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The nutritional requirements of animals

This material addresses aspects of the following syllabus outcomes:

H2.2 describes the inputs, processes and interactions of animal production systems.

The work presented in the following section contributes towards understanding the following syllabus content areas:

Students learn about:

Animal nutrition

Extract from Stage 6 Agriculture Syllabus NSW Board of Studies Amended 2009

Introduction

Animals in intensive livestock production systems require a diet which is balanced for the specific requirements of the animal. This means it needs to contain the correct proportions of:

In addition to these components, water must also be available.

Energy

An animal needs energy in its diet for several reasons:

The energy in a diet can be provided by many different components, but the feeds which supply energy in the greatest quantities are grains and fats or oils.

Ruminant animals cannot tolerate too much grain in a diet, as a condition called grain poisoning or acidosis can occur. The provision of high energy for ruminants must take this into account.

For more information about grain poisoning: http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0016/101338/grain-poisoning-of-cattle-and-sheep.pdf (external website)

Protein

Protein is the material which makes up muscle, skin, wool and most of the bodies of animals and needs to be provided in the diet of animals for them to make meat, milk and eggs.

Protein is made of chains of chemicals called amino acids, and in monogastric animals such as chickens, several specific amino acids called essential amino acids must be present in the diet. The most critical of these are Cystine and Methionine. Ruminant animals such as cattle do not have the same requirement of essential amino acids in the diet as the fermentation process in the rumen provides these to the animal.

High protein feeds are usually those which are called 'meals' and include by-products from the manufacture of other products. Examples of these are sunflower meal, meat meal, cottonseed meal. High protein feed are usually quite expensive and should not be provided to excess in a diet.

High producing animals need more protein in their diet than lower producing animals.

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Fibre

Fibre is needed in a diet to provide bulk as the food passes through the animal.

A ruminant animal (cattle, sheep, goats and deer) is able to ferment fibre and provide energy, but a monogastric animal such as a chicken or pig cannot ferment fibre for energy. The diets required by monogastric animals need more grain and less fibre than those for ruminants.

Vitamins and minerals

Minerals such as calcium and phosphorus must be present in the diet for the metabolic processes in the animal which require these. Vitamins are also necessary in the diet, ruminant animals have much lower dietary requirements for vitamins as many are synthesised in the rumen by the microbial fermentation process.

Formulating diets

Each type of animal has specific nutritional requirements which are based on the energy, protein, fibre, minerals and vitamin needs of that animal and also take into account the way the species digestive system uses the food.

Examples of the dietary requirements of some farm animals are:

The diet is formulated by mixing feedstuffs together to make a mixture which has energy, protein and other components in the correct ratios for the needs of the animal.

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Activity 1

  1. Use the diet calculator spreadsheet to formulate a diet for poultry.
  2. Which feedstuffs provided the most energy in your feed mix?
  3. Which components provided the protein in your diet?
  4. Which components of your diet only provided one nutrient?
  5. As you formulated a chicken diet, which component of the diet was easiest to get to the required (or target) level.
  6. As you changed the dietary mix, which nutrient was the most difficult to get into the correct level?

There are no absolutely right answers to these questions. You will need to play with the diet calculator spreadsheet to determine suitable answers.

Activity 2

  1. Use the diet calculator spreadsheet to formulate a diet for dairy cattle.
  2. Which feedstuffs provided the most energy?
  3. Which feedstuffs provided the protein in your feed mix?
  4. What was the total kg of feed in your diet?
  5. Is it reasonable to expect a dairy cow to eat this bulk of feed?
  6. There are many different diet formulations that will supply the needs of a dairy cow. What other factors would you need to consider to determine which was the best diet?

There are no absolutely right answers to these questions. You will need to play with the diet calculator spreadsheet to determine suitable answers.

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