Photo: Sabina Elvstål
How can this result be interpreted?
Well, first of all, there is no defined limit of an acceptable level of inbreeding in domestic animal populations. But generally, the following COI levels can be applied for the expected inbreeding effects:
COI < 5%: Significant detrimental effects are rare.
COI 5-10%: Modest detrimental effects on the offspring.
COI > 10%: Significant effects not just on the quality of the offspring, but there will also be detrimental effects on the breed (2).
Negative effects of inbreeding in horses have been reported in a number of studies. Even modest inbreeding levels (2-5%) are associated with lower percentages of motile and morphologically normal sperm (5). Increased inbreeding is also associated with decreased conception and foaling rates (6), early abortion frequency (7), and higher incidence of retained placenta (8). Inbreeding is often increased over time (1,9), and during the establishment of a new breed it could therefore be wise to keep inbreeding levels reasonably low, since the characteristics for future generations are set.
It should be noted that inbreeding may also have positive effects on the overall genetic value of a population (10).
The genetic diversity in the wild Kiger and Riddle Mountain herds have been analyzed periodically. The measured inbreeding related to the subpopulation varied over the years but was on average ≤ 3.4 % between 2003 and 2012 (11).