Milk Guide Masterclass

3 April 2012

What is the difference between whole milk and milk replacers?

Casein (skim) content: The proteins which make up whole milk may, in simple terms be differentiated into casein (skim) and whey. The skim content of whole milk is approximately 80%. Due to the high skim content, whole milk will form a firm clot in the calf abomasum within 10 minutes of feeding, as a result of rennin, pepsin, and acid acting upon the casein. The clot is digested and empties from the abomasum into the small intestine for up to 24 hours.

Fat content: The fat content of whole milk is 33% dry matter, compared to that of milk replacers which is typically 16-20%. Milk replacers have been formulated with a lower fat content, to encourage higher dry feed intakes before weaning, which will help enable earlier weaning of the calf. Trials have shown that calves reared on milk replacer that consume more dry feed before weaning, will be heavier after weaning.  

What is the difference between whey and skim based milk replacers?

Clot formation: Whey based milk replacers will not form a clot in the abomasum, whereas skim based milk replacers will form a clot in the abomasum. The casein clot formation is however highly dependent on i) the quantity, and ii) the quality of skim in the milk replacer. If using a skim milk powder, it is essential that a firm clot forms – both the quantity and quality of the skim must therefore be high. A poorly formed, weak/loose clot can be detrimental to animal health as well as performance.  

Amino acid profile / protein composition: Whey is a key source of milk protein comprising a complex range of valuable proteins which are key for calf growth. Whey protein has a better amino acid profile than skim milk powder for growing calves. But it is essential to use a high quality whey based milk replacer that has been manufactured using low temperatures, since high temperatures during manufacture can damage these valuable proteins.  Both whey based, and skim based, milk replacers can contain vegetable proteins. Vegetable proteins are less digestible in the young calf, therefore the higher the level of milk protein (either whey or skim protein) the higher the digestibility.

Good quality whey based, and skim based, milk replacers have similar protein, oil and ash levels. If using a high quality whey based milk replacer, or a high quality skim based milk replacer (with a high skim content), there will be very little difference in the overall level of calf performance. Calves will digest the whey proteins as efficiently as skim proteins, although the whey proteins in milk do not clot. 

What should you look for when purchasing a milk replacer?

• Use a trusted supplier
• High quality milk protein: sufficient protein content (minimum of 20%)
• Low mineral content (ash content of <9%) and low pH
• If using a skim based milk replacer - check the skim content. This can be done by adding some vinegar or lemon juice to whole milk, and to the skim based milk replacer, and comparing the amount and size of clot formed.
• Above all, previous calf performance and calf bloom give the best guarantee for the quality of the milk replacer.

Regardless of type of milk:

Provide the calf with fresh, ad libitum water from about day 5: water is essential for dry feed intake, and rumen development. The rumen needs to be as well developed as possible at weaning, to ensure there are no set backs in growth post weaning when the calf must get all its energy and nutrients from the dry feed. A calf needs about 4L of water per 1 kg of dry feed.

Offer the calf high quality calf concentrate: ensure the dry feed is always fresh and palatable. Do not fill a trough with dry feed, as this will quickly become unpalatable to the young calf. Offering young calves small handfuls of dry feed daily, helps to ensure it is always fresh and palatable, which will encourage dry feed consumption.

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