Why genetic diversity is important
One way to look at the loss of genetic diversity is as a series of funnels. Every time a group of animals is selected by humans for certain traits and abilities, that population becomes both filtered and reduced. This inevitably leads to a decrease in genetic variety and an increase of genetic risk. Genetic risks associated with low heterozygosity include inherited diseases, shorter life spans, limited growth, and a higher rate of offspring mortality.
Unfortunately the genetic diversity of the Abyssinian breed is rather low (28.7) see figure below from MyCat DNA, which means that if you want to improve the breed you need to work towards improving the genetic diversity of the breed.