How and why is the sentence '"The importance of keeping the pigs in good health was all too obvious" an example of Orwell's use of irony?=)

Another irony I find in the line is that, given the goals of socialism, the equality of all people (animals), there is absolutelly no reason why the health of pigs is any more important than the health of any of the other animals.  Of course, the irony is between what is said and what is meant.  This is a hint that the pigs are going to be something "special" on the farm, that the dream of the Old Major is going to come to naught, that the situation of the other animals will not improve, but only move from one sorry situation to another.