So, to start off we recently adopted(about 4 days ago) two Great Danes(came as a pair) who are approximately 3 and 4 years old. One is male-Zeus, the other female-Mila. We already have two other dogs-one male and one female who we have had since they were puppies. We also have cats at home, all of whome are completely comfortable around dogs because everyone has always been raised together, and rule of thumb is everyone must get along, lol. Well, we adopted these two Great Danes and the owners had told us that they didn't have much time for them anymore and so we knew we were in for some obedience issues from the beginning. To what extent, well we weren't sure. In the first few days they have been fine with our other dogs, after slow introductions and taking everything one step at a time. They even got along with the cats and the female was sleeping next to them on the couch. Now all of a sudden today she has went after 3 of our cats, getting 2 of them and picking them up in her mouth and thrashing them around. Thankfully we caught her in time as it was happening and the cats are ok, although quite shaken up. These are big dogs, I can't afford to have them all of a sudden decide that they are going to dislike cats. In all of the situations Mila went to the cat, the cat was not running, darting, moving suddenly, etc. I hate to get rid of the dogs, and am hoping to find a quick fix to this. They could be great dogs with consistent training, but this is an immediate needed fix as it is life threatening and we have no way of keeping our cats away from the dogs all the time. Any advice, insight, tips, or personal experience with this would be great. If you need any more info, just let us know. I'm looking to get this resolved as quickly as possible as I cannot tell when she will again do this out of the blue. She's also the gentle one of the two Great Danes. When we go to the park they both show aggression towards other dogs, but at our house with the way we have introduced them we haven't had any problems. Thanks in advance!