After estimating the breeding values and predicting the influence of selection decisions on the genetic response to selection, we are ready for action: actual selection and mating of the animals! Like many aspects of animal breeding, mating can have a different effect on individual mating decisions as compared to the overall population. The breeding goal for the overall population may differ from the breeding goal of the individual breeder. However, to achieve genetic improvement at population level, it is essential that selection decisions are made at population level. Individual breeders, subsequently, can apply their selection criteria to select the mate for their animal from the selection candidates that have been identified at population level. Mate choice may depend on a number of aspects such as the intended use of the offspring, the quality (or lack of quality) of the female, the price of the desired mating, or the distance to the mate (in case of natural mating). The aim is to find a suitable mate and produce good offspring, given the limits that you set yourself with respect to mate choice. Mating decisions at the level of individual breeder may have consequences for the rate of inbreeding at population level. Because if your mate choice is the same as the mate choice of many other breeders, than the mate of your choice will have many offspring in the next generation, whereas others may have none. Desired mate choice at individual level and consequences of individual mate choices at population level, therefore, may conflict with each other.
In this chapter we will consider reasons for, and consequences of, mating decisions such as to compensate points of lesser quality in your female, or to achieve certain qualities in your offspring (e.g. colour). We will also discuss potential consequences of intensive use of popular sires on population level, and briefly about reasons for parentage testing.
A note: mating and single gene traits
Mating decisions may also be based on trying to create or avoid homozygosity. In the situation of recessive monogenetic disorders, for example, mating decisions will be aimed at avoiding the risk of homozygous recessive offspring. However, there are also monogenetic traits that have a desired effect. For example having horns or not in cattle, or to create a specific coat colour. More about that in the chapter about monogenetic inheritance.