Why whey

Why Whey?


There are essential differences in solubility, intake, digestibility (making use of nutrients) and consistency of quality when it comes to different milk replacers. Whilst much of the information below relates to calves, the principles apply to lambs and goat kids too.

These differences in calf milk replacer have a major impact on the health and growth of young calves. Whey-based milk replacers, like Sprayfo , will meet the energy requirements of growing calves, effectively boosting growth rates.


Whey is easy to digest

Quality whey-based calf milk replacers are easily digested in the gut, moving through the calf in only 2-3 hours, compared to 5-8 hours for traditional curding (casein) formulas.


Digestion of casein

  • Forms a curd in the abomasum - Needs approximately 7-8% casein to form a good curd – total volume
  • Takes 2-3 times longer to digest, so animal feels fuller for longer
  • Can restrict some animals concentrate intake, potentially slowing rumen development
  • Majority of calf milk replacers sold in NZ are casein-based (approx. 75%)



Digestive process for whey

Doesn’t form a curd in the abomasum

Digests 2-3 times faster, so animals are hungrier quicker and seek feed, ie. Concentrates

Aids in faster rumen development

Good quality whey-based products proven to help reduce incidence of nutritional scours too


  • Care needs to be taken not to over feed
  • Care needs to be taken when feeding directly off colostrum

Traditionally, most whey calf milk replacers weren’t recommended to be fed before 14-21 days. However, Sprayfo Blue Premium calf milk replacer can be fed to young calves directly from colostrum.

Whey is cost-effective

Because whey moves through an animal’s system in 2-3 hours, they will seek out concentrates (meal) sooner, enhancing growth rates.

  • Concentrates are obviously a more preferable, lower cost feed source for calf rearers.
  • Whey powder can also be mixed with whole milk (commonly known as fortifying), increasing its flexibility as a replacer.

Whey helps the weaning process

Animals reared on whey-based powders develop their rumen quicker, handling the transition through weaning with a reduced risk of the growth check common in stock reared on curding powder.

  • Early rumen development is essential for profitable animal rearing.
  • Rearers report less stress and continued strong growth rates, making for healthier, bigger, well-conditioned young stock.

Calf rumen development

Whey is safe to use

Good quality whey-based products can help reduce the incidence of nutritional scours.