Principles of nutrition

When feed management decisions are being made, it is important to consider the composition and characteristics of different feeds, and the implications of including them into the farm system.

This section outlines the different components found in feed, what happens when a cow eats these & how they affect cow production & performance.

The six major components of feed: water, carbohydrate, protein, fat, vitamins, and minerals supply the animal with the water and nutrients needed for maintenance, milk production, reproduction, condition gain, activity, and growth.

Dry matter (DM)

Dry matter (DM) is the proportion of the feed remaining after all water has been removed and contains all the nutrients. The amount of DM is expressed as a percentage of the wet feed (% DM).

The major components of feed

Water	Dry Matter
	Energy			Vitamins	Minerals
	Carbohydrate	Fat	Protein

Energy

Energy in a feed indicates the feed’s ability to help the cow function optimally (e.g. maintenance, milk production, reproduction, condition gain, activity, and growth). Energy in the diet comes from carbohydrates, fats, and protein (when in surplus to protein requirements). Energy can be defined as gross, digestible, metabolisable, and net energy. Generally, in New Zealand, the energy available in a feed is expressed as metabolisable energy (ME) and is measured in megajoules (MJ ME/kg DM). If feed is analysed in laboratories in other countries, it is sometimes reported in megacalories (MCal/kg DM).

Learn more about the components in feed that provide energy in the pages below.