Crude Fiber vs. Dietary Fiber in Pet Food: What Changes Under AAFCO PFLM?

Crude Fiber vs. Dietary Fiber in Pet Food

What Is Crude Fiber in Pet Food?

Crude fiber is an analytical measurement that has historically been used in animal feed and pet food labeling. Under the traditional pet food Guaranteed Analysis, the basic nutrient guarantees include minimum crude protein, minimum crude fat, maximum crude fiber, and maximum moisture. The term "crude" refers to the analytical method rather than the quality of the nutrient or ingredient.

The crude fiber method uses a series of chemical digestion steps to measure a portion of the fibrous material remaining in the food. The limitation is that some fiber components are lost during the analytical process. 



Crude fiber values are commonly only about 30% to 50% of actual dietary fiber concentrations. The method does not adequately account for all soluble and insoluble dietary fiber fractions. For this reason, crude fiber has provided a standardized regulatory value, but it is not considered a complete measurement of the fiber contained in a pet food.

What Is Dietary Fiber in Pet Food?

Dietary fiber is a broader analytical measurement designed to capture more of the carbohydrate components that resist digestion by mammalian digestive enzymes.

Unlike crude fiber testing, total dietary fiber methods account for both insoluble dietary fiber and soluble dietary fiber. Depending on the ingredients and analytical method, dietary fiber can include fiber fractions that crude fiber testing does not fully recover.

This distinction can be particularly important in pet foods containing ingredients that contribute different types of fiber. Fiber sources may behave differently during crude fiber analysis, so two formulations with similar crude fiber values do not necessarily contain similar amounts or types of dietary fiber.



AAFCO specifically identifies dietary fiber as a better measure of fiber in its Pet Food Label Modernization materials.

Crude Fiber vs. Dietary Fiber: What's the Difference?

The primary difference between crude fiber and dietary fiber is what the analytical method actually measures.

Crude fiber:

• Measures only a portion of the fiber in a pet food
• Primarily captures certain insoluble fiber fractions
• Can lose soluble fiber and other fiber components during analysis
• Has traditionally been reported as a maximum guarantee in the pet food Guaranteed Analysis

Dietary fiber:

• Measures a broader range of fiber components
• Includes both soluble and insoluble dietary fiber
• Provides a more complete estimate of the fiber present in the food
• Is used as the maximum fiber guarantee in AAFCO's new Pet Nutrition Facts model

Because these methods measure different fractions of a food, a crude fiber result cannot simply be treated as a dietary fiber result.

Why Are Crude Fiber and Dietary Fiber Results Different in Pet Food?

The difference comes primarily from the analytical methods. During crude fiber analysis, portions of the food's fiber can be dissolved or removed as the sample undergoes chemical treatment. This means the final crude fiber value may substantially underestimate the total amount of dietary fiber in the food.

Total dietary fiber methods are designed to retain and quantify a broader range of soluble and insoluble fiber fractions. In its review of fiber testing methods, Fahey and colleagues concluded that total dietary fiber methods provide a more complete measurement than crude fiber analysis.

For example, a pet food with a crude fiber value of 4% should not automatically be assumed to contain 4% dietary fiber. The dietary fiber concentration could be considerably higher depending on the formulation and fiber sources.



There is no universal conversion factor that can reliably turn a crude fiber result into a dietary fiber value. Appropriate dietary fiber testing is needed to establish the dietary fiber concentration of a specific product.

How Does AAFCO PFLM Change Crude Fiber and Dietary Fiber Labeling?

AAFCO's Pet Food Label Modernization initiative represents the first major restructuring of its model pet food labeling regulations in decades. The new format replaces the traditional presentation of nutrition information with a standardized Pet Nutrition Facts box intended to provide nutritional information in a more consistent format.

One of the most significant nutritional changes is the treatment of fiber.

Under Regulation PF5 of the AAFCO PFLM model regulations, the Pet Nutrition Facts format includes:

• Protein, minimum
• Fat, minimum
• Total Carbohydrate, maximum
• Dietary Fiber, maximum
• Moisture, maximum
• Other required or voluntary nutrient guarantees when applicable



AAFCO's PFLM materials specifically state that total carbohydrate and dietary fiber guarantees replace the crude fiber guarantee. Total carbohydrate is identified as a calculated value, while dietary fiber is included as a maximum guarantee.

This does not mean every pet food label nationwide changed at the same time. AAFCO develops model regulations, while individual states determine whether and how those regulations are adopted. AAFCO recommends a six-year transition period as states implement the new requirements.

Can an Existing Crude Fiber Result Be Used for a Dietary Fiber Guarantee?

Not directly.

Because crude fiber and dietary fiber measure different components, an existing crude fiber result cannot simply be transferred to the Dietary Fiber line of a Pet Nutrition Facts panel.

A product transitioning from the traditional Guaranteed Analysis to a PFLM-style Pet Nutrition Facts panel may therefore need updated pet food dietary fiber testing rather than relying solely on historical crude fiber data.

This distinction becomes especially relevant for products formulated with multiple or complex fiber sources. Similar crude fiber values do not necessarily indicate similar dietary fiber concentrations because the analytical methods recover different fiber fractions.

What Does AAFCO PFLM Mean for Pet Food Fiber Testing?

The change from crude fiber to dietary fiber affects more than label terminology. It changes the nutritional information needed to support the fiber guarantee.

When preparing nutritional data for the Pet Nutrition Facts format, testing and calculations may include:

• Protein
• Fat
• Dietary fiber
• Moisture
• Ash
• Total carbohydrate calculations
• Additional nutrients associated with nutritional or functional claims

AAFCO's model Pet Nutrition Facts format also reports nutrient guarantees using a familiar household unit, such as a cup, can, treat, or piece, along with the weight of that serving in grams. The format also includes calorie information and calories contributed by protein, fat, and carbohydrate.

Products with existing nutrition data based on a traditional proximate analysis may therefore require review before transitioning to the new format. If the available data only include crude fiber, additional dietary fiber analysis may be necessary to establish an appropriate label guarantee.

Why Is Dietary Fiber a More Useful Measurement?

Crude fiber has served as a standardized analytical measurement for pet food for many years, but it captures only part of the fiber contained in a product.

Dietary fiber testing provides a broader picture because it accounts for both soluble and insoluble dietary fiber. This can provide more meaningful information about the actual fiber composition of a pet food and is one reason AAFCO selected dietary fiber for the updated Pet Nutrition Facts format.

As pet food labeling transitions under AAFCO PFLM, the important distinction is straightforward: crude fiber and dietary fiber are different analytical measurements, and their values are not interchangeable.

Reviewing existing nutritional data and understanding which fiber method was used can help identify whether additional testing is needed before establishing dietary fiber guarantees for updated pet food labels.

Frequently Asked Questions About Crude Fiber and Dietary Fiber

Is crude fiber the same as dietary fiber in pet food?

No. Crude fiber measures only part of the fiber present in a pet food. Dietary fiber methods measure a broader range of soluble and insoluble fiber components, so dietary fiber values are often higher than crude fiber results.

Will AAFCO PFLM replace crude fiber with dietary fiber?

Under AAFCO's PFLM model regulations, dietary fiber replaces crude fiber as the fiber guarantee in the Pet Nutrition Facts format. Total carbohydrate is also added as a maximum calculated value. Implementation depends on adoption of the model regulations by individual states.

Can crude fiber be converted to dietary fiber?

There is no reliable universal conversion between crude fiber and dietary fiber. The methods measure different fiber fractions, so dietary fiber testing is needed to determine the appropriate value for a specific pet food formulation.

Resources

Association of American Feed Control Officials. Pet Food Label Modernization 

Association of American Feed Control Officials. PFLM Pet Food Label Comparison 

U.S. Food and Drug Administration. Animal Food Labeling and Pet Food Claims