At what age do Fila Brasileiro get into heat?

Female dogs typically become sexually mature (go into heat) at 5-12 months of age, but some giant breeds may take 18-24 months.

Why do you want to know?

Please tell me you aren't planning on breeding your dog!

... Just a note. Before anyone else tries to give me trouble for simply answering a question:

I don't recommend that you breed your dog. Asking a question such as this shows that you are not informed enough to take on the huge responsibility of properly caring for a litter of pups and their mother. Only an experienced breeder should take on such a thing. And as my personal stand only, there are too many unwanted dogs/cats in shelters and on the streets as it is. These animals are being euthanized because there aren't enough people to give them loving homes. There is no need to add to that problem... That said, you should have your dog spayed as soon as possible. Pets can be spayed/neutered as early as 12-16 weeks. Not only does this prevent unwanted litters, but a female going into heat each cycle is at risk of a serious condition called pyometra, an infection of the uterus, which requires immediate surgery and can be fatal. There are also studies that suggest an unaltered female can be at higher risk for cancer and tumors, especially of the mammary glands, and spaying early can prevent this.
Please always have your pets spayed or neutered!