Bacillus-Based Pet Probiotics: Stability and Formulation Considerations

2026-09-10 16:14:34

In the pet probiotic business, as long as the product contains live bacteria, there is a core contradiction that cannot be avoided: The bacteria must survive to reach the intestines and also have to survive during the Production Process and maintain their population without decline during the Shelf Life. This contradiction is particularly acute in extruded feed - high temperatures, high pressure, and high shear forces, which ordinary lactobacilli simply cannot withstand. The spore-forming bacteria have become the choice of more and more brands because, fundamentally, they solve an engineering problem, not just a Formulation issue.

1. Manufacturing Stability: Spores are "armor", but armor has weaknesses

The core advantage of spore-forming bacteria lies in their ability to form spores. In spore form, the bacterial metabolism almost comes to a standstill, and they have extremely strong tolerance to heat, acid, and dryness. This is why in extruded feed, the coagulans spore-forming bacteria (Bacillus coagulans) become one of the few Probiotics that can "survive until they leave the factory".

However, "resistance to heat" does not mean "invincible". A study on the extrusion process of coagulans spore-forming bacteria (GBI-30, 6086) showed that: Under low mechanical energy conditions (wetness of the barrel 35%, screw rotation speed 400 rpm), the loss of live bacteria is only 0.44 log; while in high shear conditions, the loss can reach more than 2.67 log. That is to say, the mechanical shear force during the extrusion process is often more lethal than just high temperature.

This provides a clear and direct lesson for the brand: If you choose to apply the additive after the expansion process, the survival rate of the spores will be more guaranteed; if you want to mix it in before the expansion, you must confirm the specific process parameters with the contract manufacturer - screw rotation speed, moisture content, and die pressure. These will directly affect the number of viable bacteria in the final product.

In addition, although the spores of Bacillus subtilis can withstand a temperature of 90°C, they are relatively sensitive to sudden changes in pressure. This requires special attention in the extrusion process. The tolerance of different spore strains varies, and it cannot be generalized. 

2. Strain Identification: Stating "Species" is Not Sufficient

On pet probiotic labels, one often comes across such notations as "spore-forming bacteria" or "Bacillus sp". From a regulatory perspective, this might be marginally compliant; from a branding standpoint, it is a waste of the most valuable asset. 

The specificity of the strain determines the specificity of the function. For example, for the Clostridium butyricum strain, GBI-30 and 6086, there are a large number of clinical studies supporting their effects on intestinal health and immune regulation. However, for other unidentified Clostridium butyricum strains, there may not be the same level of data backing. Consumers may not understand the difference between "strain" and "genus", but regulatory authorities and channel purchasers will take note. 

Domestic regulations are also moving in this direction. The GB 7300.505-2025 "Feed Additives - Bacillus licheniformis" released in 2025 clearly requires the labeling to include information about the strain, and it will be implemented on July 1, 2026. The newly approved Beles Bacillus licheniformis (CGMCC 24752) by the Ministry of Agriculture and Rural Affairs is also registered using the specific strain number. The trend is clear: strain identification is shifting from an "optional feature" to a "mandatory requirement".Practical operation suggestion: The label should at least indicate the level of "strain + strain number", such as "Streptococcus faecalis GBI-30, 6086" or "Bacillus subtilis C-3102". If multiple spore strains are used, list them one by one, do not simply write "spore bacteria complex".

3. Combinatorial Logic: Not All Bacteria Can Be Friends

The combination of spore-forming bacteria and lactic acid bacteria is the most common in pet probiotic products. Logically, it makes sense: spore-forming bacteria consume oxygen and create an anaerobic environment, while lactic acid bacteria are responsible for acid production and inhibiting harmful bacteria. However, in practical operation, the cultivation conditions and survival requirements of the two are very different. Improper combination will actually hinder each other.

A study on the co-culture of Bacillus subtilis and Lactobacillus plantarum found that when cultured in a 5:1 ratio, the combined growth effect of the two was the best, with the spore formation rate of Bacillus subtilis reaching 91.14%. The study also discovered that the acidic environment produced by Lactobacillus plantarum could promote spore formation, while the metabolites of Bacillus spores could alleviate the damage caused by oxygen to lactobacilli - this is a mutually beneficial relationship, but it is premised on the m atching of the ratio and the process. 

The lesson for the brand is: Recombinant formulation is not as simple as just adding several types of bacteria. If the contract manufacturer merely physically mixes several types of bacterial powders without considering their interactions during the shelf life, one type of bacteria might suppress another. It is recommended to require the contract manufacturer to provide data on accelerated stability tests before finalizing the formula, to confirm that the viable bacterial count of each type remains within the acceptable range by the end of the shelf life.

4. Labeling Considerations: Avoid These Pitfalls

First, the viable bacterial count should be labeled as "guaranteed value," not "added value." Many products indicate the amount added during production, but the decay during the shelf life can be considerable. Although Bacillus spores are stable, the carrier, Packaging, and storage conditions all affect the final viable bacterial count. The label should indicate the guaranteed viable bacterial count at the end of the shelf life. which is the responsible approach for consumers.

Second, efficacy claims should stay within the "support" boundary. Claims such as "support digestive health" and "maintain intestinal flora balance" are allowed, but claims like "treat diarrhea" and "relieve loose stools" cross into the territory of pharmaceutical claims. The FDA and AAFCO have clear distinctions, and crossing the boundary may trigger regulatory reviews.

Third, do not ignore the applicable range of strains. The applicable range of Beles Bacillus spores (CGMCC 24752) is for broiler chickens, and the national standard for Clostridium pasteuri is for feed additives. The regulatory framework for pet food and livestock feed is different, and when citing research data, be aware of whether the applicable range matches.

In summary: Bacillus spores have brought a real shelf-life advantage to Pet Probiotics, but this advantage can only be realized with the cooperation of formula design and label marking. Choose strains with strain numbers and research data, confirm the impact of process parameters on viable bacteria counts with the contract factory, and honestly label the guaranteed values on the label - these actions may seem like details, but they are precisely the foundation for brands to build product trust.