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2nd March 2021

Nutrition for Sheep 2: The Concepts of Sheep Nutrition


  1. The objectives of the sheep enterprise
  2. The concepts of sheep nutrition
  3. Feed intake
  4. Energy
  5. Protein
  6. Minerals & Vitamins
  7. Water
  8. Popular husbandry systems

2: The Concepts of Sheep Nutrition

The objective of this section is to provide more of an understanding of how we can produce rations which will not only satisfy the animals needs but also produce the best performance at the most efficient cost structure.

Fortunately there is now a whole range of books and computer software available, which contain lists, tables and equations telling us how much of each nutrient we will require to feed the particular animal we are trying to ration. So we don’t have to worry about calculating much of the information that we need.

Modern rationing is much more about knowing how to make sense of the computer generated gobbledygook that is often put in front of us, than actually having to work it all out. No, it is probably wise to get hold of a decent piece of software to do the spade work and learn how to interpret the result, or to discuss the customising of a professionally prepared diet to suit your own requirements.

The bad news is that in order to do this effectively, it is vital that there is a good understanding of what makes a good ration and equally, what makes a bad one. This means that we still need to have a good grasp of the principals involved in ruminant nutrition.

When considering the animal’s needs, the first thing to think about is “What is the food going to be used for?” It really is a very simple question but the answer provides all sorts of clues as to how to construct the diet needed.

Scientists refer to this question as “The partition of nutrients”. All this really means is, what does the animal do with its food?

All animals need food to maintain their body systems. Maintenance requirements are the nutrients that the animal needs just to keep itself running healthily and includes the energy needed to move about and keep warm.

Maintenance requirements are met before anything else can happen. The animal also uses food for growth (including laying down fat or condition), producing milk and pregnancy.

These four factors are very important and have to be considered individually when constructing rations.

For example, it might sound obvious, but it is no good building a list of requirements for a lactating sheep if we forget to add in the nutrients that she needs for growth in her late lactation. This is particularly important for gimmers finishing their first lactation.

Nutrient requirements are normally broken down into the following key elements:-

  • Dry Matter Intake (DMI)
  • Metabolisable Energy (ME)
  • Protein (ERDP, DUDP, MP)
  • Minerals & Vitamins
  • Water

These nutrient sources are normally sub divided into individual nutrient components.

For example, individual key minerals like calcium, phosphorous, magnesium; or energy sources like starch, sugar, and crude fibre etc, etc.

The animal’s requirements for each nutrient varies according to its level of production.

The most efficient way of feeding the animal is to supply it with exactly the right amount of each nutrient. This is unrealistic, so what happens in practice is that we supply the key nutrients like energy and protein as exactly as possible and then we try to get a “best fit” of all the others.

The use of powerful computer models has made the whole process a lot more effective than it used to be because the computer can simultaneously calculate all the nutrients required in the diet and find the best mix from the feed materials available.

The main pitfall with the computer is usually the operator! I frequently see examples of computer-generated diets that have been out dated by changes in the grass, silage or the flock lambing program; or they relied on inaccurate feed analysis or inappropriate production information. These diets tend to be way off the mark as far as accuracy is concerned and as a result tend to be expensive.

It is generally agreed that the best practise is to reassess the feeding regimes of all the livestock groups at least once a month.