Keep your lane position, and sound your horn while braking in a controlled manner. Sudden panic stops are not a good idea, as they could spook the animal, causing it to suddenly dart into the path of another vehicle.
DO NOT SLAM ON THE BRAKE AND DO NOT PANIC. Slamming on your brakes will cause you car to skid. Swerving is not the best option as you could lose control of the car and crash. So, slowing down and not panicking will leave you with the fewest injuries on your body. Your vehicle could be affecting depending on the animal. If you hit an animal, put your hazards on a call 911.