditions in the stomach, that is why the initial dose needs to be as high as it does.  This will insure that the proper number of viable microorganisms reaches their target organs.  Some probiotic products boast about special encapsulation or other methods that are purported to by-pass the stomach.  These elaborate marketing schemes are not necessary as long as the product delivers the minimum CFU of viable probiotic microorganisms.

Handling and storage of probiotics can greatly influence the actual numbers of viable microorganisms that are fed to your pet.  If you buy off the shelf or from a distributor, do you really know what you are getting?  That package may indeed have had the CFU of the various organisms listed on the label when it left the manufacturer, but that does not mean it has that many when you actually make the purchase.  The most effective probiotics are the freshest ones, and the ones that have spent the least time away from the manufacturer.

Illness and the Gastrointestinal Tract

When an animal becomes ill, the GIT is shut down and energy and other nutrients are shunted to the immune system.  Normally, there is only about a day’s worth of ready energy stored in the muscles (as glycogen, or animal sugar), and when this runs out the metabolism must convert to burning fat.  Depending on the severity or the illness, the animal may not be able to complete the latter process.  As soon as the GIT tract shuts down, the clock starts ticking, and if the immune system cannot defeat the infection before energy runs out, the animal will die.

Probiotic microorganisms can metabolize food left on the GIT after it shuts down.  The energy derived from this metabolism, mainly volatile fatty acids (VFA), is readily absorbed by the lining of the digestive tract, thus buying the animal more time.

A serious complication of undigested food in the GIT after it shuts down is the arrival of highly fermentable nutrients in the large intestine.  This happens when sugars and starches that would normally have been digested enzymatically are fermented in the large intestine.  Pathogenic bacteria may proliferate and cause diarrhea, which in itself can be fatal.

Antibiotics may or may not kill the initial invading microorganisms, and they also kill beneficial protective microorganisms and can bring about secondary infections.  Probiotics are strongly recommended for use along with antibiotics, and at twice the usual rate.  Antibiotics can kill probiotic microorganisms, so the doses should be staggered to maximize the benefits.  Probiotics can prevent secondary infections and may help the animal recover faster.

Any conditions that result in a change in nutrient flow or pH can impact the viability of the endogenous microflora.  Many of these microorganisms are attached to the walls of the GIT, nutrients come to them, and when they don’t, or the pH in their niche changes even a tenth of a point, they can die.  Changes in non-GIT organs can impact this nutrient flow and may exacerbate the initial insult.  The digestive tract, the microflora, and the immune system are all intrinsically connected, what hurts one is going to impact the others.  Very few diseases are isolated in nature, they have repercussions throughout the animal body. 

Probiotics should be selected based on the health and stress level of the animal, and they work well with any veterinary therapy.  Both cats and dogs benefit from the regular use of probiotics.

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The statements above have not been evaluated by the Food and Drug Administration.  This product(s) is not intended to diagnose, treat, cure, or prevent any disease.

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