Which Microorganisms Should We Use to Treat Gastrointestinal (GI) Stasis in Rabbits?

Which Microorganisms Should We Use to Treat Gastrointestinal (GI) Stasis in Rabbits?
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Owners often share their experiences in solving rabbit health issues by using various products recommended by veterinarians. It is time to truly understand the use of microorganisms (probiotics). Some choose products containing Lactobacillus, some use energy-rich gel tubes, and others add electrolytes like potassium and sodium. How appropriate are these? It depends on understanding and clinical judgment for each specific case—not every case is the same.

In Brief:
GI stasis caused by insufficient lignin and cellulose fiber often implies that the proportion of digestible fiber, carbohydrates, or other energy sources is excessive. This results in hindgut acidosis (pH < 6; in cattle, it may drop below 5.0 - 5.5). These acids are produced by lactic acid bacteria or carbohydrate-utilizing groups that convert sugars into lactic acid, such as Lactobacillus, Pediococcus, Streptococcus, and Bifidobacterium.

While Lactobacillus and Bifidobacterium are commonly discussed and used, the normal rabbit digestive tract contains very little to no Lactobacillus. Their numbers increase when the diet is high in carbohydrates but decrease when the environment becomes excessively acidic and unsuitable. Interestingly, these bacteria are found at their highest stable levels in high-fiber, low-energy diets. In the early stages of high-carbohydrate intake, they proliferate rapidly and produce massive amounts of lactic acid. This also triggers an increase in bacteria that utilize lactic acid to produce various volatile fatty acids (VFAs) or use acetic acid and ethanol through the same pathway.

The negative impact occurs with continuous carbohydrate feeding—a common mistake among owners who lack a proper understanding of nutrition or receive misinformation from social media. This leads to excessive lactic acid production in acute, sub-acute, and chronic forms. As acidity increases, beneficial microorganisms can no longer survive, allowing opportunistic pathogens to thrive, leading to a state of microbial imbalance known as dysbiosis.

The Use of Probiotics in High Lactic Acid Conditions
In states of high lactic acid, using Lactobacillus or any lactic acid bacteria (LAB) may not be beneficial. Even if they are supplemented, they may not survive or colonize. While some products use acid-resistant strains, if the owner continues to feed high-carbohydrate diets, these bacteria can accelerate lactic acid accumulation. This group produces lactic acid rapidly and risks stimulating higher histamine production from the subsequent fatty acids produced by LAB-related bacteria, further impacting health. (Note: Lactobacillus isn't just used in herbivores; it is also found in cat treats to aid starch digestion, though this requires an understanding of feline gastrointestinal physiology).

Impacts of Acidosis: Is Potassium Supplementation Necessary?
When excessive acidity occurs in the GI tract, the body attempts to buffer it by secreting bicarbonate from mucus glands (increasing mucus production) and transferring carbon dioxide into the bloodstream. This can lead to systemic acidosis and histaminosis, which affects potassium balance.

Potassium shifts out of cells during systemic acidosis. Some products attempt to supplement potassium, and some veterinarians use glucose to stimulate insulin secretion, hoping to drive potassium back into the cells. However, if the underlying acidosis—the cause of the cellular leakage—is not corrected, it can lead to false or pseudohyperkalemia initially. Eventually, as potassium is lost through the GI tract and urine, a total body deficit occurs, affecting GI motility and causing muscle weakness. While supplementation helps many cases, it must be done with caution and diagnostic monitoring, as blood levels do not always reflect total body stores.

Acute Treatment of GI Acidosis with Microorganisms: What Works?
To resolve GI acidosis caused by high carbohydrate intake, the focus should be on direct-fed microbials (probiotics) that are acid-resistant or hardy. Avoid products with added starch, sugar, or protein, as well as unnecessary electrolytes that could complicate the disease cycle. Initially, high-energy supplements should be withheld in favor of high-fiber or lignocellulose-rich diets to stimulate the fusus coli to return to normal function.

In acute and sub-acute acidosis where symptoms are severe, rapid reduction of GI acid is vital. Specific types of yeast (which are larger than bacteria) are preferred. These yeasts compete with Lactobacillus and other LAB for substrates. They utilize carbohydrates more efficiently but release lactic acid slowly, and some strains can even utilize existing lactic acid. This quickly reduces GI acidity, making the animal more comfortable.

However, if the root cause is not addressed, this is merely palliative. Recovery diets often include yeast to ensure continuous intake alongside high fiber (specifically ADF > 30%). This yeast also stimulates the recovery of protozoa, which consume lactic acid, further stabilizing the pH. Once the pH returns to the optimum range, other beneficial microbes will flourish. Some probiotic brands use a blend of microorganisms, using yeast as the primary agent combined with appropriate levels of Lactobacillus and Bacillus for immune modulation and pathogen inhibition.

Conclusion
This is a summarized overview. The role of microorganisms is vast. Interested parties should study further. We hope this information is useful for your clinical consideration.