Hog (animal)

I

Introduction

Hog (animal), domesticated mammal, of the swine family, extensively raised in almost every part of the world as a food animal. Hogs belong to the order of even-toed hoofed animals. They are further classified into the suborder of animals with 44 teeth, including two enlarged canines in each jaw that grow upward and outward to form tusks. The terms hog, swine, and pig are often used interchangeably for these animals.

Hogs are probably descended from two wild swine, one species from Europe and the other species from Southeast Asia; they were perhaps first domesticated in China about 9000 years ago, and later in Europe. They were introduced into the Americas by Christopher Columbus and the Spanish explorers, and present-day feral razorbacks are probably descended from those animals.

II

Characteristics

The adult domestic swine has a heavy, rounded body; a comparatively long, flexible snout; short legs with cloven hooves; and a short tail. The thick but sensitive skin is partly covered with coarse bristles and exhibits a wide range of color patterns. Like all swine, domestic hogs are quick-footed, intelligent animals.

Well adapted for the production of meat because they grow and mature rapidly, hogs have a short gestation period of about 114 days, and they produce large numbers of young each time they give birth. They are omnivorous and can scavenge a wide range of foods—perhaps one of the reasons they were first domesticated. As food sources, they convert cereal grains and legumes such as soybeans into meat. Other than meat, products from swine include leather (pigskin) for luggage and gloves, and bristles for brushes. For centuries they have also been used as a primary source of edible fat. In the United States until the mid-1920s, they were bred for the production of large amounts of lard. Swine in other countries such as England, however, were bred for the production of lean meat and were called bacon-type hogs. Modern swine are intermediate between these two types and are known as meat-type hogs. As the demand for fats has decreased, the meat-type hogs have been developed to resemble the bacon type more closely.

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III

Breeds

The types of hogs that have been bred reflect their major use. An estimated 90 breeds are recognized today, in addition to more than 200 varieties.

Eight major hog breeds are raised in the United States. The Berkshire (black with white points) and the Yorkshire (also called Large White) originated in England. The Chester White, Duroc (red), Hampshire (black with a white belt), Poland China (black with white points), and Spotted (black with white spots) originated in the United States. The Landrace, a large, long, white pig, was imported from Denmark. The major breeds also differ in growth rate, the number of young produced, mature body size, and ability to graze.

Most commercial hog production in the United States is based on crossbred animals, because crossbreeding results in hybrid vigor. The most used systems are two-breed and three-breed rotational crossing. In two-breed crossing, the sire of one breed is bred to the dam of another breed. The offspring of this cross is bred to a sire of the same breed as the dam in the first cross, and the offspring of this cross is then bred back to a sire of the same breed as the sire in the first cross.

IV

Production

Swine are reared under more intensive conditions than cattle and sheep. Such enterprises fall into three broad groups: production of purebred breeding stock, production of feeder pigs, and growing and finishing of feeder pigs for sale and slaughter. Some producers carry out all three activities, and recently many of them have formed cooperatives and built large farrowing units, where up to 1,000 sows can give birth. When the young feeder pigs are weaned at these large units, the individual members of these cooperatives buy them back for feeding and finishing.

Intensive production requires expert management and the cooperation of several different specialists, such as veterinarians and nutritionists. Feed costs account for about 75 percent of the total production costs, so careful selection of feeds for their nutritional adequacy and economy is important. Many other important elements must also be controlled when swine are raised under confined conditions. Newborn pigs are highly sensitive to cold. In addition, pigs have no sweat glands, so larger pigs must have facilities for keeping cool in warm environments. Proper ventilation also removes toxic gases, primarily hydrogen and ammonia from waste products. In addition, because the animals are confined in intensive production units, they must each be allotted a given amount of space. This ranges from about 0.3 sq m (about 3 sq ft) for each young pig to approximately 1.4 sq m (about 15 sq ft) for brood sows.

Under confinement, disease is controlled by vaccination, control of wildlife carriers of disease, antibiotics, and, in some cases, eradication of the disease-producing organisms. Compounds that can control the reproductive cycle, the length of the gestation period, and the timing of births have made it possible to control the breeding and farrowing so that a minimum of labor is required during weekends, when such labor is more expensive.