From which animals phenotypes should be recorded, depends heavily on traits the characteristics of the trait: growth can be measured in males and females from birth to death; milk production can only be measured in females after the first delivery of progeny; eggs can be counted after the start of the laying period. Carcass traits will be known after slaughter. Disease resistance is only expressed in the presence of pathogens. Longevity can be fully established at the end of life of an animal. Therefore for categories of traits different sources of information are used to get an impression of the genotype of the animal to be considered for selection. These sources of information are informative because they are related to the animal under consideration.
Parents (pedigree) information: milk production, fertility, longevity
Sibs or half-sib (brothers and sisters) information: milk production, carcass traits, fertility, longevity or disease challenge
Progeny: milk production, carcass traits, fertility, health
Recording of traits cannot be done without costs. In dogs and horses, for example, you have to organize shows resulting in costs because inspectors have to be hired. In other species farms have to be visited by inspectors to assess the conformation of animals. For other species costly machines have to be bought to scan live animals or to record automatically important traits in slaughter houses. Low-cost methods facilitate recording traits on a large number of animals, but in case of high costs, e.g. ultrasound scanning of live animals, only animals with a high impact in a breeding program will be scanned.
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