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It must be emphasised that whole milk consists of two important types of proteins – caseins and whey proteins.

Caseins are the large protein complexes that form a curd and are needed to make cheese curds. Whey proteins, on the other hand, are small proteins in milk that are released in the whey during cheese making.

Types of CMR:

  • A WMP-based CMR, such as Ancalf, contains a nutrient profile almost identical to raw whole milk, containing both milk casein and milk whey protein. It has milk fat as the sole fat source – milk fat is the only fat that contains butyrate, which is important for rumen development.
  • A SMP-based CMR, contains the same milk proteins (casein and whey protein), but must have added fat, as SMP contains less than 1% milk fat. It is not uncommon to use a mixture of milk fat and cheaper plant oils for this added fat.
  • Whey-based CMR contain only whey proteins (no caseins) and is therefore non curding. The fat is usually a mixture of milk fat and cheaper plant oils.

Why is curding important?

The natural way a calf digests milk is by having it curd in the abomasum – the calf’s fourth stomach. When a calf drinks milk or milk replacer, it bypasses the rumen and enters the abomasum.

Here it is split into whey and casein which curds by natural rennet and enzymes.

Whey is a watery substance that is quickly passed through the intestines and digested whereas the curd is a solid, yoghurt-like substance that stays in the abomasum and is digested slowly over time.

Scientific research suggests that a curding milk replacer fed to calves less than 14 days old can;

  • Increase growth rates 
  • Develop insulating fat around the organs
  • Lower mortality rates in calves facing bacterial infection


(Information source: Beef+Lamb Research and Development, June 2012.)