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Anatomy

Each recognized breed of goat has specific weight ranges, which vary from over 140 kg (300 lb) for bucks of larger breeds such as the Boer, to 20 to 27 kg (45 to 60 lb) for smaller goat does. Within each breed, different strains or bloodlines may have different recognized sizes. At the bottom of the size range are miniature breeds such as the African Pygmy, which stand 41 to 58 cm (16 to 23 in) at the shoulder as adults.

Most goats naturally have two horns, of various shapes and sizes depending on the breed. There have been incidents of polycerate goats (having as many as eight horns), although this is a genetic rarity thought to be inherited. Unlike cattle, goats have not been successfully bred to be reliably polled, as the genes determining sex and those determining horns are closely linked. Breeding together two genetically polled goats results in a high number of intersex individuals among the offspring, which are typically sterile. Their horns are made of living bone surrounded by keratin and other proteins, and are used for defense, dominance, territoriality, and thermoregulation. Both male and female goats may have beards, and many types of goat (most commonly dairy goats, dairy-cross Boers, and pygmy goats) may have wattles, one dangling from each side of the neck. Goats have horizontal, slit-shaped pupils. Because goats' irises are usually pale, their contrasting pupils are much more noticeable than in animals such as cattle, deer, most horses, and many sheep, whose similarly horizontal pupils blend into a dark iris and sclera. Goats have no tear ducts.

Goats are ruminants. They have a four-chambered stomach consisting of the rumen, the reticulum, the omasum, and the abomasum. As with other mammal ruminants, they are even-toed ungulates. The females have an udder consisting of two teats, in contrast to cattle, which have four teats. An exception to this is the Boer goat, which sometimes may have up to eight teats.

Goats expressing the tan pattern have coats pigmented completely with pheomelanin (tan/brown pigment). The allele which codes for this pattern is located at the agouti locus of the goat genome. It is completely dominant to all other alleles at this locus. There are multiple modifier genes which control how much tan pigment is actually expressed, so a tan-patterned goat can have a coat ranging from pure white to deep red.