A hard luck farmer agrees to be part of a biological experiment which is supposed to make the cows grow faster. But it has an unforseen side-effect - the calves are born pregnant with these creatures that don't resemble bovines whatsoever. They are much more like the monsters from a 1980's Roger Corman produced movie.
These little monsters are also contagious. If they bite a human, the human's offspring will be infected/pregnant with the creatures. After the doctors are killed it's up to the farmer and two transients to stop the contagion. Of course, the woman is pregnant.
ISOLATION is a very grim, dark movie and one of the best horror films of 2007.