Cow

Cows are passive mobs, they have brown skin with white spots, pink ears, grey horns, a white and grey nose with black nostrils, white scleras and black pupils. They are the only source of leather, raw beef, steak, and milk. They stand 1.6875 blocks tall, they're 0.625 blocks wide and 1.5 blocks long.

Uses
When killed, a cow drops 0-2 (97% Droprate) pieces of leather, as well as 1 - 3 (205% Droprate) raw beef. If a cow burns to death, steak is dropped instead of beef. Leather is used to craft the first tier of armor. Cows are usually necessary to make cake, as mooshrooms are the only other source of milk, and are much rarer. A cow can be milked by right clicking the cow with an empty bucket. A cow may be milked an unlimited number of times with one bucket. Due to the fact that cows can be bred an unlimited number of times using renewable wheat, all of the cow's products are renewable.

Behavior
Cows roam the Overworld in herds of 4 - 8 and can be observed jumping up slight inclines and falling to their deaths from tall cliffs and overhangs. Cows make no attempt to stay out of water, and will bob up and down to stay afloat. They will flee and jump around wildly if attacked. They tend to walk around, lowing (mooing). Cows are the biggest of the 5 animals(not counting mooshrooms because it is a variation of a cow or Villagers who aren't an animal). Cows will follow the Player when he is holding Wheat in his hand, and this can be used to lead cows to another location such as a pen for breeding or herding.

Breeding
All passive mobs (Excluding squid, ocelots, wolves and villagers) can be bred using Wheat.

Breeding will create a baby cow (calf) and the parent cows have a delay of five minutes in an actual day until they can breed again. Parent cows will follow the calf until it is full grown. There exists a bug with calves: if more than one calf is in an area, the parents can switch and/or just get confused and start to follow a calf that isn't theirs, or 4-6 cows will follow 1 calf and others are left behind, but they do grow up. Calves will not drop meat.

Creating a colony of cows and breeding them is a way to ensure that the player can get an unlimited supply of Steak, Milk and Leather when needed.

History
Cows were introduced in Alpha 1.0.8, dropping leather when killed and producing milk when the player used a bucket on a cow. This milk had no use until Beta 1.2, when Notch introduced the crafting recipe for cake that required 3 buckets of it.

As of Beta 1.8, cows flee and jump around wildly if attacked

As of Beta 1.9 Pre-release 3 Cow's milk also cures poison and all other potion effects.

Since 12w07b Cows have the new AI system. 

Trivia

 * Cows in the PC Gamer demo of Minecraft are branded with a 'PCG' logo on their side.
 * In SMP, clicking anywhere on the cow with a bucket will fill it with Milk, but only at the maximum distance at which you can use the bucket.
 * Because of the lack of hierarchy in every box model, the horns of the cow are sometimes misplaced. Jeb is planning to fix this.
 * In 1.8 cows seem to be less common than other passive mobs. This may be due to the fact that since 1.8 cows give an abundance of resources including beef, leather and milk whereas other passive mobs give less.
 * Because all cows in Minecraft have udders and are therefore female, all baby cows will have two mothers.
 * It takes one full minecraft day or 20 minutes for baby calves to become fully mature cows.
 * Calves will still give milk.
 * Cows can be an efficient mob since they drop Leather that can be made into armor and Raw Beef that can be eaten
 * Before Alpha 1.0.14, Cows were dark grey and had no horns.