Foals: There are two kind of Foals Black and Gray both takes only one day to harvest.
Horses: There are six types of horses Clydesdale,Forest,Autumn,Perchercon,Silver,Pinto all takes three days to harvest.
I would go with Foals because foals harvests in 1 day and horses harvests in 3 days but if you harvest foals for 3 days as compaired to horse you can gain more coins.
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