SIGMA BIOVET SCIENCES
Animal Microbiome & Biotics Glossary
Key Terms in Microbiome Science, Probiotics, and Regulatory Strategy
A
AAFCO (Association of American Feed Control Officials)
A voluntary membership association of state, federal, and international regulatory officials responsible for safeguarding animal feed, including pet food and supplements. AAFCO sets ingredient definitions, labeling standards, and model regulations that most US states adopt. For probiotic and microbiome product companies, AAFCO compliance is not optional — it determines whether your product can legally sit on a retail shelf.
Dr. Nihan’s Note: The FDA-AAFCO MOU expired in October 2024. If you are still operating under the old assumptions, your product may already be non-compliant. This is one of the most misunderstood regulatory shifts in our industry right now.
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AFIC (Animal Food Ingredient Consultation)
The new FDA process (finalized January 2025) that replaced the old AAFCO ingredient review pathway for certain animal food ingredients, including some probiotic strains. AFIC requires companies to submit safety and efficacy data directly to FDA-CVM for evaluation. The process demands rigorous documentation, and incomplete submissions get returned without review.
Dr. Nihan’s Note: Many companies are still confused about whether their ingredient needs an AFIC submission or falls under a different pathway. Getting this wrong wastes months and thousands of dollars. If you are unsure, get expert guidance before you submit.
AMR (Antimicrobial Resistance)
The ability of bacteria, viruses, fungi, and parasites to survive and multiply despite exposure to antimicrobial drugs that previously killed them. AMR is recognized by WHO, FAO, and WOAH as one of the top global health threats. In animal health, responsible microbiome modulation through probiotics and biotics is increasingly studied as a strategy to reduce antibiotic use and support antimicrobial stewardship across the One Health framework.
Amplicon Sequencing
A targeted DNA sequencing method that amplifies and reads a specific genetic marker (most commonly the 16S rRNA gene in bacteria) to identify which microorganisms are present in a sample. It is cost-effective and widely used for microbiome profiling in animals but provides limited information about the functional capabilities of the microbial community compared to shotgun metagenomics.
Antimicrobial Stewardship
A coordinated set of strategies to optimize the use of antimicrobial agents in both human and veterinary medicine. The goal is to use antibiotics only when necessary, at the right dose, for the right duration, and with the right drug. In animal health, stewardship programs increasingly incorporate microbiome-based alternatives like probiotics to reduce unnecessary antibiotic prescriptions and slow the development of resistance.
B
Biomarker (Microbiome Biomarker)
A measurable biological indicator used to assess the state of an animal’s microbiome or its response to an intervention. Examples include microbial diversity indices, specific taxa abundance, short-chain fatty acid levels, and markers of gut barrier function. Biomarkers are critical for evaluating probiotic efficacy in clinical trials and for developing evidence-based health claims.
C
CFU (Colony Forming Units)
The standard unit of measurement for viable (living) bacteria in a probiotic product. CFU counts indicate how many bacteria in a sample are capable of multiplying. For animal probiotics, the CFU count that matters is the guaranteed amount at the end of shelf life, not at the time of manufacture. Many products list inflated manufacture-date counts that mean nothing by the time the product reaches the animal.
Dr. Nihan’s Note: If a product only lists CFU at manufacture but not at expiration, that is a red flag. Bacteria die during storage. The only number that matters is what is alive when your animal actually consumes it.
Colonization Resistance
The ability of a healthy, established gut microbiome to prevent the colonization of harmful (pathogenic) microorganisms. A diverse and stable microbiome competes with invaders for nutrients and attachment sites, produces antimicrobial substances, and stimulates the host immune system. When colonization resistance breaks down — through antibiotics, stress, or disease — animals become more susceptible to gut infections.
D
Dysbiosis
An imbalance or disruption in the composition and function of the gut microbiome. Dysbiosis in animals can be triggered by antibiotics, dietary changes, stress, illness, or environmental factors. It is associated with a range of conditions including diarrhea, inflammatory bowel disease, immune dysfunction, and increased susceptibility to infection. Restoring microbial balance through targeted biotics is one of the primary goals of microbiome-based veterinary interventions.
Dr. Nihan’s Note: Dysbiosis is easy to diagnose and hard to define precisely. Every lab and every study uses slightly different criteria. Be cautious of any product that claims to “fix dysbiosis” without specifying what they measured and how.
E
Eubiosis
The state of a balanced, healthy gut microbiome where beneficial microorganisms coexist in stable proportions and support the host’s digestion, immunity, and overall health. Eubiosis is the opposite of dysbiosis. Maintaining eubiosis in animals is the foundational goal of responsible probiotic and prebiotic interventions.
F
FDA-CVM (Center for Veterinary Medicine)
The division of the U.S. Food and Drug Administration responsible for regulating animal drugs, animal food (including pet food), and veterinary devices. FDA-CVM oversees the safety and efficacy of animal health products, including probiotic supplements and microbiome-based therapies. For companies developing animal biotics, understanding FDA-CVM’s regulatory expectations — especially around claims language and ingredient status — is essential to avoid warning letters and market access problems.
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G
GMP (Good Manufacturing Practice)
A set of regulations and quality standards that ensure products are consistently produced and controlled according to established safety and quality benchmarks. For animal probiotic manufacturers, GMP compliance covers facility design, raw material sourcing, production processes, batch testing, labeling, and storage conditions. A scientifically excellent probiotic strain can fail in the market if manufactured under poor GMP conditions.
GRAS (Generally Recognized as Safe)
A U.S. FDA designation indicating that a substance (including certain probiotic strains) is considered safe for its intended use based on a long history of common use in food or on published scientific evidence. GRAS status can simplify the regulatory pathway for animal probiotic ingredients, but it does not exempt a product from proper labeling and claims compliance.
Gut Barrier Function
The ability of the intestinal lining to serve as a selective barrier — allowing nutrients to pass into the bloodstream while blocking pathogens, toxins, and undigested particles. A healthy microbiome supports gut barrier integrity through the production of short-chain fatty acids, mucus layer maintenance, and immune modulation. When the gut barrier is compromised (“leaky gut”), inflammation and systemic health problems can follow.
Gut-Brain Axis
The bidirectional communication network between the gastrointestinal tract and the central nervous system. In animals, the gut microbiome influences brain function and behavior through neural, hormonal, and immune pathways. Research in companion animals has linked gut microbial composition to anxiety, stress responses, and cognitive function. This connection is one of the most active areas of veterinary microbiome research today.
Dr. Nihan’s Note: Did you know that more than 75% of serotonin — the happiness hormone — is made in the gut, not the brain? Same for your dog. The gut-brain axis is not a theory. It is measurable biology.
H
Host-Microbe Interaction
The dynamic relationship between an animal (the host) and the microorganisms living in and on its body. These interactions can be beneficial (probiotics aiding digestion), neutral (commensal bacteria), or harmful (pathogen colonization). Understanding host-microbe interactions at the molecular level is fundamental to designing effective probiotic and microbiome-based interventions for animal health.
M
Metagenomics
The study of genetic material recovered directly from environmental or biological samples (like gut contents or fecal samples) without the need to culture individual organisms. In veterinary microbiome research, metagenomics allows scientists to analyze the full complexity of an animal’s gut microbial community — who is there, what they can do, and how they interact — providing a far more complete picture than traditional culture methods.
Microbial Metabolites
Biochemical compounds produced by microorganisms during their metabolic activity. In the gut, key microbial metabolites include short-chain fatty acids (SCFAs), vitamins (B12, K), amino acids, and signaling molecules that influence host immunity, energy metabolism, and gut barrier function. Many of the health benefits attributed to probiotics are actually driven by the metabolites these organisms produce, not just by the bacteria themselves.
Microbiome
The entire ecosystem of microorganisms — including bacteria, fungi, viruses, and archaea — along with their genes and the surrounding environmental conditions, living in a specific habitat such as the gut, skin, or respiratory tract. In animals, the gut microbiome is the most studied and is recognized as essential for digestion, nutrient absorption, immune function, pathogen defense, and even behavior.
Dr. Nihan’s Note: People often use “microbiome” and “microbiota” interchangeably. Technically, the microbiome includes the organisms plus their genetic material and environment. The microbiota refers to the organisms themselves. In practice, both terms are used loosely, but precision matters when you are writing regulatory documents or scientific papers.
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Microbiota
The community of living microorganisms (bacteria, fungi, viruses, archaea) inhabiting a specific environment in or on the body. The gut microbiota of animals varies by species, age, diet, health status, and environment. Unlike “microbiome” (which includes genetic material and ecological conditions), “microbiota” refers specifically to the organisms themselves.
Minimum Inhibitory Concentration (MIC)
The lowest concentration of an antimicrobial agent that prevents visible growth of a specific bacterium in laboratory conditions. MIC testing is used to determine whether a probiotic strain carries antibiotic resistance genes and to evaluate the antimicrobial susceptibility of both target pathogens and probiotic candidates. MIC data is often required in regulatory dossiers for probiotic products, especially in the EU.
N
NASC (National Animal Supplement Council)
A U.S. industry organization that sets quality standards and compliance guidelines for animal health supplements, including probiotics. NASC membership and its Quality Seal program signal to retailers and consumers that a product meets specific quality, labeling, and adverse event reporting standards. NASC compliance is increasingly required by major pet retailers for shelf placement.
O
One Health
A collaborative, multisectoral approach that recognizes the health of people, animals, and the environment are interconnected. In the context of the microbiome and AMR, One Health emphasizes that antibiotic use in animals affects human resistance patterns and vice versa. Responsible microbiome modulation in veterinary medicine — reducing unnecessary antibiotics, supporting gut health through biotics — is a One Health strategy in action.
P
Paraprobiotic
Inactivated (non-viable) microbial cells that, when administered in adequate amounts, still confer health benefits to the host. Unlike probiotics, paraprobiotics do not need to be alive to work. They can offer improved stability, longer shelf life, and simplified safety profiles. The regulatory classification of paraprobiotics varies by market and is still evolving, so companies should not assume the same pathway as live probiotics.
Postbiotic
Bioactive compounds produced by probiotic microorganisms during fermentation, including metabolites, cell wall fragments, and secreted substances. Postbiotics can deliver health benefits such as anti-inflammatory activity, pathogen inhibition, and immune modulation without requiring live organisms. This makes them attractive for product formats where viability is difficult to maintain (heat-processed feeds, long shelf life products).
Dr. Nihan’s Note: The regulatory classification of postbiotics varies significantly by market and is still evolving. Companies developing postbiotic products for animals should not assume the same regulatory pathway as live probiotics. Check with a regulatory expert before you invest in formulation.
Prebiotic
A substrate (typically a non-digestible fiber or oligosaccharide) that selectively feeds and promotes the growth of beneficial microorganisms in the gut. Common prebiotics in animal nutrition include fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS), mannan-oligosaccharides (MOS), and inulin. Prebiotics work by shifting the gut environment to favor beneficial bacteria over potential pathogens.
Probiotic
Live microorganisms that, when administered in adequate amounts, confer a health benefit on the host (FAO/WHO definition). In animal health, probiotics are used across companion animals, poultry, ruminants, aquaculture, and equine species for digestive support, immune modulation, pathogen resistance, and performance optimization. The efficacy of a probiotic is strain-specific — two strains of the same species can have completely different effects.
Dr. Nihan’s Note: If a label just says “contains probiotics” without naming the specific strain, that tells you almost nothing. The strain is the whole story. Species-level identification is not enough. This is where most of the frustration vets and pet owners feel with probiotics actually begins.
S
SCFA (Short-Chain Fatty Acids)
Metabolic byproducts produced when gut bacteria ferment dietary fibers and prebiotics. The three main SCFAs — acetate, propionate, and butyrate — serve as energy sources for intestinal cells, strengthen the gut barrier, modulate the immune system, and regulate inflammation. SCFA levels are one of the most commonly measured biomarkers in animal microbiome research and are often used to evaluate the impact of probiotic and prebiotic interventions.
Shotgun Metagenomics (Whole Genome Sequencing)
A sequencing approach that reads all the genetic material in a sample, not just a targeted gene. Unlike 16S rRNA amplicon sequencing, shotgun metagenomics reveals both the identity and the functional potential of every organism in the community. It is more expensive and data-intensive but provides deeper insight into what the microbiome can actually do, not just who is present.
Strain Identification
The process of characterizing a probiotic microorganism down to the strain level (e.g., Lactobacillus rhamnosus GG, not just Lactobacillus rhamnosus). Strain identification uses genotypic methods such as whole genome sequencing, PFGE, or MLST to confirm that a specific isolate is distinct from other strains of the same species. Strain-level identity is essential because the health effects, safety profile, and regulatory status of probiotics are strain-specific.
Synbiotic
A product that combines probiotics and prebiotics in a formulation designed to work synergistically — the prebiotic selectively feeds and enhances the activity of the co-administered probiotic. True synbiotic design requires evidence that the specific prebiotic actually supports the specific probiotic strain included in the product, not just that both are present in the same formula.
Dr. Nihan’s Note: Putting a probiotic and a prebiotic in the same capsule does not automatically make it a synbiotic. The synergy has to be demonstrated. Many products use the term loosely without this evidence, which is a claims risk and a scientific shortcut.
#
16S rRNA Gene Sequencing
A molecular method used to identify and classify bacteria by analyzing the 16S ribosomal RNA gene, which is present in all bacteria and contains both conserved and variable regions. It is the most widely used technique for profiling bacterial communities in animal microbiome studies. While effective for identifying who is in the community, it does not provide direct information about what those bacteria are functionally doing.