The pig (or swine) is an even-toed, hoofed mammal raised globally for its meat. Biologically, the pig is a non-ruminant omnivore, possessing a single stomach and consuming both plant and animal matter. Unlike grazing animals, pigs cannot digest large amounts of fiber, which dictates their nutritional requirements. A pig’s specific diet is highly flexible and depends heavily on whether it is raised in a controlled agricultural setting or allowed to forage naturally.
Commercial and Farm Feeding Regimens
The feeding of domesticated pigs in modern agriculture is a highly controlled process aimed at optimizing growth and health through scientifically formulated diets. Commercial pig feed typically consists of corn and soybean meal. Corn serves as the primary source of energy, while soybean meal provides concentrated protein and essential amino acids. Other grains like wheat, barley, or sorghum may substitute corn, and canola meal can replace some soybean protein when regionally available.
Commercial operations utilize a strategy known as phase feeding, which tailors the nutrient composition of the diet to the pig’s specific life stage and growth goals. The Starter phase, given to young, newly weaned piglets, requires a highly palatable and digestible feed. These initial diets are complex, often containing specialized ingredients like fishmeal, spray-dried porcine plasma, and egg products to ensure a smooth transition from a milk-only diet.
As the animal grows, the diet shifts into the Grower and Finisher phases. The Grower diet supports rapid muscle development, while the Finisher diet, fed up to market weight, maximizes weight gain and fat deposition. These later-stage feeds are generally simpler, relying heavily on corn and soybean meal. Supplements are added to ensure a balanced intake of necessary minerals, vitamins, and amino acids like lysine.
The Pig’s Natural Omnivorous Diet
In non-commercial settings, such as with wild boars or feral hogs, the pig’s omnivorous nature allows for a highly varied and opportunistic diet. Their natural feeding behavior involves rooting, where they use strong snouts to dig into the ground. This action is primarily used to unearth subterranean food sources.
They consume various plant materials, including roots, rhizomes, bulbs, and tubers, which are found beneath the soil surface. Above ground, they actively seek out fruits, seeds, green plants, and mast, which includes hard nuts like acorns. Although their diet is predominantly plant-based, they regularly consume animal matter.
Invertebrates form a considerable portion of their intake, as they root for insects, earthworms, and grubs. They also opportunistically consume small vertebrates, bird eggs, and carrion. This ability to adapt their diet to whatever resources are seasonally available allows the species to thrive across a wide range of habitats.
Critical Foods and Substances to Avoid
Feeding pigs requires careful consideration of both toxicity and biosecurity to prevent disease introduction. One of the most significant prohibitions in many countries is the feeding of “swill,” which refers to any food waste that contains or has come into contact with meat or meat products from mammals or birds. This includes used cooking oil that has not been properly heat-treated.
The restriction on swill feeding is a public health measure to protect against the spread of highly contagious exotic diseases. Pathogens like the viruses responsible for African Swine Fever (ASF) and Foot-and-Mouth Disease (FMD) can survive in meat products and be transmitted to pigs through contaminated food waste. Even food that merely touched a prohibited substance, such as a plate scrap, is considered unsafe.
Beyond legal prohibitions, several substances pose a direct toxic risk to the animal. Mycotoxins, poisons produced by molds and fungi, can contaminate feed ingredients if they are stored improperly, leading to severe health issues. Certain plants and weeds, along with blue-green algae found in stagnant water, are also toxic and can cause acute poisoning. Therefore, a safe diet relies on commercially manufactured feed or clean, raw fruits and vegetables that have never contacted meat.