Why dairy goats? Unlike cattle, dairy goats are a manageable size. The largest animals, adult males ("bucks") may reach 200 pounds, but even mature females ("does") are likely to be closer to 100 - 140 pounds.These animals won't overwhelm their handlers or overburden the land.
Dairy sheep are scarce and expensive in the US, while serviceable milking goats can be bought for $300 to $500. Prices are higher for "show goats," which are bought for appearance qualities that score well in the show ring. Milkers can also command a premium price, depending on their bloodlines, while outstanding bucks can command very high prices, based on their potentially broad impact on herd quality and their resale value. Even so, dairy goats are far more reasonably priced than dairy sheep.
Goats and sheep prefer to eat in slightly different ways. In particular, goats enjoy "browsing"--eating leaves from shrubs and trees--while sheep are strictly grazers--eating grasses and similar plants. Faced with a green lawn bordered by leafy rose bushes, sheep will enjoy the lawn, while goats will stroll right over to the bushes. However, milkers are most productive on a diet of grain and hay, our own herd being very partial to alfalfa. Goats are also rather fond of poison ivy, privet and kudzu (a smothering vine with large leaves which grows rapidly here in the South)--a small herd of goats will happily keep kudzu in check.
US dairy farmers measure milk production in pounds, rather than in volume measures like gallons or liters. A gallon of goat milk weighs about 8 pounds, but the weight of a fluid gallon will vary from animal to animal, and even from occasion to occasion, depending on the concentration of solids, like milk fat, in the milk. In our herd, we expect even our less productive does to approach 8 pounds--or about a gallon--per day, although a good deal of that may go into their "kids" (offspring). The "stars" of our herd will approach 16 pounds--or about 2 gallons--per day.
There are six breeds of dairy goats which are raised commercially in the US, as well as cross-breeds (called "recorded grades"). Popular breeds include Saanen, Nubian, Toggenburg, Alpine, Oberhasli and La Mancha. These breeeds are typically distinguished by appearance, by productivity, and, some say, by temperament. Most of our goats are Saanens, which are distinguished by white coats, erect ears, sweet personalities, and good milk yield. Some Saanen develop "color"--shades of brown, black and grey. Such goats are sometimes labeled "Sable Saanen." Color is a recessive among Saanens, so Sables can have all-white kids, and white adults can produce Sable kids.
Other goat breeds typically include a mix of coat colors. Toggenberg, Oberhasli amd Alpine goats are similar to Saanens, except for the variety in coat color. Nubian goats have more bulbous noses, and, unlike these other breeds, ears that are pendulous rather than erect. We've known enough hostile, aggressive Nubian goats to suspect that this is a breed trait.
Perhaps the most distinctive appearance belongs to the La Mancha. Unlike the tall, erect ears of most breeds or the pendulous ears of Nubians, La Manchas have tiny "elf ears." Visitors to state fairs tend to believe that these goats' ears are bobbed, but the tiny ears really are genetic.
There is a good deal of information about dairy goats online. A quick search of the Web will turn up thousands of dairy goat sites. Just a few are listed here. Remember that perspectives on dairy goats vary by region in the U.S. For example, coccidia is not a problem for adult goats in the cooler climates of the Northeast and Midwest, but can be a problem in the Southeast, where winters are too mild to keep the microorganism in check.
Good Starting Points
The Georgia Dairy Goat Breeders Association (http://www.georgiagoat.com/) is a local ADGA affiliate.
The American Dairy Goat Association (ADGA) is the primary national organization for dairy goat breeders.
The Dairy Goat Journal is a very nice monthly.
Langston University is a leading goat research center in the U.S.
The Goat Community Web Ring lists 300+ goat-related sites. A favorite of ours is Jonathan Ballard's "Goats Rule!" site.
(The Dairy Goat Journal, cited above, is another source for books on goats.)
The New Goat Handbook is a nice little paperback.
.Goat Medicine is co-authored by Dr. Mary Smith, arguably the country's leading authority on the topic. Keep in mind, though, that Dr. Smith is based in New York. If you operate in a different locale, your experience may differ.