Foods that give nitrogen must be chosen

To live, plants take out of the soil mineral salts (see Booklet No. 6, page 10) which contain nitrogen, phosphorus, potassium.

Different plants have different needs (see Booklet No. 6, page 14).

All plants do not have the same need of the same amount of mineral salts.

Animals too have different needs.

· They need food that gives them strength and energy; these are called energy foods.

For example: maize, cassava.

· They need food to make their muscles and their meat. These are nitrogenous foods, foods that contain nitrogen.

For example: oil cake.

Modern farmers put fertilizers on their fields. Fertilizers complete the plants' food.

Modern farmers who raise animals also complete the food of their animals by giving them, as well as energy foods, foods that contain nitrogen. These foods are called feed supplements.

With nitrogenous foods an animal grows better and produces plenty of meat.

Food rich in nitrogen is called a protein- rich food.

Feed supplements, like fertilizers (see Booklet No. 6, page 14), are costly.

A farmer must choose the right feed supplement.

Many experiments have made it possible to work out the amount of digestible proteins (nitrogen) which each food contains.

The foods which are richest in nitrogen are oil cake, meat meal and fish meal, and milk.

The amount of digestible protein (nitrogen) in 1 kg of food

In the same way as for fodder or feed units, tables have been made which show the amount of digestible protein in each food.

Other tables have been made which show the protein needs of each kind of animal.

Animals make good use of energy foods and body- building foods if they are given mineral salts and clean water at the same time.