OsmoCalc Demo Milk Additives
Hello and welcome to this OsmoCalc Knowledge Base video. In this episode, we’ll look at how different feed additives affect the osmolality of whole milk.
To begin, we’ll adjust the calculator to represent whole milk as the only liquid feed. In the first column, we’ll select whole milk from the Typical menu. We’ll set the feeding rate to two liters per day and reduce added water to zero. Now the solution contains only whole milk. In this example, the milk composition is about 3.4% protein, 4.0% fat, and 0.7% ash. The calculated osmolality is approximately 267 milliosmoles per kilogram, which is within the typical range for whole milk—generally between about 280 and 300 milliosmoles per kilogram, depending on composition.
Changes in protein and fat alter the proportion of lactose, and lactose is a major contributor to osmolality. As lactose concentration increases, osmolality increases as well.
Next, we’ll add a feed additive. By clicking the Additives menu button, a new column appears to the right of the water column. We now have three columns in the nutrient grid: whole milk, water, and additives.
For this example, we’ll use a typical whole milk fortifier. These products are designed to increase vitamin and mineral concentrations in whole milk and may also carry additional ingredients such as probiotics or medications. We’ll assume a representative composition: approximately 97% dry matter, about 6% protein, 1% fat, and roughly 33% ash. Much of the product consists of minerals, which contribute substantially to osmolality. We’ll also assume about 5% dextrose as a carrier and a small amount of lactose, perhaps from dried whey.
Mineral inclusion might include approximately 0.5% sodium, 1% potassium, 1% calcium, and 0.8% phosphorus. Trace minerals—such as copper, iron, manganese, zinc, cobalt, and selenium—are present in very small concentrations and contribute essentially nothing to total osmolality because of their low inclusion rates.
If we feed this fortifier at 25 grams per two liters of whole milk, the final osmolality increases to just over 300 milliosmoles per kilogram. Without the additive, the milk begins at about 293 milliosmoles. Thus, the fortifier contributes roughly 45 milliosmoles to the total solution. Most of this increase comes from added minerals and carbohydrates. Trace minerals have a negligible effect.
Now let’s examine a second additive: a typical oral electrolyte product. Occasionally, producers mix electrolytes directly into whole milk in an attempt to reduce the number of feedings when calves have scours. This practice is not recommended for several reasons, and osmolality is one of them.
We’ll select a representative electrolyte from the typical menu. This electrolyte containing about 5% protein, 15% ash, and roughly 70% dextrose. It also contains components such as bicarbonate, glycine, acetate, or propionate—each of which contributes to total osmolality.
If we add electrolytes at a typical feeding rate of 100 grams, the solids concentration increases dramatically. In this example, total solids rise to about 17%, and the final osmolality exceeds 800 milliosmoles per kilogram. This is well above the recommended range for calf feeding.
Such high osmolality can significantly delay abomasal emptying, increasing the risk of digestive disturbances. In severe cases, this may predispose calves to bloat, including bloat associated with organisms such as Clostridium perfringens.
This example clearly demonstrates the profound impact that certain additives—particularly electrolytes—can have on the osmolality of whole milk. Understanding these effects helps us make better feeding decisions and avoid unintended consequences.
That concludes this demonstration. Thanks for watching, and be sure to explore the other OsmoCalc Knowledge Base videos to learn how to get the most from the program.
