Grass-fed cows wander slowly around the Farm and water Crops. They water Megacrops in the same time as they do regular crops, which take the player twice as long to water. This, along with the fact that they can keep crops watered and growing while the player is away from the farm, makes them incredibly useful.
Some items cause watered plants to drop items, such as Seeds or Fertilizer. If grass-fed cows receive these items, they will hold onto them and be marked by an exclamation point. Running into the grass-fed cow will pass the items onto the player.
Grass-fed cows can be bought, given, or rescued from Camps.
The second area of each Biome may have Camps containing grass-fed cows. One is the "Farm Animals" camp, where clearing the Enemies from the camp rewards the player with a choice between two farm animals. The other type is the "Corral" camp: clearing the enemies will grant the player all the animals inside the corral, which may include a grass-fed cow.
The Garden Shop in Town has a small chance to sell grass-fed cows in fall and winter, for 1600 or 2500 depending on the Season.
At Seasonal Festivals, the Rose Market also has a chance to sell grass-fed cows, in exchange for 4 . They are also a rare prize at the Seasonal Festival Casino.
Depending on the player's Yield Score at the Seasonal Festival, they may be awarded items. One of those items has a chance to be a Farm Animal, with a higher chance of gaining an upgraded Farm Animal in fall and winter.
If the player has the Glass Bottles upgrade, grass-fed cows can periodically produce Creamy Milk. These appear floating over the animal, and can be collected by walking into them or by using the harvest circle. Creamy milk sells for 90 each.
- Bubble Shield: Crops watered by grass-fed cows will produce a shield pickup, ready for the player to collect.
- Carrot Tractor: Energizes all friends when used, among other effects.
- Cattle Turret Tumors: Cows and grass-fed cows have Turrets on their backs.
- Doveotee: Animals cows and other friends become energised when the player uses a Scroll
- Disco Ball: Animals cows and other friends become energised whenever the player is.
- Fume Additive: Animals and other friends become energised when the player uses a Tractor
- Garden Cry: Animals and other friends become energised when the player takes damage.
- Glass Bottles: Cows and grass-fed cows produce Milk.
- Heart Beet Monitor: Animals and other friends are energised whenever the player is at low health.
- Laxative: Grass-fed cows and other farm animals periodically drop Fertilizer.
- Plastic Buckets: Cows and grass-fed cows move faster and hold more water.
- Soft Fur: Grass-fed cows and other farm animals become energised when the player walks into them.
- Straw Megaphone: Scarecrows can sometimes energize any animals or other friends close to them.
- Thankful Crops: Watered crops have a chance to drop seeds and fertilizer, which cows will pick up while working.
- Tough Hide: Cows and grass-fed cows block enemy bullets, and drop 1 Fertilizer per bullet blocked.
- Water Witching: Cows watering crops will zap nearby enemies for 50% of their health.
- Zealot: Animals and other friends may become energized when an Enemy is killed.