Feeding milk


3 min read

How often to feed calves? Is whole milk or milk replacer best? Choosing a milk replacer Choosing your method How to make raw milk safe for calves Advice for acidifying milk Additional resources

To ensure optimal growth, health, and well-being of calves, feeding strategies should be considered carefully. Recent research suggests that feeding a higher daily allowance, split into multiple feeds, is better for calves. When choosing between whole milk and milk replacer, both can be economical, but precautions should be taken. Selecting the best system for your farm will help reduce the stress of calf rearing, and ensure your calves get the best start to life.

How often to feed calves?

Feeding strategies should provide calves with enough energy for growth and play, ensuring they can mount a strong immune response, and also meet their behavioural needs.

Recent research shows that feeding calves once a day (OAD) for the first two to four weeks until they can digest solid feed, does not fully provide for their daily nutritional needs. Calves cannot consume enough milk in one sitting to meet their nutritional needs and will experience hunger. While they can tolerate OAD feeding, it’s not ideal for their welfare.

Feeding milk twice daily for two to four weeks, allows the calf to consume and digest adequate amounts of milk, and therefore energy, to maintain good health and growth. More energy also supports positive behaviour such as running and playing. Ad lib feeding systems also provide these benefits while conserving labour.

Some farms in New Zealand opt to use automated calf rearing systems, which allow the calf to choose when and how often they feed. This mimics the natural feeding behaviour of a calf on a cow. Properly managed, automated systems have been found to reduce nutritional or non-infectious scours and the need for additional labour.

The National Animal Welfare Advisory Committee (NAWAC) consulted on proposed changes for the Dairy Cattle Code of Welfare from April to June in 2022. In response to recent research, the Committee proposed that calves must be fed twice daily for the first three weeks.

It is unknown when the updated Dairy Cattle Code of Welfare will be released. Until then, the Dairy Cattle Code of Welfare (2019) remains in effect. Read more about DairyNZ's submission on the proposed Dairy Cattle Code of Welfare here:

Is whole milk or milk replacer best?

Calves can be reared economically on both whole milk or high quality, reputable milk replacers. In seasonal dairy systems there is often an abundance of surplus milk over spring, and many farms cannot justify the use of milk replacers on economic grounds.

Raw milk is a high-risk pathway for the spread of Mycoplasma Bovis (M. bovis) and certain other infectious diseases. Ensure any milk you sell or purchase is traceable by completing a feed declaration form.

There may be other drivers for farmers to use milk replacers, including:

  • Surplus milk is not readily available
  • Milk prices are high
  • Prevent infection from the herd
  • Control of diseases such as M. bovis and Johne's
  • Automated calf feeding systems

When choosing to use a milk replacer, calves need time to adapt to the new diet. This can be achieved by initially mixing replacer with colostrum/whole milk to let them adjust between the two feeds. Consistency is key to the success of milk replacers. Always read the label and mix according to the directions.

Automated calf feeding systems can achieve good results with milk replacers, as the preparation and mixing is consistent. Delivery to the calf and cleaning of the system is often easier and works better with freshly mixed milk powder.

Choosing a milk replacer

Protein and fat are two key components of your feed that should be considered when comparing milk replacers.


Protein content and source of protein in milk replacers can vary significantly. Calves respond best to dairy-based proteins compared to plant-based proteins. Not all milk replacers will state the protein source, so ensure that you use reputable products that have proven results when feeding young calves.

Calves will require around 22-25% of protein on a dry matter basis to support growth and development. The faster your growth plan, the higher the protein content required.


Milk replacers commonly provide less fat than whole milk, ranging between 18-22% on a dry matter basis. Higher fat products may be valuable under ad-lib, or high growth situations. Higher fat diets can also be beneficial to calves during colder conditions as they provide added energy.

Choosing your method

Whole Milk Milk Replacer

✅ Low cost

✅ No need to mix milk – can go directly from dairy shed to calf pens

✅ Contains a high level of fat and protein

❌ Storage of excess fresh milk can lead to contamination/reduced quality

❌ Risk of disease transfer between cow and calf

❌ Changes in consistency day to day based on cow diets & production levels

✅  Consistency of product – less risk of digestive upsets and scours

✅  Can be stored and handled more easily than fresh milk

✅ Not required to take any saleable milk out of the vat for calves

✅ Less risk of disease transfer from cow to calf

✅ Well suited to automated calf feeding systems

✅  Easier to achieve good biosecurity

❌ Cost compared to feeding unsaleable milk (e.g. colostrum)

❌ Labour required to mix 

❌ Need space & facilities for dry storage

❌ Risk of spoilage by rodents

How to make raw milk safe for calves

Feeding infected milk is high risk for spreading diseases such as M. bovis. Milk that has the lowest risk of containing M. bovis bacteria comes in these forms: calf milk replacer powder, acidified milk, or pasteurised milk.

If you’re feeding whole milk, consider the following:

  • Discard milk from cows under treatment for mastitis or other illnesses.
  • Aim for a pH level of 4.5 to reduce the risk of M. bovis. At a pH level of 4, the milk is unpalatable, and the calves will refuse to drink it.
  • Pasteurisation will kill M. bovis if the machine is working correctly and the proper procedures are followed.
  • Adding yoghurt to milk is a less reliable way to reduce the pH, as this process takes more time and is temperature, dependent to get the culture growing.
  • If the pH doesn’t drop below 5 for at least 8 hours, M. bovis will not be killed.
  • The addition of potassium sorbate preservative does not kill M. bovis.

Advice for acidifying milk

Do not acidify below pH 4 as this will result in thickened milk and risks complete coagulation. Calves will not drink milk with a pH of 4 or below.

  • Milk must be less than 24°C to minimise coagulation or clot formation.
  • Always add acid to milk, not milk to acid.
  • When using citric acid, the rate is 5.5g citric acid per litre of whole milk, or 550g per 100 litres of whole milk, or 5.5kg per 1,000L of whole milk. The acid needs to be sprinkled on top of the milk while it is being agitated.
  • Milk at pH 5 and below separates, but with gentle mixing goes back into a homogenous solution.
  • Gentle mixing of the milk twice a week is the recommended method. Continuous or vigorous mixing causes coagulation.
  • The target pH is 4.5 for a minimum of eight hours to kill M.bovis bacteria.
  • Test the pH of milk half an hour after the addition of citric acid and again just prior to it being fed to calves.
  • Use pH strips or an electronic pH meter. Note meters must be kept clean and calibrated when working with milk.
  • Systems that pipe milk may have coagulation in the pipes/tubes causing blockage of lines and nipples. This may result in the feeding of “whey” to calves.
Last updated: Jun 2024
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