Some breeding associations have regulations with respect to the mating intensity of the breeding males. Aim of these regulations is to control the genetic contributions of the males to the future generations, and thus the rate of inbreeding. To realize this they strive for equal contributions of each selected male. In general these breeding limitations are not appreciated by the breeders because their interest mainly lays in the short term result: they want to use the superior male for breeding or they want to earn money from selling matings. Those personal interests generally outweigh the long term interest of the entire population. People tend to believe the regulations are good to have, as long as they don’t influence their interest. Why should they restrict themselves where others were allowed to breed with that male? Why should they not be allowed to make money of selling breeding to earn back some of the costs they made for getting that approved male? You can imagine that this especially is an issue for species where males are privately owned, such as in dogs, horses, or sheep. In dairy cattle the males are owned by a limited number of AI service stations and they can sell semen from other males instead.
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 we signs 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 organisation 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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