From the very early days human beings depend on animals and animal products for food and other requirements. In dairy and poultry farms high yielding animals are reared. These high yielding animals are produced by hybridisation experiments. Previously the animals were developed basing on unscientific methods. Before the discovery of principles of heredity human beings have selected the animals with required characters and learned to develop the plants having the selected characters. This phenomenon is called Artificial selection
. However, an increased knowledge of biology, especially genetics, has helped in improving the quality of animals and animal products as per the human requirements.
ANIMAL BREEDING - PRINCIPLES
The animal breeder faces many complex problems during hybridisation experiments because many traits of animals are dependent on the interaction of multiple genes
. When the attempts are made only to increase the size of eggs in fowls,it was observed that the progeny produced yielded few number of eggs or even they die sometimes. That is if only one character is taken for improvement of the animals, the other characters will degenerate or result in harmful effects. Hence at the time of selection all the desirable characters are to be taken into consideration. The techniques for the improvement of animals involve principles of selection based on quantitative variations. It is not possible for all of the desirable traits to be obtained in one individual. The successful product must contain maximum number of desirable traits and a minimum number of undesirable traits.
1. The Body Form
It is an important factor in selecting racially improved variety of animals. A certain body form in cattle and broilers will be having high market value. They yield delicious mutton if they are having well built body form.
This is of great significance to the breeder. Some times it has first priority over other traits. For example the number of eggs, quantity of milk, or wool per animal is an important criterion in any programme of improvement of animals.
3. Quality of the Product
In addition to the quantity, the quality of the productivity is also to be taken into consideration during breeding experiments. The cattle which yield low quantity of milk but having high percentage of fat content are more prominent than those which yield high quantity of milk but with low percentage of fat content. Similarly he quality of wool in a sheep is more important than the quantity of wool.
4. Resistance to Diseases
The ability of the animal to resist diseases, to withstand adverse environmental conditions are also important in the animals produced by hybridisation experiments.
5. Early Maturity
It is another trait that the animal breeders look into for improvement of animals. The earlier, the animals mature to the productive age, lesser is the cost of maintaining them. If a hen matures early and begins egg production, it is more valuable than that which matures later.
6. Economy in the Use of Food
If the amount of food required to produce a certain quantity and quality of animal product is comparatively higher, the commercial value of such an animal is said to be very low.
In milk yielding cattle and egg yielding fowls if most of their food material is converted into productivity, such cattle and fowls are considered as more valuable. The above mentioned are only few of the desirable qualities that the animal breeders select for improvement of animals.