According to Seymour Hersh, dogs were not used simply to intimidate prisoners at Abu Ghraib, but were used to hurt them as well:

It was the Arab man leaning against bars, the prisoner naked, two dogs, two shepherds, remember, on each side of him. The New Yorker published it, a pretty large photograph. What we didn't publish was the sequence showed the dogs did bite the man -- pretty hard. A lot of blood.