Proper Milk Replacer and Water Feeding

By Rodney Dennis, Dairy Nutritionist/Calf Specialist

Why should milk replacer be mixed and fed according to directions?

Nutrients are absorbed by osmosis. In mammalian physiology, all body fluid compartments contain 300 milliosmols of osmolarity. So for optimal absorption (osmosis) of nutrients by the calf, the milk replacer should be around 300 milliosmols. Properly mixed calf milk replacer will contain 260-280 milliosmols of osmolarity, which is ideal for best absorption and digestion of the milk replacer.

What occurs if calf milk replacer is mixed too concentrated?

  • If calf milk replacer is mixed more concentrated than labeled mixing directions (for example 10 oz. in 1 quart of water instead of 2 quarts), the resulting mix will be too concentrated (500-520 milliosmols, well above 300 milliosmols).
  • To be absorbed, the concentrated solution must be held in the lumen of the intestinal tract until enough water can be secreted into the intestinal tract to dilute the concentrated milk replacer solution down to 300 milliosmols or below.
  • This can take considerable time and may stall out the intestines and can result in dehydration and the growth of pathogenic bacteria.

Can milk replacer and electrolytes be combined in one feeding?


  • Milk replacer should be mixed according to correct mixing directions and fed separate from electrolytes.
  • An electrolyte like Kentrol should be mixed according to its correct mixing directions and fed at least 30 minutes after the milk replacer feeding.
  • Combining both milk replacer and electrolytes into 2 quarts of water will produce a mixture that is high in osmolarity (500 milliosmols or higher) and will be held in to the lumen of the intestinal tract until water can be drawn into the gut to dilute the mixture.  This can actually increase the scours that may be occurring.

What occurs if calf milk replacer is mixed too diluted?

(Sometimes done to provide water in the same feeding so water does not have to be fed separately.)
The calf’s absorption and digestion processes work best if milk replacer is fed at recommended rates (260-280 milliosmols and then offered water about 30 minutes afterwards. If calf milk replacer is diluted more than labeled mixing directions (for example, 10 oz. in three quarts of water instead of two quarts), the resulting mix will be too diluted (less than 300 milliosmols) and will not be absorbed and digested as well.  Having access to water too soon will even further dilute the milk replacer and further reduce absorption and digestion. 

When is best time to provide water?

Ideally, water should be offered 30 minutes after milk replacer is fed for several reasons:

  • Milk replacer should be fed at 100ºF in order for the esophageal groove to close so milk goes directly to the abomasum instead of the rumen.
  • Allows time for the suckling and drinking reflex to subside.
  • Allows the initial digestive processes to begin.
  • Water can then pass into the rumen and does not dilute the processes in the abomasums.