MANUAL ON IMPROVED FEEDING OF DAIRY CATTLE BY ... - Gart

4.1 Protein
FIGURE 3: Chemical breakdown of a feed into its components
Proteins are composed of amino acids, which all contain Nitrogen (N).
Nitrogen is not present in carbohydrates or fat. Proteins are one of
the most important parts of a feed and form an essential nutrient. It is
continuously needed by animals for the development and maintenance
of their body and for the production of milk, etc. Moreover, a constant
supply is necessary for the animals to remain healthy.
Functions of proteins in the animal body
- Make up new tissues and muscles in the body
- Repair the loss of body tissues / healing
- Necessary for growth and development of the body
- Necessary for the production and functioning of enzymes and
hormones
- Necessary to produce milk of a good quality
- Necessary during pregnancy for the development of the unborn calf
- Hair, horn, hooves and feathers are composed of protein
- Assist in providing resistance against diseases
- Milk contains casein, what forms the basis of cheese making
- Excess protein gives energy to the body
Presence in feeds
Proteins are found in the soft and green parts of plants. In particular in
the leaves. When a plant grows older, it develops a strong stem and
becomes less leafy. That is why an older plant contains less proteins.
Most plants obtain the Nitrogen (N), which they require to form proteins,
through their roots from the soil. However, one group of plants, the
legumes, are able to utilize N from the air. For that reason leguminous
feeds always have a relatively high protein content.
The total protein content of a feed is expressed as crude protein.
11
Manual on improved feeding of Dairy Cattle by Smallholder Farmers