Conversation so far:
Are there any other interesting aspects about this article?
Outcross bloodlines can still be found.
How did imbreedng hurt the horses?
Statistical analysis has shown that inbreeding to Northern Dancer is on average slightly less effective.
were they breeding him with his chrildren?
his grandson Danehill sired 2,499 foals in 14 years at stud.
Was there any issues with the breeding?
inbreeding to a descendant such as Danzig is viewed as potentially problematic.
When did he retire from breeding?
CANNOTANSWER.

Question: How often was he bred?
Self-contained rewrite: How often was Northern Dancer bred?