Animals need energy to sustain life, move, grow and produce. This energy has to be supplied through feed. That is why, in assessing a feed, we look not only at protein and other nutrients, but also at the usable energy it provides.

What does metabolisable energy mean?

Not all the energy taken in with feed is used by the animal.

Part of the total energy a feed contains is lost in digestion and metabolism. The remaining energy that the animal can use in its metabolic activities is expressed as metabolisable energy.

Metabolisable energy is therefore one of the important indicators used to assess the usable energy a feed provides to the animal.

Why does energy matter in feeds?

The energy an animal takes in is used to sustain life, maintain body temperature, move, grow and produce.

If a feed’s energy value falls short of the animal’s needs, the animal may use the nutrients it takes in primarily to sustain its vital functions. This can affect growth or production such as milk, eggs and meat.

Meeting the animal’s energy needs is therefore one of the basic issues in feed formulation.

Which factors affect metabolisable energy?

The metabolisable energy value of a feed depends on the structure of the raw materials used and the feed’s total nutrient composition.

In particular:

  • the structure of the carbohydrates,
  • fat content,
  • protein content,
  • fibre level,
  • the digestibility of the raw materials

can affect the usable energy a feed provides.

For this reason, two different feeds with the same crude protein content may not have the same energy value.

The relationship between metabolisable energy and crude protein

Protein and energy are two basic elements that need to be assessed separately but are considered together in feed formulation.

It is not enough for an animal simply to receive enough protein. Protein, energy and other nutrients need to be in a balance that suits the animal’s needs.

For example, in a ration that is short of energy, the way the nutrients taken in are used may change. The goal in feed formulation is therefore not just to reach a high protein content, but to create the energy–protein balance the animal needs.

Does metabolisable energy vary by animal species?

Yes.

Different animal species have different energy needs and make use of feeds in different ways.

And even within the same species, age, live weight, growth period and production purpose can change energy needs.

For example, in broilers the need for energy and other nutrients changes with the growth period, while dairy cattle need a different nutrient balance according to the lactation period.

So when assessing the energy value of feeds, it is essential to take into account which animal and which production period the product will be used for.

Why does metabolisable energy matter in feed formulation?

When preparing a compound feed, different raw materials are combined in specific proportions.

The aim of the formulation is to provide the energy, protein, amino acids, minerals and other nutrients the animal needs in a suitable balance.

Metabolisable energy is one of the basic elements of this balance. If the energy target is not set correctly, other nutrients may not be used as intended either.

So when assessing a feed raw material, its energy value should be taken into account rather than looking only at its protein content.

Metabolisable energy in organic feeds

In organic feeds, too, meeting energy needs is one of the basic principles of feeding.

The organic production system may involve different requirements regarding the source of the raw materials used and production methods. But organic feed formulation also needs to meet the animal’s energy needs.

When assessing the raw materials used in organic feeds, therefore, both compliance with organic production conditions and nutritional and energy values are considered together.

Summary

Metabolisable energy is one of the basic indicators expressing the usable energy value of a feed for the animal.

In feed formulation, energy should be assessed together with crude protein, amino acids, minerals and other nutrients.

In correct feed formulation, the aim is not just to provide high energy or high protein, but to create a balanced nutrient structure suited to the animal species and production period.