Whole milk versus milk replacer

We frequently compare whole milk and milk replacer when discussing dairy calf nutrition.  It is difficult to offer sound advice or make appropriate decisions on which liquid diet to offer calves unless we understand how they are different.  It also is critical for understanding the different challenges that may occur with each feeding program.

It’s my opinion that whole milk is as near the perfect food as we have available.  Momma cow gets it right by producing nutrient-packed milk for her calf.  That said, there can be some serious challenges to feeding whole milk and, in those situations, offering calves a high-quality milk replacer may be the best option for the producer and the calf.

Let’s start by evaluating Table 1 and noting some macro differences between whole milk and a couple milk replacer formulations.

Table 1. Average whole milk composition compared with two different milk replacers.
	Whole milk		Traditional 20/20 milk replacer	Talon 25/25 milk replacer
	Wet basis	Dry basis	Wet basis	Wet basis
Water	87.1	0.0	3	3
Protein	3.2	24.8	20	25
Fat	4.0	31.0	20	25
Lactose	5.0	38.8	49	41
Ash	0.7	5.4	8	6
Total solids	12.9	100	97	97

To start, whole milk is usually going to be between 12.5% and 13% solids on-farm.  For this example, I’ve selected what I would expect from an average Holstein.  Lactose and ash are going to be consistent at 5% and 0.7%, respectively.  Protein should be in the 3.1% to 3.4% range and fat may be a bit more variable coming in between 3.7% and 4.4%.

To compare this to what we see in a bag of milk replacer, we need to convert those numbers from wet basis to dry basis.  To do this, simply select a component, like protein, at 3.2% and divide it by the total solids of 12.9% and then multiply by 100.

3.2/12.9 × 100 = 24.8% dry basis

While milk replacer is not completely dry coming out of the bag, it only contains 3% moisture, which allows for a fair comparison once whole milk components have been converted to dry basis.

A few key things to note with whole milk:

One potential driver of improved health may be lower osmolality of milk replacer with increased fat content.  This directly ties into the next observation.  Lactose and ash are low in whole milk, especially when compared with more traditional milk replacers.  This is important because the primary drivers of osmolality within milk and milk replacer are lactose and ash.

Increased osmolality is associated with impaired intestinal barrier function or “leaky gut.”  The osmolality of milk is approximately 290 mOsm/L, while traditional milk replacer and Talon, mixed at 13% total solids, are approximately 420 mOsm/L and 368 mOsm/L, respectively.

Table 1 also demonstrates that not all milk replacers are created equal.  For example, Talon is close to whole milk for protein, lactose and ash content.  Most importantly, lactose and ash are reduced in Talon compared with a traditional 20/20 milk replacer.

What’s best for your calves?  As always, the answer is “it depends.”  While whole milk is close to nature’s perfect food, we must remember that whole milk and waste milk are not the same.  Whenever we collect and store milk to feed calves, we are introducing the risk of bacterial contamination.  If we can collect, pasteurize and feed whole milk without excessive bacterial growth, it can be a great option.  However, in situations where producers want simplicity and consistency, or when milk price is high and we want to sell as much as possible, the right milk replacer can be an equally good option.