What to feed, when?

To make the most of your calf rearing operation you need to maximise weight gains efficiently throughout the 3 phases of development.

Liquid Feeding Phase

All nutrients are obtained from milk or milk replacer for about the first 3 weeks.

Transition Phase

Milk and starter rations contribute to meeting nutrient requirements. Feed starter ration as soon as possible. After 3 weeks the rumen will be developed enough for the ration to be contributing to the energy required for growth, but it will not be developed enough to digest pasture or hay. The calf can be weaned when it is consuming 800gm to 1kg of starter ration per day.

Ruminant Phase

Nutrients are derived from solid feeds through microbial fermentation in the rumen. By the time the calf is 12 weeks the rumen will be developed enough for the calf to thrive on pasture (or pasture based feeds) or grain.

Establishing how much energy your calves need is important

Often we feed our calves large quantities in order to achieve good weight gains. Although the calves are no doubt happy with this it does little for our bottom line!

A 40kg calf requires 6.8 Mega Joules of Metabolisable Energy (MJME) per day for maintenance in ambient conditions, and more in cold, draughty, or damp conditions when the calf will use energy for warmth.

Calves require 11.4 MJME to gain 1 kg of live weight. For a 40kg calf to gain 0.8kg per day it will require a minimum of 15.9 MJME (6.8 for maintenance plus 80% of 11.4MJME to gain .8kg). Simply put, a calf will need the equivalent of 5.3 litres of whole milk per day to gain 800 grams.



Calf live weight in kg 35 40 50 60 70 80 90 100
MJME required for maintenance 6.2 6.8 8.1 9.3 10.4 11.5 12.6 13.6
MJME required to gain 0.8kg/day 9.1 9.1 9.1 9.1 9.1 9.1 9.1 9.1
Total daily MJME required 15.3 15.9 17.2 18.4 19.5 20.6 21.7 22.7

Here are the approximate Mega Joules of Metabolisable Energy found in common calf rearing products:

  • Whole milk- 3 MJME per Litre
  • Colostrum- 3.4 MJME per Litre
  • Whole milk powder- 21.9 MJME per kilo
  • Starter ration- 11-13 MJME per kilo DM