Short answer: the Pig earns the most by far: about 1,875g a day in Truffles on days it can go outside (not in Winter or rain), and more as Truffle Oil. Among animals that work every day, Sheep is best when you process the products with Artisan (562g a day), while a Cow earns 330g a day selling milk and pays for itself fastest. All at full hearts and mood, without professions unless stated.
Pick an animal and your farm's situation to see what it makes per day.
Results
Every animal compared
One animal each, with your hearts, mood, machines and professions above.
How the numbers are worked out
- Quality: score = hearts ÷ 1000 − (1 − mood ÷ 225), plus 0.333 with Coopmaster (coop animals) or Shepherd (barn animals). Iridium needs a score of 0.95 or more; then gold and silver are rolled, as the wiki describes.
- Large and Deluxe products: Large Eggs and Milk need 200+ friendship; the chance is (friendship + mood × mood modifier) ÷ 1200. Duck Feathers use ÷ 4750 and Rabbit's Feet ÷ 5000, plus daily luck (taken as 0).
- Pigs: one Truffle a day outside, plus extra Truffles with a chance of friendship ÷ 1500 each time (about 3 a day at full hearts). Truffle quality comes from your Foraging skill, so it is counted as regular.
- Machines: a product goes into its machine only when that is worth more. Large Eggs and Milk make gold-quality Mayonnaise and Cheese; good Wool can make a second Cloth.
- Professions: Rancher raises raw animal products and Artisan raises artisan goods. Truffles get neither (Truffle Oil gets Artisan).
Assumptions
- Hearts and mood stay the same for the days you enter. Mood depends on feeding, petting and the heater.
- Animals are already grown, and their house and the animal's price are not counted in the daily gold.