The cat might be fulfilling the dog's maternal instincts, but it would be best to put a stop to it now. Every time you see it happening, separate them.
You have a 7-year-old dog that is allowing a cat to nurse and appears to have milk. This is unusual but does occasionally happen. Your dog may be having a "false pregnancy". Some dogs will get a condition where they think (and their body responds) as though it is pregnant or nursing.
A kitten will need to be kept separate from an especially energetic dog until she is fully grown, and even then she should never be left alone with the dog. Usually, a well-socialized cat will be able to keep a puppy in its place, but some cats don't have enough confidence to do this.
Like with cats, separate your kitty and your dog for the first few days, keeping your kitten in their “safe zone” while the dog gets used to their kitty smells underneath the door. Once your dog is ready, allow them to see your kitty through a baby gate or other barrier.
Setting up a baby gate between the kitten-only room and the rest of the house allows your dog to interact safely with your kitten when you are not directly supervising. Make sure the baby gate doesn't have any spaces that your kitten can slip through.
Ensure your dog receives a lot of individual attention from you during the period of time over which you are introducing the kitten/cat. Do not leave your animals alone together until you are absolutely certain that they tolerate each other, the dog has been trained not to chase the kitten/cat and they are all safe.
The simple fact is that kittens play a lot, and this can sometimes trigger a dog's prey drive. It's better to err on the side of caution and take as long as you need. Eventually—especially once your kitten is a little older—your pets will be calm around each other. Over time, they could even become good friends.
Absolutely NO Alone Time
Never leave a dog and cat alone together until you are one hundred percent sure they are comfortable with each other. It is simply not wise to leave them unsupervised while they are still checking each other out. One animal or the other could be bitten, scratched, or worse.
Hissing, Barking, or Growling
A dog may bark at a new kitten that's hanging around the house. Other times, your pet may hiss or bark at you—particularly when you are giving your attention to the triggering object. Your quiet dog may suddenly start barking at you every time you pick up the baby.
While there are some parings that work out in days, in some rare cases, it never works out. Liz Palika noted that, in her experience, the "get acquainted" process usually takes two to three weeks. Dr. Landsberg noted that sometimes it's not easy to tell by their interactions if a dog and cat are getting along or not.
It's natural for your cat to be afraid of dogs, so don't worry if your kitty doesn't seem to be a fan of them.
Keep the first few sessions short and calm. Keep the dog on a leash and let the cat come and go as he wishes. Do not restrain either pet in your arms, as injury could result if either pet behaves aggressively. Ask the dog to sit and reward him with small tasty treats for calm behavior.
Once they have established that bond, the dog will take care of the kitten as part of its pack. Taking care of other species' young is not exclusive to dogs and cats. The instinct to protect their young is maternal, but the desire for companionship can come from any animal.
As soon as you notice signs of stress in your dog's body language, separate the cat from the dog immediately and give them time to calm down. Growling, stiff body posture, still eye glares, lip licking, and shaking are all warning signs that your dog could react in an aggressive manner.
A false pregnancy is a condition where a female dog exhibits various symptoms of pregnancy, such as producing milk and building a nest for her puppies, but is not pregnant. Female dogs can also produce milk when another creature, such as a puppy or kitten, sucks and kneads her mammary area, even though she may not be ...
Because kittens are small and want to run and play, dogs with a strong prey drive may be very excited by a kitten's movements. Even if your dog is OK with your adult cats, it is important to watch her closely when she's with a kitten.
Sometimes a cat and a dog will become instant friends, often they will develop a tolerance of each other over many years and occasionally they can't even be in the same room together. Just like with kids, sometimes a little bit of coaxing and a touch of manipulation is all that is needed to help them make friends.
In some cases, dogs will attack other pets such as cats if they feel threatened, and if they are too rough, they may even kill them.
Dogs often play by nibbling on each other's necks or mouthing each other's bodies. If your dog is nibbling on your cat in a gentle way and the cat doesn't seem to mind, then this is probably just rough play. However, if the nibbling is more aggressive or if the cat seems uncomfortable, it could be a sign of aggression.
Introduce Them Slowly
Setting them up in connected rooms with a baby gate between them can be an excellent start. When introducing your two pets this way, you should expect some excitement. It is okay if your kitten hisses and spits at your dog, they are just asserting their boundaries to a new creature.
(Kittens younger than four months should not be left alone for more than four hours. Older than that, they can handle another hour or so. When they reach six months, they can tolerate an eight-hour day without company.)
Plan to keep your kitten in their special room for at least the first 24 hours, and up to two weeks. This can be a great way to let them gradually get used to the smells and sounds of their new house. It's especially important if you already have pets in the house.
However, try to avoid exposing your pet to an unvaccinated animal, such as at the dog park. This is especially true with young animals because they are more vulnerable to infections than adults.
Cat-dog relationships can take weeks to fully develop. Whether it's new to the household or a longtime family member, a cat needs access to a dog-free sanctuary before they ever meet. Cat-dog relationships can take weeks to fully develop, which makes it a good idea to give your cat a safe place of their own.