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title: "1.13.2 Negative effects of selection for performance (2024)"
canonical: "https://wiki.groenkennisnet.nl/space/TAB/288391353/1.13.2%20Negative%20effects%20of%20selection%20for%20performance%20(2024)"
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It is not just dogs where we have taken selective breeding a step too far. Selection for large offspring has resulted in a high fraction of difficult births, sometimes requiring caesarean sections in the Texel sheep, and it was even a standard way of delivering in the beef cattle breeds Belgian White-and-Blue cattle and the Dutch Improved Red-and-White. In the Texel sheep selection against difficult births has resulted in a decreasing fraction of birth requiring assistance. In this case the process could be reversed. But in the Belgian White-and- Blue and the Dutch Improved Red-and-White cattle the situation is more complex and the repair process will take many generations.

Birth problems are not the only unintended negative consequence of selective breeding in farm animals. Remember that the intention was to produce a lot of food, but cheaply so that it would be available for everyone. This has resulted in intensive farming systems, such as in pigs and poultry farming, where the animal products should be produced with as little costs as possible. So fast growth or more eggs with less feed. This has gone very well for many years and breeders really thought that there would be no limits to the genetic improvements as production increased linearly. Unfortunately, in the 1980’s it became more clear that there were also some negative consequences of strong selection for performance traits. For example, broilers started to show metabolic health problems due to the fast growth, laying hens started to have increased bone fractures because they couldn’t manage sufficient calcium intake to deposit into the increasing number of eggs. However, in animal breeding the awareness raised that these negative effects should be corrected and avoided in the future. The introduction DNA techniques in animal breeding and the increased capacity of computers facilitates a more balanced improvement of desired traits and the avoidance of negative effects.

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