Full Title Name:  Biological Information, Terminology and Hog Production Phases

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Leana E. Stormont Place of Publication:  Michigan State University College of Law Publish Year:  2003 Primary Citation:  Animal Legal and Historical Center

The article contains general biological information about hogs, farming production phases and commonly used terminology.



Pigs are omnivorous cloven-footed mammals, members of the family Suidae. Their bodies are characterized by long snouts, with heavy, sparsely bristled bodies, short legs and a small tail. In the United States, the term pig refers to young animals who have not yet reached market weight, while mature animals are referred to as swine or hogs.

It is believed that pigs were domesticated either in China or in the Middle East as early as 9,000 years ago and most domestic pigs are descended from the European wild boar. The species spread throughout the world traveling along wherever humans carried them. Columbus introduced pigs to the Americas on his second voyage in 1492 and more were shipped from England to colonists in Jamestown. Pigs are unique in that they are one of the only large mammal species that are found in some genetic variation all over the world.

Pigs have a reputation for being overweight, lazy and not particularly smart. Pigs are actually very intelligent creatures with a highly developed vocabulary of sounds and problem-solving abilities greater than a dog. Pigs are naturally very clean animals, preferring not to excrete near their living and eating areas, and only become overweight when overfed by their human caretakers. Pigs are often thought of as dirty animals because they wallow in mud. This behavior is due to the fact that pigs do not have sweat glands and thus are unable to sweat to regulate their body temperature. Wallowing in mud keeps pigs cool and protects their skin against sunburn   and bug bites. Pigs are also great swimmers and will swim to cool themselves down.

Pigs are curious animals and when given the opportunity spend much of their time exploring, foraging, and rooting in the soil. The pig’s snout is a very sensitive organ, with tactile reception comparable to that of a human hand. This, coupled with the pig’s highly developed sense of smell, allows the pig to use its snout to explore its environment and to find food beneath the surface of the ground. A pig’s sense of smell and capacity to unearth items in the soil has led to their use in France to find truffles and have been used by police to help search for drugs.

Pigs are highly social animals, often living in small groups of three to five adult sows and their young. Pigs living together form close social bonds and work cooperatively. Social interactions among pigs also include bodily contact and resting pigs often lie in close proximity to one another.

Pigs also communicate vocally and demonstrate a wide range of audible communications. Vocalization is part of the mating ritual between male and female pigs and piglets become acquainted with and learn to identify their mother’s voice because she “sings” to them while nursing.

Approximately 24 hours prior to giving birth, a pregnant sow will leave the group, hollow out a hole in the ground and will build a nest out of soft natural material so that she may give birth in privacy. She will stay will her babies at the nest site for approximately one week and then will return to the social group. Piglets are weaned at approximately three months of age and will continue to live in the group with their mother and the other sows.


Barrow: a male hog that has been castrated prior to the onset of sexual maturation

Boar : an uncastrated male hog used for breeding purposes

Farrow : used to describe the process of giving birth to piglets.

Farrow-to-finish: hog operations where piglets are farrowed, weaned and fed until they reach slaughter weight, typically 225-250 pounds.

Farow-to-feeder: hog operations where pigs are farrowed and sold after they have reached a weight of 30-80 pounds.

Feeder-to-finish : hog operations where weaned pigs are purchased from a separate operation and fed until they reach market weight.

Feeder pig: a weaned pig that weighs between 30-80 pounds.

Finish: the act of feeding a pig until it reaches market weight.

Gilt: a young female who will be used for breeding purposed who has not yet farrowed her first litter.

Nursing pig: a piglet that has not been weaned.

Sow: an adult female used for breeding that has farrowed at least one litter.

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