Why CFU Counts Are More Relevant to Simple Microbial Products Than Complex Consortia

Colony-forming unit (CFU) counts remain the standard method for quantifying viable microbes in many commercial products. However, their relevance and reliability differ markedly between simple, single-strain (or few-strain) products and complex, multi-genus microbial consortia intended for animal use.

CFU: What It Actually Measures

CFU quantifies the number of viable cells capable of forming visible colonies under specific laboratory plating conditions (media type, temperature, oxygen level, incubation time). It is a useful proxy for “live and culturable” cells at the moment of testing.

For simple products - single-genus probiotics or products containing only a few closely related, easily cultured genera (for example a Bacillus spore preparation or a single Lactobacillus culture) CFU works well because:

The organisms have similar growth requirements.
They form colonies reliably on standard media.
The count closely reflects the number of cells expected to remain viable and active after oral administration to animals.
Regulatory frameworks and quality-control systems are built around this metric for such products.
In these cases, a declared minimum CFU per dose or per gram provides a meaningful indicator of product strength and consistency for animal application.

Limitations of CFU for Complex Multi-Genus Consortia

Complex products containing multiple genera (including Lactobacillus, Rhodopseudomonas, Saccharomyces and associated beneficial microbes) present fundamental challenges when used as animal probiotics:

Diverse growth requirements - Different genera require different oxygen levels (strictly anaerobic versus micro-aerobic versus facultative), pH optima, and nutrient sources. A single plating method cannot accurately recover all members of the consortium.
Differential culturability - Many functionally important genera form colonies poorly or not at all on conventional media. CFU therefore systematically under-represents the true viable population that will interact with the animal’s gastrointestinal tract.
Metabolite contribution - Efficacy often depends as much on the organic acids, enzymes, and other beneficial compounds already present in the product as on the living cells themselves. CFU ignores this non-cellular activity.
Population dynamics after administration - Once consumed by the animal, the consortium interacts with the existing gut environment, and relative abundances shift rapidly. The original bottle CFU becomes a poor predictor of the active population inside the animal.
In short, a single CFU number for a complex multi-genus consortium is an incomplete and potentially misleading snapshot of what the animal actually receives.

Dosage and Efficacy Matter More Than a Single CFU Figure

For complex consortia used in animals, practical performance is determined by:

Field-validated dosing rates rather than theoretical cell counts. Application rates (millilitres per animal or per kilogram of body weight) have been established through repeated observation of animal response, feed intake, gut stability, and overall resilience.
Functional activity - Support of a favourable gastrointestinal microflora, competitive exclusion of undesirable organisms, and production of beneficial metabolites are more relevant endpoints than colony counts.
Consistency of biological effect under real-world conditions (diet, stress, age, and existing gut status of the animals) rather than laboratory recovery rates.
Ability of the community to establish and function inside the animal. The critical quality factors become the overall health of the inoculum and the conditions under which it is delivered, not a laboratory CFU value alone.
This approach aligns with how complex multi-genus microbial products for animals are evaluated: by measurable outcomes in livestock performance and gastrointestinal balance rather than by a single culturable-cell number.

Practical Implication

When evaluating or applying a simple single-genus product for animals, CFU remains a useful and appropriate quality metric. When working with a multi-genus consortium, the more scientifically robust indicators are the validated dosing rates, the observed animal response, and the functional characteristics of the product. Relying solely on CFU in the latter case risks underestimating both the living diversity present and the contribution of the metabolite fraction that drives much of the observed benefit in the animal.

EquineCare Probiotic is a 100% natural topical probiotic spray designed to support your horse’s skin health. It works by repopulating the skin with beneficial microbes that naturally crowd out harmful bacteria and fungi—supporting the skin’s natural defences without harsh chemicals. Made here in NZ.

While we can’t make health claims, some customers choose to use EquineCare Gut Prebiotic and Probiotic as part of their approach to supporting gastric comfort. It contains no added sugars or fillers and is suitable for horses on ulcer-sensitive diets. As always, consult your vet if your horse is showing signs of gastric discomfort.

Simply pour the recommended amount over your horse’s feed once daily. The liquid formula is palatable and easy to mix. It’s suitable for horses of all ages, including foals and seniors. Dosage information is provided on the bottle.

Mud fever (also called pastern dermatitis) often appears as scabs, redness, and hair loss on the lower legs. EquineCare Probiotic Spray helps by outcompeting harmful bacteria and supporting healthy skin recovery—without the need for scab picking or harsh chemicals. Spray daily until the skin improves.

Rain scald (also known as rain rot) is a bacterial skin condition caused by prolonged wetness. It often appears as matted clumps of hair, scabs, or bare patches, especially over the back and rump. To treat rain scald naturally, spray the affected area once or twice daily with EquineCare Probiotic. The beneficial microbes help restore skin balance and reduce irritation.

To help prevent rain scald, keep your horse as dry as possible in wet conditions and apply EquineCare Probiotic Spray once or twice weekly or after rain. Regular use supports the skin’s microbiome, helping to protect against bacterial overgrowth in damp environments.

Yes. EquineCare Probiotic Spray can be used on hooves to treat thrush and early stage seedy toe. Spray directly into the frog and along the white line 1–2 times a day. The spray helps outcompete pathogens that thrive in moist, anaerobic conditions.

Spray directly onto the affected area once or twice daily. There’s no need to rinse or wipe off. For preventative use, apply 1–2 times a week, especially in wet or muddy conditions.