Understanding What 'On an As-Fed Basis' Means

December 27, 2025 •

4 min read

The moisture content in a product can drastically affect its nutritional profile; for instance, a canned pet food that is 75% moisture will show a much lower percentage of protein on its label compared to a dry food, even if the actual nutrient levels are similar. This is because the phrase "on an as-fed basis" refers to the nutrient concentrations of a food as it is served, including all of its water content.

Quick Summary

This article explains the meaning of "on an as-fed basis," which is the nutritional measurement of a food including its moisture content. It clarifies why this metric can be misleading, especially when comparing wet and dry products, and details how to convert to a dry matter basis for accurate nutritional comparisons.

Key Points

As-fed Includes Moisture: 'On an as-fed basis' represents a food's nutrient levels exactly as it is fed, with its natural water content included.
Comparing Different Foods: Comparing as-fed percentages of wet and dry foods is inaccurate because of their differing moisture levels.
Dry Matter Basis for Comparison: To compare products fairly, nutrient values must be converted to a dry matter basis, which standardizes the analysis to 0% moisture.
Moisture Dilutes Nutrients: High-moisture foods have a lower concentration of nutrients on an as-fed basis, making them appear less potent than dry foods.
Convert to Dry Matter: To find a nutrient's dry matter value, subtract the moisture percentage from 100%, then divide the as-fed nutrient percentage by that dry matter percentage (as a decimal) and multiply by 100.
Crucial for Diet Formulation: For animals like livestock that consume high-moisture feed, knowing the dry matter intake is vital to ensure they receive sufficient nutrients.
Guaranteed Analysis vs. Dry Matter: The Guaranteed Analysis on pet food labels provides minimum and maximum nutrient levels on an as-fed basis, not the true dry matter concentration.

What is an "As-Fed Basis"?

In animal nutrition, the term "on an as-fed basis" (or "as-is") refers to the nutritional composition of a food as it is normally prepared and eaten, with its moisture included. This is the standard measurement you will find on the "Guaranteed Analysis" panel of pet food and animal feed labels. For example, the label on a can of wet dog food will list the protein percentage on an as-fed basis, meaning the percentage is based on the total weight of the food right out of the can, which often includes a high percentage of water.

This method of reporting provides a simple snapshot of the food's composition in its current state. However, it does not allow for a direct, equitable comparison between two products with different moisture levels. A wet food with 78% moisture will have its nutrients appear more "diluted" than a dry food with 10% moisture, simply because of the difference in water weight.

Why As-Fed Values Can Be Misleading

Many consumers make the mistake of comparing two pet food products side-by-side using only the as-fed values. This can lead to inaccurate conclusions about a product's nutritional potency. A canned food might list 10% crude protein, while a dry kibble lists 25% crude protein on their respective labels. Without considering moisture, one might assume the kibble is vastly superior in protein content. However, once the moisture is removed from the equation, a different picture emerges, as the wet food's protein percentage on a dry matter basis will be much higher due to the concentration of nutrients.

The Crucial Role of Dry Matter Basis

To make a fair comparison between different feed types, such as comparing a wet food to a dry food or two different types of forage, nutritionists and consumers must convert the as-fed values to a dry matter (DM) basis. The dry matter basis standardizes all nutritional information to a 0% moisture content, providing a true "apples-to-apples" comparison.

How to Convert from As-Fed to Dry Matter

Converting a nutritional value from an as-fed basis to a dry matter basis is a simple three-step calculation:

Find the Dry Matter Percentage: Subtract the moisture percentage (listed on the guaranteed analysis) from 100%. For example, if a food has 75% moisture, its dry matter content is 25% (100% - 75% = 25%).
Divide by Dry Matter: Divide the as-fed nutrient percentage (e.g., crude protein) by the dry matter percentage (as a decimal). Using the example above, divide the crude protein percentage by 0.25.
Multiply by 100: Multiply the result by 100 to get the nutrient percentage on a dry matter basis.

This calculation reveals the actual concentration of nutrients, allowing for a far more accurate evaluation of product quality and suitability for specific dietary needs.

Practical Application in Animal Feeding

For animals on a high-moisture diet like fresh pasture or silage, understanding the dry matter intake is critical. A large quantity of high-moisture feed is needed to meet the same dry matter requirements as a smaller quantity of dry feed. For example, a horse needing 22 pounds of dry matter per day would have to consume significantly more fresh pasture (15% DM) than hay (90% DM) to meet its needs. Correctly calculating dry matter intake prevents underfeeding or overfeeding and ensures the animal receives the correct balance of nutrients for its health and performance.

As-Fed vs. Dry Matter Basis Comparison


Feature	As-Fed Basis	Dry Matter (DM) Basis
Moisture Content	Included	Excluded (0%)
Purpose	Represents the food as it is served; used for mixing and feeding.	Standardizes nutrient values for accurate product comparison.
Nutrient Values	Diluted by moisture, appearing lower for wet foods.	Concentrated, providing a truer percentage of nutrients.
Best For	Daily feeding calculations and measuring physical weight of feed.	Comparing nutritional potency between wet, dry, or fresh feeds.
Labeling	Found on most Guaranteed Analysis panels.	Usually not on the label; requires calculation to determine.

Why This Understanding Is Important

Beyond simply comparing pet foods, understanding the as-fed and dry matter distinction is vital for anyone involved in animal feeding, from pet owners to livestock farmers and veterinary nutritionists. It allows for informed decisions regarding diet formulation, ensuring that an animal's specific dietary requirements are met, particularly for those with health conditions. In commercial settings, this knowledge helps producers accurately formulate and mix rations, especially when dealing with raw materials that have variable moisture content, such as byproducts or fresh forages.

For example, formulating a ration on an as-fed basis using ingredients with fluctuating moisture levels can lead to inconsistencies in the final diet. By converting all components to a dry matter basis, nutritionists can create a precise recipe that delivers consistent nutrient levels, regardless of ingredient variation. The ability to accurately compare products and formulate diets is a foundational skill for maintaining animal health and performance. This dual understanding of how nutrients are expressed—both with and without moisture—is the key to unlocking true nutritional transparency.

Conclusion

The phrase "on an as-fed basis" is a straightforward, literal description of a food's nutritional content, including its moisture. While useful for daily feeding, it can be misleading for comparative analysis between different types of food. The dry matter basis, which removes all moisture from the equation, offers a more accurate method for evaluating and comparing nutrient concentrations. By understanding and utilizing both measurements, pet owners and animal caretakers can ensure their animals receive the optimal nutrition required for their health and well-being. Ultimately, informed nutritional decisions hinge on looking past the label's initial percentages and converting them to their true dry matter value. For further reading, consult the World Small Animal Veterinary Association's (WSAVA) global nutrition guidelines, which offer valuable insights into pet food selection: https://wsava.org/global-guidelines/global-nutrition-guidelines/.

Frequently Asked Questions

To convert a nutrient to a dry matter basis, first subtract the food's moisture percentage from 100% to find the dry matter percentage. Next, divide the as-fed nutrient percentage by the dry matter percentage (as a decimal) and multiply by 100.

The primary reason is to allow for an accurate, standardized comparison of the nutritional content between foods with different moisture levels. This prevents the misinterpretation of nutrient concentrations caused by water weight.

Dry food appears to have a higher protein percentage on its as-fed label because it has a much lower moisture content. The same amount of protein is therefore more concentrated in a smaller total weight, while a wet food's protein is diluted by its high water content.

'As-fed' and 'as-is' are synonymous terms in the context of animal nutrition and feed analysis. They both refer to the nutritional values of the food in its natural, moisture-included state.

Yes, as-fed basis directly affects the quantity you feed. Since it includes water, you will need to feed a larger physical weight of a high-moisture food (e.g., canned food or fresh forage) to deliver the same amount of nutrients as a smaller weight of a dry food.

Yes, it is generally acceptable to compare two products with very similar moisture content using their as-fed values. However, converting to a dry matter basis is still the most precise method for any comparison.

Yes, according to the U.S. Food and Drug Administration (FDA) and Association of American Feed Control Officials (AAFCO) guidelines, the Guaranteed Analysis on a pet food label must be expressed on an as-fed basis, including the moisture.