Cows

I've been reading the Oracle 9i Complete Reference for work, and I came upon this example the author was gonna use to explain tree reports. The particular example the author used was a not a standard human family tree where branches don't cross or anything like that, no, he chooses a cow family tree. As I look at this cow family tree I notice a little bit of incest going on. The more I look at it, the more incest I see. One particular cow is the child of the same cow who was it's grandfather who was also it's great grand father. Something like this:

        |----------------------------
Barny The Bull ---|    \|/         \|/
Harpy The Hefer --|-->Nancy------> Betty -----> Jenny 

Is this normal? Are cows really inbred that much? I always thought there might be a little incest going on, but using the same bull again and again and again on the same line? What if cows are actually as smart as dolphins but they've been inbred so much that they're just stupid cattle?