Why do pigs produce less milk than cows?

Pigs don't produce milk in the same way that cows do. Cows are ruminant animals and have a specialized four-chambered stomach that allows them to break down plant material effectively. This enables them to digest large amounts of grass and other forages to extract nutrients, and consequently, produce milk. Conversely, pigs are omnivorous non-ruminant animals and do not have such specialized digestive systems. Although pigs can ingest plant materials like some of the feed they are given, these constitute only a part of their overall diet. Hence, their primary nutrient source differs from that of cows, so milk production is not prominent in pigs.