Cow

Cows are a type of NPC animal found in The Sims 2 for Nintendo DS and PSP. Cows also appear as a part of the "Farm Fresh Folk Set" on The Sims 3 Store.

The Sims 2
Cows are featured in The Sims 2 for Nintendo DS. They are found in the field outside of Strangetown, near Jebidiah S. Jerky's home. They can be interacted with in three ways; Players can either milk them, or tip them over. They can also give the cow a gift, but only chocolate seems to have an effect. After the Sim has tipped the cow over, it will simply come back up. If a cow is milked after it has been tipped over it will produce a milkshake instead of a glass of milk. However, if the cow has been given chocolate it will produce chocolate milk, or chocolate milkshake (if it has been tipped over). This is only a feature and is profitable nor more effective in filling the need bar. In the field, there's also a red colored bull. No interactions are allowed with this animal.

Cows also appear in The Sims 2 for PlayStation Portable. They appear in the "Kine Dairy" building in Deadtree, but cannot be interacted with.

The Sims 3
Cows returned to The Sims 3 in the "Milkin' It Dairy Corral" premium content included in the "Farm Fresh Folk Set" from The Sims 3 Store. SimGuruTaterTot has shared some information about what this cow can do:

Abilities

 * Sims can milk cows to get milk.
 * Milk can fulfill Sim's hunger need.
 * Feeding the cow vegetables will make it produce soy milk, which will also revitalize the Sim's age (similar to Life fruit and ambrosia).
 * Feeding the cow chocolate will make it produce chocolate milk, which will also boost fun.
 * Sims can turn milk into cheese.
 * Sims can tip the cow and make it produce a milkshake.
 * Sims can play Tic Tac Hoove with a cow to increase the Logic skill.