Beef, the meat of an adult (over 1 year) bovine, wasn't always as popular as it is today. America has had cattle since the mid-1500s, but most immigrants preferred either pork or chicken. Shortages of those two meats during the Civil War, however, suddenly made beef attractive and very much in demand. Today's beef comes from cows (females that have borne at least one calf), steers (males castrated when very young), heifers (females that have never borne a calf) and bulls under 2 years old. Baby beef is the lean, tender but not too flavorful meat of a 7- to 10-month-old calf. Meat packers can request and pay for their meat to be graded by the U. S. Department of Agriculture (USDA). The grading is based on three factors: conformation (the proportion of meat to bone), finish (proportion of fat to lean) and overall quality. Beginning with the best quality, the eight USDA grades for beef are Prime, Choice, Select, Standard, Commercial, Utility, Cutter and Canner. The meat's grade is stamped within a purple shield (a harmless vegetable dye is used for the ink) at regular intervals on the outside of each carcass. USDA Prime and the last three grades are rarely seen in retail outlets. Prime is usually reserved for fine restaurants and specialty butcher shops; the lower-quality grades are generally only used for sausages and in cured and canned meats. Ideally, beef is at its best — both in flavor and texture — at 18 to 24 months. The meat at that age is an even rosy-red color. If the animal is over 2 1/2 years old it is usually classified as "well-matured beef" and, though more full-flavored, the meat begins to toughen and darken to a purplish red. Slow, moist-heat cooking, however, will make it perfectly delicious. To store fresh beef: If the meat will be cooked within 6 hours of purchase, it may be left in its plastic-wrapped package. Otherwise, remove the packaging and either store unwrapped in the refrigerator's meat compartment or wrap loosely with waxed paper and keep in the coldest part of the refrigerator for up to 2 days for ground beef, 3 days for other cuts. The object is to let the air circulate and keep the meat's surface somewhat dry, thereby inhibiting rapid bacterial growth. Cooked meat should be wrapped airtight and stored in the refrigerator. Ground beef can be frozen, wrapped airtight, for up to 3 months, solid cuts up to 6 months. For questions on beef, call the USDA Meat and Poultry Hotline at 800-535-4555. See also baron; brains; brisket; chuck; club steak; delmonico steak; entrecôte; filet mignon; flanken; flank steak; heart; kidney; kobe beef; liver; london broil; minute steak; new york steak; noisette; porterhouse steak; pot roast; prime rib; rib; rib roast; rib steak; round; shank; shell steak; short loin; short ribs; sirloin; skirt steak; sweetbreads; T-bone steak; tongue; tripe; and veal.