The reason we record information on how animals perform, is so that we can identify and put a performance estimate (EBV or Estimated Breeding Value) on those parts of an animal (i.e. its genes), which are involved in transmitting production related performance to its progeny. Animals, which breed superior performing progeny, cannot be identified accurately by "eyeballing" them.
What you see in an animal (its phenotype) is a combination of:
1. Its genotype (the sequence of genes that make up the animal).
2. A number, of what are known as, environmental influences such as grass, sunlight, wind, rain, trace elements, drenches, parasites, sickness and social stress expressing themselves as muscle, fat, bone etc.
How an animal performs will depend very much upon the extent to which it is exposed to these influences. For example, how much grass it eats, the number of parasites it is exposed to and how many drenches it receives or whether certain trace elements are absent in its diet. While all these influences are constantly changing and hence affecting the performance of the animal, the animal's genotype (genetic makeup) remains the same.
"Animals do not pass on to their progeny the effects of the environment. Animals pass on their genes, which make up their genotype."
Therefore in selecting an animal, in the absence of any performance information, you can quite easily be misled by its size, simply because the animal may have had access to the most grass and not because it has the best genes for growth.
Effective performance recording involves keeping the influences of the environment the same for each animal while measuring its progress. This ensures that the difference in performance between animals can only be the result of the difference in their genetic makeup (genotype). With these genetic differences now isolated, estimates of how the animals are likely to breed (EBVs) can be made.
Some breeders who are sceptical about using EBVs to select animals, often place heavy emphasis on pedigrees. In doing so, they are linking pedigree information to performance, that is, they believe certain bloodlines perform better than others. You will note that on this matter, performance recording sceptics and believers agree.
Performance recording involves:
> Giving animals within a recorded group the same opportunity to perform.
> Taking various measurements on these animals.
> Using these measurements to produce EBVs, which are estimates of how these animals will perform as parents.