In nature, the main force responsible for selection is the survival of the fittest in a particular environment. The wolves chase many sheep before they find one they can catch. Most of those killed by the wolves were weaker animals, and include those that were either very young or old. Thus, there was tendency for nature to select against the weaker ones and only the stronger survives to reproduce the species. So it is essential to have a look for the weaker and stronger in the populations because stronger individuals are responsible for making genetic structure of future populations.
Genetic properties of a population are expressible in the terms of gene frequencies and genotype frequencies. The value observed when character is measured on an individual is the phenotypic value of that individual.
Genotype is that part of genetics which is transmitted from one generation to next generation. Phenotype is the external appearance of the animal which is the sum total of genotype and environmental effects.
In practical conditions it is very difficult to separate environmental effects from real genetic worth. In these conditions real genetic worth of animals is become necessary to determine so that genetic improvement in a flock can be carried out. Large numbers of observations are required to determine real genetic potential of animal. There are some characters which are less influenced by environment and their value is almost accurate reflection of its genetic worth.
Inclusion of all non- genetic circumstances under the term environment means that the genotype and environment are by definition the only determinants of phenotypic value.
One must understand that there are some bad genes and some good genes in the populations. In simple terms we have to select good genes for propagation in coming generations while we have to block the bad genes in existing populations. In this way genetic structure of goat population will improve and its worth becomes more than previous generation. But how do we identify good and bad genes in the populations. I always emphasize that we should look at good characters which have higher economic value and left the remaining things. Bad genes here I refer to those genes which have no direct role in animal growth rather they degrade goat’s economic value.
Genetic structure of goat population in a flock could be improved by strategic breeding and marker assisted selection techniques. Prior breeding plans should be made with the help of previous experiences of other breeders in different species.
Genetic superiority is more important and of more concern because it is the genetic superiority which is transmitted. Therefore, the selection of superior animals will be effective to improve the progeny generation if their superiority is genetic rather than environmental. However environment is equally important for full expression of genetic characters, maximum development of characters of economic importance – growth, body form, milk production, litter size etc – cannot be achieved unless there are optimum conditions for nutrition and management. Different individual of the same flock might possess same genes but in essentially in different combinations. These particular combinations are called as genotypes.