It's been a while since I read about this, but if I remember correctly, IQs lower than about 70 imply basically no language ability. The whole concept of IQ as a ratio between your mental age and your physical age is bogus, but yes, it's theoretically possible to define the IQ of a pig, or a dog or some other animal, through a series of problem-solving tests.
If I remember, your typical dog (or pig, which is pretty close) has an intelligence level approximate to a 2 year old human, of course without the language ability.