Why is my 8-year-old spayed dog suddenly aggressive to other animals?

I strongly recommend that you have your dog examined by a vet since she is considered an old dog and very heavy and therefore could be suffering from painful arthritis which in turn may make her aggressive. If pain is the culprit, then NSAIDs given regularly will help control that pain and the aggression may stop. I would be worried that she will hurt your other pets and ultimately the humans in the house (not just your brother). Best keep her separated from the cats until you take her to the vet.

It could honestly be a lack of socialization to other animals from a young age. Puppies should start to be socialized young and if they are aggressive, should be put into training with a professional behavioral expert. It could also be related to hormones, as I see Destiny isn't spayed.

Hi and thanks for using Petco Pet Education Center, formerly Petcoach! Sorry to hear about Mylah and her apparent aggression. Aggression problems can be very complicated and complex. One thing you should do initially is take her to your veterinarian and let them make sure that she is healthy and that nothing appears wrong medically. Pain, etc can bring about aggression and irritability problems. Once the medical check is cleared, then you can discuss with your vet exactly what is going on behaviorally. Your veterinarian may want to refer you to a certified trainer or animal behaviorist to try to sort out what is triggering the aggression. I see she is spayed so we can rule out irritability/aggression associated with her heat cycles. I wish you the best of luck with little cutie Mylah.

I do not think it is anything you are specifically doing wrong. As dogs age they can have a change in personality but it is important to start training to turn this behavior around. IT sounds like she is scared and having some anxiety. I would recommend starting with basic commands like sit, stay and come. I also would recommend getting her in training classes so you can start to redirect her behavior. Once she starts feeling more confident it most likely will help with her behavior around other dogs. i hope that helps

The sudden temperament change can be due to stress from a new baby or maybe an indication of pain or a neurological problem such as tumor or dementia. You can talk with your vet about medicine for pain but with a new baby it is probably safest to not chance it and always keep them separate. If the medicines do not help and her behavior continues then I am afraid your only other option is considering euthanasia for everyone’s safety. I am so sorry you are faced with this!

Before assuming this is a behavior issue, I would want to rule out a possible medical issue first. When I hear about sudden changes resulting in aggressiveness, the possibility of pain or discomfort in one of the dogs could be the root of the problem. When a dog is not feeling well, it is only natural for it to react in a negative way if one of its buddies is trying to get it to act normally. A thorough physical exam should be performed by a veterinarian in order to rule out any sort of orthopedic or neurologic pain. Thyroid conditions can also be responsible for behavior changes as well. If it turns out that no medical issue can be be identified, you will have to start considering what may have started this sudden change of heart by Mill. You will have to think back to when it started, when the problem occurs most, where it occurs most, who is around when it is occurring, who ISN'T around when it is occurring, so on and so forth. These types of issues can be long and complicated to resolve, but usually as soon as the issue is identified the road forward becomes much easier.

Hi, thanks for using Petco Pet Education Center, formerly Petcoach! If this is a sudden behavioral change I would have her examined. She could be painful or not feel well and she is acting out because of that. It is better for her health to be spayed, she is at risk for an infected uterus which is an expensive surgical emergency. Hormones can affect temperament, so it MAY help but it might not be the solution. If her exam and blood work are normal, you can have her spayed then consider training and medications to control her aggression. I hope this helps and I wish you and Bella the very best!