WildAgain Wildlife Rehabilitation, Inc.

Wet matter versus dry matter basis
What's the difference?


This web site provides considerable quantitative data about various milk replacer products – both in dry form and wet form. The DRY form is for the powder in its original packaging prior to mixing with water. The wet form is after mixing the powder with water and ready for feeding. The component percentage values for solids and moisture are significantly different depending on whether the product is in its dry or wet form.

Consider columns B and C in the table below. Column B shows the values for liquid Esbilac® with solids at around 15%. That means most of the can is water. Column C shows the values for powdered Esbilac® with solids around 95%. Most of the can or bag is dry powder, with very little moisture or water content. Thus the more solids a product contains, the more nutrients such as protein, fat, carbohydrates, minerals, etc.

Knowing the dry matter values are beneficial in two ways. First, they give a basis to compare to values of the other products, making sure they are compared on a dry to dry basis, such as shown on the page displaying values form the proximate analysis. Second, they provide the user with a starting point to estimate what the wet values will be when mixed with water.

The table below and the accompanying explanations provide a more thorough overview of the difference between wet and dry matter values. It shows an example for the Eastern gray squirrel, comparing the values of the mother squirrels milk to a formula based on using powdered Esbilac®. Similar comparisons may be developed for other species.

  A   B   C D E F G H

Ea. gray squirrel mother's milk

Esbilac® sold as liquid in a can Esbilac® powder (Lot#3419E)
  Wet Matter Wet Matter Dry Matter (powder in the can) Wet Matter  (formula ready to feed)
    Powdered Esbilac® label Midwest Lab test results
1 part Esbilac®
2 parts water
(as per label instructions)
1 part Esbilac®
1.75 parts water
.25 heavy cream
As-fed Ready to use, as-fed (Prior to mixing with water) As-mixed, as-fed % of mother's milk As-mixed, as-fed % of mother's milk
Solids % 26.5 > 15 > 95 95.6 18.1 68% 22.4 85%
Protein % 9.0 > 4.5 > 33 38.8 7.2 80% 7.4 82%
Fats % 12.5 > 6.0 > 40 42.2 7.9 63% 11.7 94%
Kcals/gr 1.6   .82   .90 5.13 .99 62% 1.35 84%
  Wet matter
  Dry matter

Column A. This column shows the values for the Eastern gray squirrel mother’s milk based on a average of the values reported in the studies conducted by Shaul (1962) and Nixon and Harper (1972). Values shown are for the percent of total solids, protein and fat as contained in the milk. The calorie value for 1cc of milk is also shown, using the modified Atwater/AAFCO calculation. These values are used a reference point when designing any formula based on using one or more of the powdered milk replacer products.

Column B. This column shows the values for Esbilac® sold as liquid in a can. Most rehabilitators do not purchase this form of milk replacers, as they are more expensive, require more storage space than powdered products, and once opened, must be used quickly.

Column C. This column shows the values for Esbilac® powder. This is the form of milk replacers preferred by most rehabilitators due to cost and storage. These values are listed on the labeling for the product and indicate either minimums or maximums, commonly referred to as the Guaranteed Analysis. Note: The value for kcals is not provided on a dry basis on the label, but is only reported for a formula reconstituted for 1 part of the powder mixed with 2 parts of water.

Column D. The values in this column are the results of laboratory testing by Midwest Labs. A proximate analysis was performed as well as a mineral analysis. These are all dry matter values, and are much more precise than the Guaranteed Analysis values shown in column C. These values are accurate to within the +/- 2% generally accepted analytical measurement error.

Columns E and F. These values in column E are for a wet formula that was prepared using one part powder and two parts water, as directed on the Esbilac® label.  The percentage values for solids, protein and fat are much reduced than the values in Column C since the powder was been diluted during the mixing with water. Column F shows that this formula falls below the values for the mother’s milk (Column A) by 60-80%.

Columns G and H. These values in column G are for a wet formula that was prepared using one part powder; 1.75 parts water; and .25 part heavy whipping cream.  Again, the percentage values for solids, protein and fat are much reduced than the values in Column C since the powder was been diluted during the mixing with the water and cream. But as shown in Column F, this formula more closer matches the values for the mother’s milk (Column A), within about 85-95%. To prepare a formula that approached 100% of mother’s milk would require a level of solid matter that is not tolerated by young squirrels in rehabilitation.  While mother’s milk does in fact contain more solids, it is much more tailored to and digestible by the squirrel’s digestive system than a commercial milk replacer powder.


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