They are primarily used for two reasons:
- Source of meat
- Sacrifices for temples/shrines
Normally, you won't need to worry about the size of your pig herd, and you may in fact have to periodically slaughter them if they get to big.
Even if you don't slaughter the pigs, you still may face a decline in their population. If that is the case, there are a few ways to increase the pig population.
- Ernalda's Swine Blessing. Either sacrifice once a year to gain Ernalda's Swing Blessing, or build a temple/shrine permanently dedicated to this blessing.
- Create more Wildland. Pigs thrive best in the wildlands, and if you clear too much of it for farmland and pasture, then your pig herds will decrease. Reversing this allows more forest for the pigs to flourish in.
- Disband temples/shrines. Your temples and shrines require a certain amount of sacrifices each year, and this includes pigs. If you have a large number, you can either reduce the size of big temples, or disband them entirely. Of course, this means you lose the benefits of those temples/shrines as well.
- Performing herd rituals during Sacred Time. This will increase the fertility of your swine, creating more piglets. If you have a devotee of Uralda on the clan ring, you can spend more magic on herds during Sacred Time.
- Sacred Time Omen. If you are willing to use certain Cheats, you can gimmick around with the Sacred Time omens until you get this one: "They heard the sound of contented grunting, and said many piglets would be born this year."