There are many differing opinions and recommendations on the proper way of mixing a milk replacer. The need for hot, cold or lukewarm water and the effects on the calf are at the center of the discussion. Grober experience is derived from raising 70,000 calves annually. Research and information is compiled regularly related to feed costs, feed quality, digestibility, mixability etc. Changes are monitored at our calf rearing operations on a daily basis and throughout each growing period in terms of appetite and health for the calf and profitability for the operation. 

The rule is – milk replacers should be mixed in hot water. (70°C-80°C)

Animal’s Health or Farmer’s Convenience?

Every decision about milk replacer mixibility is really one of compromise. The balance between the animal’s best interest and the farmer’s convenience is always the center of the discussion. Technology is available to manufacture milk replacers that will mix in any situation – hot or cold. However, the best interest for the animal is achieved when the milk replacer is mixed in hot water. Factors include economy, fat dispersion and feeding temperature and each are related to digestion and profitability. 


Milk replacers are an expensive item when feeding calves (even though it is still cheaper to feed a milk replacer than whole milk). It is more costly to formulate and manufacture a milk replacer that has the feature to mix in cold water. Higher costs of added ingredients such as emulsifiers and special types of fats will increase the price.

Fat Dispersion and Mixing Temperature

Sourcing of high quality fats and the treatment of these fats is critical to successful digestion and growth. Equally important is the mixing temperature at the farm. Hot water affects the dispersion of the fat portion of the milk replacer. The fat will disperse more easily and completely in hot water than water at lower temperatures. Ideally, mix the powder in 45% of the necessary water at 70°C. Mix thoroughly and then add the remaining water to reach body temperature. (Remember that this mixture will cool down on it’s way to the calf and you should compensate your temperature accordingly so that the calf receives the milk at body temperature. Calf body temperature is 39°C.)


Fat Melting Point

The melting point if fat used in Grober Milk Replacers is 36 degrees C. If a farmer only calculates the mixing temperature by his ‘feel’, the temperature could be too low – imagine working outside on a cold day- tepid water will feel much warmer then a summer day. However the fat melting point remains at 36º. When the water is near this temperature, the fat will not mix. If fed to the calf it is likely to cause scours immediately.

Particle Size

Particle size and uniformity of the fat in the mix are factors for successful milk replacer feeding and for raising calves. Microscope photography provides an analysis of fat particles mixed at different temperatures. Mixtures that have been made as recommended -that is- mixing in hot water at least 70°C then adding cold water to achieve feeding temperature at 39°C, will have uniformity in the blend with fat particle size less than 1.5 microns.

Mixtures made at lower temperatures will result is varying sizes of fat particles- some as large as three microns and even some undispersed fats. The stomach enzymes will have more difficulty to digest these particles and will not provide the best growth. If sufficiently severe, stomach upset can result.

The use of hot water in the first step of mixing will ensure that the fat reaches it’s melting point and will disperse the fat evenly and completely in the water.

Fat Absorption and Feeding Temperatures for Milk Replacers

Feeding at less than body temperature affects absorption and digestion and ultimately the growth of the calf. Always mix in hot water first to achieve the best dispersion and then target the feeding temperature at the calf’s body temperature at 39°C.

When mixing the milk replacer at body temperature (or tepid water), the fat is not dispersed as completely nor as evenly. As well, by the time the bucket reaches the calf, the feeding temperature becomes lowered to less than desirable temperature. In these cases, the fat in the stomach will be digested more slowly and less completely as it passes through the various stages in the digestion process. Undigested fat in the small intestine will cause immediate scour problems. 

The stomach digestion needs to be as efficient as possible. Fat provides energy for maintenance and growth but as well fat storage just under the skin provides insulation. 
The feeding temperature of the milk replacer is important in ensuring that all of the fat in the milk replacer is digested by the calf. 

When a cold liquid is fed to a calf, it can lower the animal’s body temperature and the calf will utilize additional energy to generate heat to bring his temperature to normal. 
Even in summer, the same principle holds true. Feed milk replacer and additional water at body temperature instead of lower temperatures. The animal dissipates heat through breathing rather than sweat. Feeding water at cold temperature will cause a change in the stomach and will affect the digestion process.

What about Acidified Milk Replacers?

In applications where acidified milk replacers are available, the proper procedure still requires hot water mixing of the powder and subsequent chilling to reach the desired temperature.

The cold feeding of acidified milk replacers is done completely for the convenience of the farmer rather than the animal. Acidified milk replacers create a situation where other priorities can take up the farmers attention because the ‘calves are fed’. The most important key in dealing with calves is that the sooner you notice and deal with a potential health threat, the lower the incidents of severe problems. 

The use of acidifiers generally will increase the morbidity and cost to rearing calves. Profitability in a calf operation is directly related to the time spent with the calves.

Tools of the Trade

In an ideal situation, the best equipment to use for mixing your milk replacer is a mechanical system with a ½ horse motor, with a specially designed agitator and mix for three minutes.

However, this is not always possible. The next best solution is one that is the closest equivalent to the ideal. As an example, use a drill with a high rpm rating. At the very least, buy a heavy duty hand mixer and mix until your arm hurts. The aim is to get the best mix so that your calf gets all the best nutrition. Just for the record, a stick or simple hand swish is not sufficient. 

Calf rearing is challenging but the ideas suggested will result in improved growth and health.