Scientific Eye – Reproduction & Genetics (a 19m video) and here is a 15m 25s video covering Variation, Selective Breeding & Classification from KS3 Bitesize:
What is Selective Breeding? – a 2m 30s video:
Super Cow Creators – these gigantic cows resemble bovine body-builders. See how breeders have achieved such amazing results (4m 44s).