Should I Add Electrolytes to Milk or Milk Replacer?
Whole milk and milk replacers are not just complete feeds for calves, they are also an excellent medium for delivering many nutritional additives. Oral electrolytes, however, are not one of them.
It has to do with the concentration of particles in the liquid, measured as millimoles/liter (mmol/L). This concentration is referred to as the osmolarity of the liquid. Milk is about 300 mmol/L. Milk replacer, which contains an excellent source of supplemental minerals and vitamins, is more concentrated, and is typically between 450 and 550 mmol/L once it’s mixed with water.
Now let’s take a look at oral electrolyte products. To be specific, we’re talking about powdered electrolytes. Their osmolarity ranges from around 300 to over 700 mmol/L once the powder is mixed with water.
Putting a packet of electrolytes into 2 quarts of milk increases its normal osmolarity from 300 to between 600-1000 mmol/L. In milk replacer, osmolarity jumps up between 750-1250 mmol/L. The change in osmolarity is not quite as big for calves receiving 3 quarts rather than two. In this case, the osmolarity of milk after adding electrolytes is between 450-700 mmol/L and between 600-900 mmol/L for milk replacer.
The reason all of this is important is that consuming liquids that are greater than 600 mmol/L can affect the calf’s digestion. Rate of passage slows down, giving bacteria a chance to grow and overproduce resulting in production and accumulation of gas and toxins. In addition, the calf moves more water from its body into its digestive tract to help dilute the contents, which can lead to dehydration and worsen water loss.
Scouring calves are in serious need of additional water, and the sodium and glucose in electrolytes have a big role in enhancing water absorption in this critical situation. Adding electrolytes to milk or milk replacer does nothing to help! And don’t assume that oral electrolyte products with instructions that encourage their addition to milk and milk replacer have somehow overcome these relationships.