According to Official Guinness Records,
The capital punishment of animals dates back to at least the early medieval period, with the earliest known documented case involving a pig tried and burnt for eating a child. The trial of the infanticidal pig took place in 1266 in Fontenay-aux-Roses, France, and was overseen by the monks of St Genevieve.
It was usually illegal to execute without trial in Medieval Europe, so everyone and anything would face a judge if suspected of a capital crime. Dogs, pigs, cows, horses and even bulls went to the stake or gallows, and were sometimes dressed in human clothes. Even corpses and inanimate objects faced execution.
For a complete list of 1266 records, please visit 1266 Guinness Records in France.