In pet food development, increasing attention is being paid to the role of short-chain fatty acids (SCFAs). SCFAs include acetate, propionate, and butyrate, all of which are fatty acids with relatively short carbon chains (typically C2–C4). These compounds are primarily produced when intestinal microbiota ferment dietary fibers and other indigestible components, and they exert a wide range of physiological effects within the gastrointestinal tract of dogs and cats.
This article provides pet food development managers with a comprehensive overview of SCFAs, covering their basic characteristics, effects on gut microbiota and immune function, impacts on digestion and nutrient utilization, palatability considerations, safety, and examples of application and market trends in Europe and North America.
Types of Short-Chain Fatty Acids and Their Physiological Roles
SCFAs are broadly classified into the following types, each with distinct physiological functions.
In addition to these straight-chain SCFAs, branched-chain fatty acids (such as isobutyrate and isovalerate) are produced through bacterial fermentation of proteins. However, excessive production of branched-chain fatty acids is associated with foul odors and deterioration of the gut environment. Therefore, pet food formulation generally focuses on promoting beneficial SCFAs—acetate, propionate, and butyrate—derived from carbohydrate fermentation.
Effects on the Gut Microbiota
SCFAs are closely involved in maintaining the balance of the gut microbiota. In the large intestine of dogs and cats, dietary fibers and other indigestible components are fermented by intestinal bacteria, resulting in the production of acetate, propionate, and butyrate.
These SCFAs lower intestinal pH, thereby inhibiting the proliferation of pathogenic bacteria and creating an environment favorable to beneficial microbes. For example, diets supplemented with organic acids have been shown to suppress colonization by harmful bacteria such as Clostridium perfringens and reduce the production of toxic metabolites like ammonia.
Numerous studies also demonstrate that feeding prebiotics—fermentable, non-digestible fibers—shifts the gut microbiota toward a beneficial composition and increases SCFA production. Diets formulated with appropriate fiber sources have been reported to increase fecal SCFA concentrations and microbial diversity.
In one study, dogs fed a diet containing 9% apple-derived fiber (apple pomace) showed a significant increase in fecal butyrate levels and microbial diversity. These findings indicate that enhancing SCFA production contributes to gut health and may help prevent or manage gastrointestinal disorders.
Differences in Fermentation Capacity Between Dogs and Cats
It is important to recognize that dogs and cats differ in their intestinal fermentation capacity. Species with a more carnivorous diet generally have shorter gastrointestinal tracts and produce lower amounts of SCFAs from fiber fermentation.
Cats, in particular, have shorter intestines and a more limited ability to ferment dietary fiber compared with dogs. As a result, total fecal SCFA concentrations in cats are typically lower. However, the inclusion of appropriate amounts of fermentable fiber can still promote the growth of butyrate-producing bacteria and improve gut health in cats.
Reports in cats with chronic enteritis suggest that changes in butyrate-producing bacterial populations are associated with fluctuations in fecal butyrate levels, indicating that butyrate may serve as a meaningful marker of intestinal health even in feline nutrition.
Overall, SCFAs function like a lubricant that helps maintain gut microbiota stability. Strategically promoting SCFA production through prebiotic use represents a promising approach to supporting gastrointestinal health in both dogs and cats.
Effects on Immune Function and Anti-Inflammatory Activity
Among SCFAs, butyrate is particularly well recognized for its immunomodulatory and anti-inflammatory effects. In addition to serving as an energy source for intestinal epithelial cells and reinforcing the gut barrier, butyrate directly influences immune cells and inflammatory pathways.
Butyrate suppresses the NF-κB signaling pathway, reducing the production of pro-inflammatory cytokines by macrophages and epithelial cells, as well as lowering the generation of inflammatory mediators such as nitric oxide (NO). This results in attenuation of local intestinal inflammation and may contribute to symptom relief in inflammatory bowel disease.
Butyrate has also been shown to activate the cholinergic anti-inflammatory pathway of the enteric nervous system, thereby modulating systemic immune responses.
Anti-Inflammatory Regulation of Gut Immunity
Furthermore, butyrate and its derivatives are thought to promote the induction of regulatory T cells and maintain immune tolerance at the epithelial level, based on evidence from human and murine studies. SCFAs bind to G protein–coupled receptors (such as GPR41 and GPR43) expressed on intestinal epithelial cells, transmitting anti-inflammatory signals throughout the gut immune system.
Propionate has also demonstrated anti-inflammatory effects, including modulation of cytokine production by dendritic cells.
Prevention and Improvement of Intestinal Disorders
The beneficial effects of SCFAs on immune function extend to the prevention and management of intestinal diseases. In dogs and cats with chronic enteritis or inflammatory bowel disease, fecal concentrations of acetate and propionate are often reduced, reflecting dysbiosis and ongoing inflammation.
Experimental studies have shown that oral supplementation with butyrate salts can suppress the onset of enteritis and colitis in animal models, suggesting potential applications for preventing colonic inflammation and irritable bowel–like symptoms in pets.
In addition, butyrate has been reported to exert antitumor effects by inducing apoptosis in cancer cells and to possess antioxidant properties, which may contribute to reduced colorectal cancer risk.
Effects on Digestion and Nutrient Utilization
SCFAs influence digestion and nutrient utilization in multiple ways.
Energy Supply
In dogs, SCFAs are estimated to contribute approximately 5–7% of total energy intake. After absorption, they are metabolized in the liver and muscle tissues. Although cats derive less energy from fermentation, fermentable fibers are sometimes used in renal diets for senior cats to reduce reliance on protein-derived energy and nitrogen waste production.
Studies have shown that adding fermentable fibers such as guar gum or beet pulp to low-protein diets increases fermentation-derived metabolites like propionate, which can be utilized in the citric acid cycle, thereby sparing protein breakdown.
Improvement of Gastrointestinal Function
SCFAs stimulate colonic motility and promote sodium and water absorption in the large intestine, contributing to improved stool consistency and reduced diarrhea. Lower colonic pH may also enhance the solubility and absorption of minerals such as calcium and magnesium.
Gastric Digestive Support
The inclusion of organic acids (e.g., lactic acid or propionic acid) in pet food can lower gastric pH, enhancing pepsin activity and improving initial protein digestion. Organic acids also help control gastric microbial populations, reducing protein putrefaction in the colon and lowering fecal ammonia levels.
Potential Risks of Excessive Fiber
Excessive inclusion of fermentable fibers such as inulin or fructooligosaccharides (FOS) can reduce protein digestibility by altering intestinal transit time or fermentation dynamics. Therefore, functional fiber levels must be carefully optimized to avoid compromising overall nutritional balance.
Effects on Palatability
Maintaining palatability is a constant challenge in pet food development. High-fiber diets are often associated with reduced palatability due to changes in flavor and texture. Studies have shown that adding certain fibers, such as sugarcane fiber or wheat bran, can introduce bitterness or earthy flavors.
However, palatability can be preserved or even improved depending on fiber source and processing. Apple pomace, for example, contains natural sweetness and aroma and has been shown to maintain or increase intake even at inclusion levels as high as 9%.
Technologies such as microencapsulation can also help mask undesirable textures and deliver fibers or SCFAs more effectively to the intestine.
Palatability of SCFAs Themselves
Pure butyric acid has a strong odor resembling rancid butter, making direct inclusion impractical. However, encapsulated forms or glyceride derivatives (e.g., tributyrin) allow odor reduction and controlled release.
Propionic acid, commonly used as a preservative at 0.1–0.3%, generally does not negatively affect palatability and may even enhance intake by stabilizing flavor and preventing oxidation.
Safety and Appropriate Usage Levels
SCFAs are naturally produced in the gut and are generally safe when used appropriately. Regulatory evaluations in Europe indicate high safety margins for propionic acid and butyrate salts. Typical inclusion levels in pet food are well below established safety thresholds.
Importantly, “more is not always better.” Excessive concentrations of butyrate can induce epithelial cell apoptosis and damage the gut barrier in experimental models. Therefore, appropriate dosing and gradual evaluation are essential, particularly when using SCFA supplements.
Similarly, excessive dietary fiber can impair nutrient absorption and cause soft stools or diarrhea. In most formulations, total dietary fiber is kept below the low double-digit percentage range, except in therapeutic diets.
Long-term studies have not identified significant adverse effects from prolonged use of prebiotics such as FOS or inulin, and these ingredients generally demonstrate high tolerability compared with live probiotics.
Applications and Market Trends in Europe and North America
Mainstreaming of “Gut Health”
In Europe and North America, “gut health” and “microbiome” have become central themes in pet food marketing. Prebiotics such as FOS, chicory-derived inulin, and beet pulp are now standard ingredients in many premium diets, supported by growing scientific evidence.
Toward Personalized Nutrition
The trend toward personalized nutrition is also emerging in pet food. Research suggests that different fiber sources generate distinct SCFA profiles depending on individual microbiota composition. This opens the door to customized fiber blends tailored to specific breeds or individual pets.
Postbiotics and Direct SCFA Supplementation
Products containing encapsulated butyrate or tributyrin are increasingly available as supplements or adjuncts to therapeutic diets. These “postbiotic” approaches deliver fermentation products directly, complementing traditional prebiotic strategies.
Reassessment of Organic Acids
Organic acids such as propionic and acetic acid are also being reevaluated not only as preservatives but as functional ingredients that support gut health and stool quality, particularly in high-protein diets.