What is the best mouser cat breed?

There is no particular breed of cat that is better at mouse hunting than any other breed. It all depends on the personality of the cat.

Maine Coons were originally bred for hunting rodents. However, they are now very domesticated and no longer prized as mousers. Feral and partly feral cats seem to be the best at catching mice now. They are not so domesticated and still run on their hunting instincts. Female cats also tend to be better at capturing rodents. This might be because they still have the instincts to catch food to feed their kittens. A cat that is well fed will catch mice quicker according to Cat time.