It says in my cheese making book that you can only make cheese with milk from mammals.  But I know you cannot make cheese out of pig’s milk, (as you know, pigs are close to my heart) not that I would want to milk a pig.  I found an explanation: the short-chain fatty acids that provide the typical flavor to dairy products produced from ruminant milks (e.g. cow, goat, sheep, etc.) would not be present in pig milk. The fatty acid composition of the fat in the milk from pigs will be a function of the diet of the pig, just like it is for milk fat in human milk.  So, it would seem, it is to do with the short fatty chain acids needed for cheese making.

I came across a useful and interesting table that shows the % of fat, protein, lactose and ash in various sources of milk.