So the reasons why we don't drink pig milk or eat pig cheese are complicated. Clearly, cows, sheep, goats, all produce excellent milk and cheese. Even camels are milked.
But pigs are one of the exceptions to the farmyard milking rule. Pigs and horses and mice and dogs and cats all are not milked. Why? Well, let's just stick to pigs for now, because if we include all of those animals, I'd have to write a whole book.
So there are several important interconnecting factors to consider why determining why we don't drink Pig's milk.
1. The physiology of the pig itself
2. The creation of the pig as a domestic farm animal
3. The actual composition of pig milk
We do not know which of these factors are the most important, but all of them play a role in the pig not being used for milk.
1. The Physiology of the Pig.
Pigs are mammals, and thus they lactate to feed their young. However, unlike cows, sheep and goats, pigs to not have udders. In addition, pigs can have up to 18 piglets per litter, and thus they need a lot of nipples, each producing a small amount of milk.
The result of this is that it is very difficult to manually milk a pig. In fact, this would best be done by a machine that would hold the pig and reproduce the suckling actions of 14 simultaneous piglets. The complexity of making such a machine even today indicates that when humans were first domesticating pigs, they would have no way of effectively getting milk out of a pig.
This ties into:
2. The Creation of the Pig as a Domestic Animal
Pigs, like all farm animals, are modified forms of their wild ancestors. Thus, the purposes that the original domesticators of farm animals had in mind for farm animals were reinforced during the process of domestication. Thus, because pigs were difficult to milk, the domesticators of pigs did not breed pigs for the ability to milk them. Thus pigs remained difficult to milk and, in fact, have been bred to create more piglets and be even more difficult to milk.
This relationship between the traits of domesticated animals and the purposes humans have for them is fascinating and complicated and, of course, has to do with genetics and artificial selection.
Additionally, because the pig was bred as a meat animal, and pigs cannot get pregnant while lactating, farmers had every reason to stop the lactating of the sow as soon as the piglets were weaned so that it could begin creating a new litter. This resulted in another negative feedback against dairy production for domesticated porcines.
3. The composition of Pig's Milk
Chemically, pig's milk is richer in fat than cows, and so would be very nutritious for people to drink. It is actually more similar to human breast milk than other animals and so may have been preferable as a nutritious snack for children.
However, pig's milk does not contain the short-chain fatty acids that make goat, sheep and cow milk taste like milk. The long-chain fatty acids of pig milk would not taste bad, but they would taste strange to us. Additionally, the taste of an animal's milk is heavily influenced by the diet of pigs, and the diet of pigs varries significantly seasonally. Thus there would be no consistent flavor and sometimes it might even be objectionable.
Finally, we have a reason that I have not even listed. We do not drink pig's milk because we do not drink pig's milk.
It is perfectly possible now to create a machine that would milk a pig, a pig that would produce more milk, and even a pig that could get pregnant while lactating. But because pigs are not part of our cultural consciousness of the idea of dairy, and because they have an unclean image in the eyes of most cultures, it is unlikely that even if science can produce great pig milk that people will ever be interested in drinking it.
That is simply an effect of culture, which is far more complciated than anything silly, like the composition of fatty acid chains.
And now you know...or, more correctly, now you better understand how much we don't know about something so very simple.
- Hank Sock