What are the dangers of cross breeding or inbreeding cattle?

It is FAR more dangerous to inbreed cattle than to crossbreed them. Inbreeding exposes genetic abnormalities that would only be exposed if a hetero cow was crossed with a hetero bull for a particular genetic abnormality. Inbreeding is only done if you are mating siblings, daughter to sire, son to dam, cousins, son to granddam, daughter to grandsire, etc. It can also kill your herd as far as productivity is concerned because the more you inbreed, the worse-quality your cattles' offspring will be.

Crossbreeding on the other hand, occurs when you breed a different breed a bull to a breed of cow: for instance, breeding a Black Angus bull to a Hereford cow. The offspring that comes with this cross is the exact opposite of inbreeding: you get a very vigorous, high-productive calf that will Excel above either of his parent's breeding in the feedlot or in the breeding herd. Generally cross-bred animals live longer and are much better-quality than those breeds that it came from. If you want a herd with great-quality cattle, use cross-breeding.