Milk Replacer Products For Wildlife -
What does '33/40' really mean?
Milk replacer product naming
The two primary manufacturers of powdered milk replacer products used by rehabilitators name many of their products with a pair of numbers such as 33/40; 30/50; 40/25; etc. etc. Do these numbers mean something or are they simply arbitrarily assigned numerical labels?
In almost all cases they refer to the guaranteed minimum of protein and fat (in percentage terms) for the total product. For example, a 33/40 product would contain a minimum of 33% protein and a minimum 40% of fat. Or at least they should. Recent lab tests indicate that most of the products tested usually meet the minimum protein content values. However, the values for fat, as tested, are mostly falling short and not adhering to the guaranteed minimum as disclosed on the product label.
Some products, such as Esbilac®, KMR®; and GME®, use those respective trademark brand names for the products in lieu of a '33/40' or '42/25' designation. PetAg's line of Zoologic® products uses the numbers, as does Fox Valley for its products. Except when they do not - such as for PetAg®'s MultiMilk® and Fox Valley's UltraBoost.
The common denominator
Let’s use the example of 33/40. The important thing to remember is that the first number (33%) refers to the guaranteed minimum of protein in the product and the second number (40%) refers to the guaranteed minimum of fat in the product. It really is that simple and that is what all those numbers refer to.
As the lab tests have shown, any given lot of a product will rarely be EXACTLY 33/40 . True, but the expectation should be that the product will test close to those numbers, and not BELOW those numbers (since they are “guaranteed MINIMUM values”). This is where WildAgain's posting of the test results for the various products can offer insights as to which products are more consistently true to those guaranteed values (either over or under), as well as trends over several years.
When considering a recipe for a formula, the 33/40 values on the product label provide one of the best starting points for determining a recipe that proportionately matches the mother's milk of the species.
But wait (again)!
Why do I need to consider a match to mother's milk since some of the labels indicate which product should be fed to an individual species (such as most of the Fox Valley product labels)? Can't I just rely upon that? This seems like extra work.
Let's review again what 33/40 means...
Again, it only means the guaranteed value for the percent content of protein and fat in the product. Period. Full stop.
Consider the chart below. The chart plots the protein content value along the horizontal axis and the fat value along the vertical axis. The values for mother's milk are all adjusted to a 5% moisture content, which is the same as the guaranteed value for the powder, or 5% moisture (aka apples to apples).
The most logical place to start when considering a recipe for a formula is looking at the various published mother's milk studies, and not simply relying upon a label recommendation. Since Fox Valley provides these label recommendations, let's compare their recommended product (for squirrels) with the two different milk composition studies for squirrels (plotted below, about the center of the chart).
One of Fox Valley's products on the chart, 20/50, is recommended for squirrels. If we are trying to most closely match mother's milk, it would seem that there are other product choices to consider that have more comparable protein/fat contents to squirrel milk, such FV32/45; FV32/40; FV30/40; and FV34/40. There is no guarantee that they would produce better results as part of a formula recipe for squirrels, but it sure seems that one or more of them are worth considering.
In another example, Fox Valley recommends their FV30/40 for mule deer. Focusing on the protein/fat values (and not the label recommendation), the FV33/30 and FV35/33 products might provide formulas more closely matched to mother's milk.
It's all about the numbers (not the marketing)
If the rehabilitator's goal is to create a recipe that best matches mother's milk, more focus should be on the composition of the product, especially in terms of the protein and fat content, and less on catchy product names and label recommendations. As a rehabilitator, it is critical to take the time to understand the nutritional composition of the products, and then use one or more products (yes, consider blending) to create a recipe that best matches the mother's milk. [TIP: Think of all of the powdered milk replacer products as dry INGREDIENTS of a formula recipe prior to adding the water, rather than as THE FORMULA in its final liquid form.] WildAgain's Wildlife Formula Calculator includes many ingredients (milk replacers, fats, supplements – and a way for you to add others you may consider) and can do the math for you. Plus, it contains many of the mother's milk study values, as well as the lab tests for individual products. Remember, this is just math: the real proof is how any recipe/formula actually works when fed to the wild mammal babies.