In many species used by mankind, breeding programs have a simple structure: e.g. dogs, horses and meat producing sheep and goats. In such programs an intense selection of males takes place, because you need a limited number of males to produce the next generation. Some selection in the females is practised, because you need a lot of them as dams to produce the next generation, but this selection is hardly effective. In these species the breeding animals(especially the females) are in the hands of individual owners which take their own decisions on selection and mating. As consequences breeding goals change too often and are not used steadily, recording of traits and pedigree is less complete, selection and mating can hardly be influenced. This results in a low genetic improvement rate over generations.
In these species herdbooks play a prominent role in the breeding program. They do the pedigree recording and set the rules for the characteristics of the males and females to be selected as parents for the next generation. The rules for the males are often very strict and only a limited amount is approved for breeding. Often a lot of emphasis in this approval is given to conformation. For the females the rules are very loose, disapproval of females is seldom practised.
In horse breeding a lot is done nowadays to professionalize the breeding program. A limited number of stallions in the breed is approved for breeding by the studbooks and females with the best conformation, health and performance traits are promoted for breeding. This results indeed in a genetic improvement that can be established in analyses.
In the breeding of dogs, shows play an important role in the selection of males. A limited number of males with the best conformation score at shows is used for breeding, often without any control by the breed association. Nowadays, dog breeding is under discussion in the society due to the negative side effects of a strong selection for conformation and the high relationship among animals in the population leading to inbreeding and the high frequency of genetic defects.
In meat producing sheep and goat breeds the selection of rams and bucks is most effective as you need a limited number of them to produce the next generation. Simple breeding goals for these species are weight and muscularity at a fixed age. With the use of young rams and bucks the generation interval can be kept short and creates genetic improvement. From a farm economics point of view, the ewes should produce litters as long as possible. So, the generation interval on the dam’s side is rather long. In more intense sheep and goat production systems fertile dam breeds are crossed with males from specialised meat breeds, resulting in a lot of lambs with a good growth and slaughter quality. The Dutch Texel breed is famous for these traits and is globally often used as a terminal sire line to produce crossbreds lams from females of local fertile breeds. In milk producing sheep and goat breeds, the selection of the dams of the males used for breeding is practised. Progeny testing of males is hardly performed due to a low percentage of milk sheep and milk goats in milk recording schemes. Up to now, little genetic improvement is obtained in milk sheep and goats.