I am not sure what you mean. We are talking about thoroughbreds.
If there are any horses that Delaware permits to compete that are artificially inseminated they are Arabians, not Thoroughbreds. I have never seen an Arabian race outside of Delaware. From all I can tell, such races are only held in Delaware and Colorado in the US.
By definition, no Thoroughbred is the result of artificial insemination.
ML/NJ