The true value of correctly processing milk proteins in a calf milk replacer

Farmers put trust in the label on a bag of calf milk replacer (CMR), believing that higher percentages of crude protein will enable their calves to grow quicker, but the ingredients listed can be misleading.

Never assume that more protein is always better as the way in which milk-derived ingredients are processed has a huge impact on how nutritionally valuable they are to a calf.

Although a CMR contains 100% milk proteins, it is important to question how these proteins have been processed and their remaining value to the young calf.

Milk proteins contain many bioactive ingredients but these proteins are not available after processing at high temperatures because they become denatured, rendering them more or less useless to the calf.

Low-heat quality ingredients are desirable in a milk replacer as it means that all the useful components in these ingredients are retained intact and can be passed on to the calf (Zenker et al., 2020).

Video showing coagulation (clotting) test

The renin in the abomasum mixes with low-heat skim or cow’s milk, creating a curd that slowly breaks down casein proteins before they are fed into the small intestine.

If proteins have been subject to a medium or high heat, the curd will not form and that means less natural microflora, which makes it harder for the calf to digest the protein. As a consequence, the caseins will flow into the small intestine at a rapid rate, predisposing the calf to nutritional and infectious scour.

Farmers may believe they are feeding good quality skim milk powder and are at a loss to understand why they are experiencing cases of scour or looseness in their calves.

To add to an already complicated picture, the temperature in which milk proteins have been heated is not displayed on the label and can only be found by contacting a manufacturer directly. Generally, milk proteins processed at low heat are more expensive than medium or high heat alternatives.

There is no correlation between crude protein and calf health and performance. Heat treatment of milk and vegetable proteins during manufacture affects the digestibility of the amino acids available to the calf for growth and performance. A balanced and quality amino acid profile, rather than crude protein of milk, is the more important consideration when determining digestibility to the calf and subsequent performance.

Milk proteins

The four best milk proteins for correct amino acid profile for growth and development of baby calves are low-heat skim milk protein, buttermilk milk protein, whey milk protein and whey protein concentrate. Others are available, but these will have been subject to extra manufacturing processes and cannot always be used efficiently by the calf.

Whey milk protein is a good source of protein and sugar but it can also contain derivatives of other milk proteins that have been heavily manufactured, such as whey permeate or whey isolate. While whey permeate and isolate are cheap, these are poorly digested by calves due to the effects of manufacturing.

Calves need a milk replacer that coagulates to form a curd or a clot during digestion, enabling nutrients to be slowly released over time. The quality of the skim and buttermilk elements determines how slowly or quickly this happens. The curd or clot needs to form rapidly before too much of the milk replacer passes through the abomasum.

Slow-release protein from skim also traps fat, trace elements and vitamins for slow release, aiding their digestion. This is what farmers should look for on the ingredients label and discuss in more detail with their supplier.

In particular, look for the quality of the skim as this will affect the speed of clotting.

Vegetable protein

Crude protein in milk powders can also be derived from vegetable proteins such as hydrolysed wheat protein, pea flour and soya flour. Hydrolysed wheat protein is often considered as one of the better vegetable proteins. Others will contribute to the overall protein content but can cause anti-nutritional effects.

Conclusion

The best approach is to always use a milk powder with the highest milk protein that finances will allow, especially in the first four weeks of life. After 28 days, when the calf is physiologically starting to produce starch-digesting enzymes in abundance and is changing from a monogastric to a ruminant, vegetable proteins can be used.