Why is my one cat trying to steal and nurse another cats kittens?

Our question this week was:

Dr. Debra – I have two adult sister cats that just have 5 kittens each within 2 days apart. One cat keeps taking her babies and putting them in the others cats box and tries to nurse all 10 kittens. Even though I continually separate them, should I be worried about this?

Rebecca Mendola


Hi – thanks for your email. You wrote that you have two adult sister cats that each had a litter within a couple days of each other and one is taking the kittens of the other and trying to nurse them.

There are a few concerns about this. First, the energy that it would require for her to nurse all 10 kittens would be great. This could cause an unnecessary drain on her.

Another concern would be that the risk of a condition called neonatal isoerythrolysis. Cats are born with natural antibodies against other blood types. For instance, type A cats are born with antibodies specifically made to destroy type B blood. The same occurs in type B blood. Type B blood has very strong anti-A antibodies, but type A has relatively weak anti-B antibodies. The anti-A antibodies in type B blood are so strong that even a small amount of type A blood given to a type B cat can result in serious illness and even death. No antibodies against other blood types are found in the very rare AB blood.

Neonatal isoerythrolysis occurs in kittens with type A blood born to type B queens. In the United States, the vast majority of cats are type A but about 5 percent of domestic shorthair cats are type B. Less than one percent are type AB. In the purebred population, certain breeds have a higher incidence of type B blood. The following is a list of breeds and the incidence of type B blood within their population in the United States. The incidence of type B blood varies in different parts of the world.

Type A kittens are born healthy and begin to nurse. Within the milk of their type B mother are antibodies specifically created to destroy type A blood. As the type A kitten nurses, he absorbs anti-A antibodies from his mother. These pass from the intestinal tract into the circulation and the red blood cells of the kitten are rapidly destroyed. This results in serious illness and death and most kittens die within the first 48 hours of life. The severity of signs depends on the number of antibodies ingested and varies from kitten to kitten. Even kittens that nurse for only a brief time may develop severe illness and die.

Since the cats are sister – this probably is not a problem.

What can you do? You can separate them and allow the mother cats to bond with their litters. Maybe even a week or so of bonding time will allow the mother and kittens time to recognize their own and keep them to themselves. However, in nature – it is not uncommon for kittens to nurse from other queens.

Best of luck!

Dr. Debra

Click here to see the full list of Ask Dr. Debra Questions and Answers!