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Example: breeding limitations and rate of inbreeding in Friesian horses
The Friesian is a relatively large (i.e. in numbers) Dutch horse breed. However, it has not always been large. Originally it was used as farm horse in Friesland. During the week it was mainly used to pull farm equipment and on Sunday it was a used to show off when it pulled the ‘sjees’ (carriage) to church. In the 1950’s the tractor was gaining popularity and the Friesians, like other farm horses, were out of a job. The result was that the population decimated in size. In the 1980’s the Friesian became popular again as horse to be used in leisure sport (both in harness and under saddle). The increased popularity, in combination with the availability of AI, resulted in a rapid increase in population size based on relatively few stallions. The result was a rate of inbreeding in 2000 was 2%. There were signals of inbreeding depression like a reduction in semen quality and mare fertility. There was also an increase in frequency of genetic disorders such as cryptorchidism, placenta retention, dwarfism, and hydrocephalus. The breeding organization decided that action was required and in 2003 the number of breedings per male is limited to maximal 180 breedings per stallion per year for a maximum of 6 breeding seasons. From the age of 9 years onwards the limitations are removed. These breeding limitations have economic consequences, especially for the stallion owners, but are positive for the future perspectives of the population as a whole. In 2013 the rate of inbreeding was reduced to 0.5%.
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