Genetics is a fascinating subject. Aside from a risk of problematic recessive genes getting expressed in the offspring of father daughter crosses when the offspring ends up with a pair of the recessive genes which means at that point the genes then get expressed, you start to see other problems arise that become more prominent with successive generations. The case of the longhorn cattle mentioned above is a prime example. That being said, if you end up with an excellent heifer from the bull/daughter cross, which is highly possible, you might not want to be so quick to sell her because she is inbred. Breeding an animal like this to an unrelated bull - just the one breeding - will eliminate ALL, yes, ALL the inbredness that has occurred. The same would be for ANY generation level of inbredness. Consider for a moment what I mean by this. Say the inbred animal has 85% of its genes as homozygous (an extreme case of inbreeding). Evaluate for a second when you breed this animal to a totally unrelated animal. EVERY SINGLE PAIR of genes will each have 1 gene from the inbred animal and 1 gene from the totally unrelated animal. THE RESULTING ANIMAL IS NOT INBRED. An inbred animal by definition has some number of identical paired genes originating from the same individual in the animals heredity. The resulting animal has NO IDENTICAL PAIRS and is therefore NOT inbred. This being said, DON'T cross a bull with his granddaughter unless you are trying to accentuate a specific trait. The inbreeding risk at that point for problems is likely higher than you want to take unless, as I said, you are aiming for a specific trait and are willing to take that risk, and the consequences, when the risk comes to fruition.
