A Terran pig
Pigs, also called hogs or swine, were Earth animals that was often associated with farming. They had the reputation of being dirty and eating anything.
In 2267, Sulu noted that the planet Omicron Ceti III had no cows or pigs. And not even a dog. (TOS: "This Side of Paradise")
The SS Mariposa took several pigs with them on their initial mission in 2123. By 2365, the Bringloidi colony that the USS Enterprise evacuated brought many pigs on board the ship. (TNG: "Up The Long Ladder")
Insults
Pigs have also worked their way into many slang sayings. Being called a "pig" or "swine" is an insult in many languages.
In 2268, to convey the fact that she did not like him, Elaan called Petri a "Troyian pig." (TOS: "Elaan of Troyius") The Nazi-influenced Ekosians referred to those they pursued as "Zeon pigs". (TOS: "Patterns of Force")
Doctor McCoy once used the phrase "in a pig's eye" to describe that he was being sarcastic and didn't, in fact, believe something. (TOS: "Amok Time")
When B'Elanna Torres first met Tom Paris, she thought he was an "arrogant, self-absorbed pig". Four years later, she said jokingly that he had changed into a "stubborn, domineering pig". (VOY: "Day of Honor")
Foods
Several Human foods are made from the meat of pigs, such as bacon and sausage.