page_title: Domestic pig
section_title: Nursing and suckling behaviour
hierarchical_section_title: Domestic pig / Behavior / Nursing and suckling behaviour
caption_attribution_description: English: Pig, Kilcullen
context_page_description: The domestic pig, often called swine, hog, or simply pig when there is no need to distinguish it from other pigs, is a large, domesticated, even-toed ungulate. It is variously considered a subspecies of the Eurasian boar or a distinct species. The domestic pig's head-plus-body length ranges from 0.9 to 1.8 m, and adult pigs typically weigh between 50 and 350 kg, with well-fed individuals often exceeding this weight range. The size and weight of hogs largely depends on their breed. Compared to other artiodactyls, a pig's head is relatively long, pointed, and free of warts. Most even-toed ungulates are herbivorous, but domestic pigs are omnivores, like their wild relative.
  When used as livestock, domestic pigs are farmed primarily for the consumption of their flesh, called pork. A group of pigs is called a passel, a team, or a sounder. The animal's bones, hide, and bristles are also used in products. Domestic pigs, especially miniature breeds, are kept as pets.
context_section_description: Pigs display complex nursing and suckling behaviour. Nursing occurs every 50–60 minutes, and the sow requires stimulation from piglets before milk let-down. Sensory inputs (vocalisation, odours from mammary and birth fluids and hair patterns of the sow) are particularly important immediately post-birth to facilitate teat location by the piglets. Initially, the piglets compete for position at the udder; then the piglets massage around their respective teats with their snouts, during which time the sow grunts at slow, regular intervals. Each series of grunts varies in frequency, tone and magnitude, indicating the stages of nursing to the piglets.
  The phase of competition for teats and of nosing the udder lasts for about one minute, and ends when milk flow begins. In the third phase, the piglets hold the teats in their mouths and suck with slow mouth movements (one per second), and the rate of the sow's grunting increases for approximately 20 seconds. The grunt peak in the third phase of suckling does not coincide with milk ejection, but rather the release of oxytocin from the pituitary into the bloodstream. Phase four coincides with the period of main milk flow (10–20 seconds) when the piglets suddenly withdraw slightly from the udder and start sucking with rapid mouth movements of about three per second. The sow grunts rapidly, lower in tone and often in quick runs of three or four, during this phase. Finally, the flow stops and so does the grunting of the sow. The piglets may then dart from teat to teat and recommence suckling with slow movements, or nosing the udder. Piglets massage and suckle the sow's teats after milk flow ceases as a way of letting the sow know their nutritional status. This helps her to regulate the amount of milk released from that teat in future sucklings. The more intense the post-feed massaging of a teat, the greater the future milk release from that teat will be.
caption: Sow with prominent nipples. Pigs typically have 12–14 nipples.
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