Trial compares performance of whey protein v whey powder

Using a whey protein-based milk replacer, over a whey powder-based alternative, could increase saleable milk yields by almost £500 a heifer.

This is according to research presented by Volac’s global technical manager, Ian Watson, and R&D manager, Dr Jessica Cooke, at the National Youngstock Conference in Devon (18 July).

While farmers will often look at the overall crude protein (CP) content when selecting a milk replacer, Ian said that it was worth going beyond protein levels and also looking at the raw material origins, as these can have an impact on the calf’s lifetime performance.

See also: How early life dairy calf nutrition affects long-term metabolism

As part of Volac’s Feed For Growth programme, a long-term, independent trial looking into the differences between forms of protein was conducted by The Agri-Food and Biosciences Institute in Northern Ireland, beginning in 2019.

Trial design

The study started with 14 newborn mixed-sex Holstein-Friesian calves, which were split into two treatment groups.

Each group was fed either a concentrated whey protein-based milk replacer or a whey powder-based milk replacer.

Both milks were equal in terms of their CP and fat content — 26% and 16%, respectively — and mixed at 150g/litre.

All calves were offered the same amount of milk for the first 56 days until weaning:

• Days 5-10 – 5 litres/day
• Days 11-34 – 7 litres/day
• Days 35-49 – 5 litres/day
• Days 50-55 – 2 litres/day.

Ad-lib starter feed, chopped straw and water were all available from birth.

Growth rates

Calves were monitored from birth, with the whey protein treatment group averaging a birthweight of 38.5kg and the whey powder group 39.7kg.

However, at the 56-day weaning weight, the calves fed on whey protein had overtaken the other group, weighing in at an average of 77.1kg, compared with 74.1kg.

“The calves that were being fed milk replacer based on concentrated whey protein were, on average, 4kg heavier [at weaning] and this is because [it] retains many of the naturally occurring bioactive components that are found in the whey fraction of whole milk and colostrum,” explained Jessica.

“These bioactive components are known to help support the health, and influence the health and development, of young calves.”

Age at first calving

The research team then wanted to see if this 4kg difference at weaning would make a difference to lifetime performance, so retained five heifers from the whey protein group and six from the whey powder treatment for further observation.

Although there was “not much difference between the two groups”, Jessica reported the group fed whey protein were slightly younger at first breeding – reaching the 400kg target at 445 days, compared with 450 days.

Subsequently, these animals had a greater proportion calving by 24 months: 80% compared with 33% in the whey powder group.

As well as this, the whey protein group had better fertility, with fewer services for each conception and a better conception rate (see “Volac calf trial – first calving figures”).

A greater age at first calving and more services have an economic impact, said Jessica, with the whey powder-fed heifers calculated to increase rearing costs by £63.14 a heifer because they were, on average, 22 days older at first calving.

This is based on £2.87/day for every day increase in age at first calving over 24 months, using AHDB Calf to Calving rearing costs, she explained.

Milk production

The heifers were followed through to their third calving, to evaluate if the milk replacer they drank as calves had had an impact on overall milk yields across their first and second lactations.

There were “similar numbers” surviving past 1.5 lactations between the two groups – an important parameter as this is when the payback of rearing costs is typically determined, said Jessica.

However, in terms of overall production, researchers found that days in-milk across the first two lactations were greater in the whey protein heifers – 658 days compared with 584 days.

What is more, milk yield for each day of life up to third calving was also higher in these heifers – an average of 12.6kg/day, compared with 12.1kg/day.

“Lifetime daily yield is a great parameter that actually indicates herd efficiency, because it incorporates the fertility, health, age at first calving and milk production of these animals.”

Again, Jessica pointed out that these differences had an economic impact. There was a total difference of 1,317kg in milk yield (in the first two lactations) between the groups.

Based on a milk price of 36p/litre, this equates to an additional £474 worth of milk in the tank from each heifer when fed a whey protein-based milk replacer as a calf (see “Volac calf trial – milk production figures”).

Not only is the financial outlook better, but improving lifetime daily yield is also beneficial to the environmental footprint of milk, she added: “That’s because if you increase lifetime daily yield, it reduces the emissions on a per kilo of milk basis.”

Not all protein is the same

Jessica said the study had proven that not all protein is the same and what is fed to youngstock can have a significant impact on lifetime performance.

“This not only has economic benefits but also a positive long-term environmental impact,” she said.

Ian encouraged farmers to look at the label on their milk replacer bag. “See what’s on there, see where the dairy ingredients are coming from, how many sources and what the quality is.

“If you’re in any doubt, ask your supplier. Labels can be a bit murky, but it’s important to know what they actually mean,” he said.