Oliver Smith "tore his arm apart" when a bicycle's brakes failed, causing him to crash into a window.
Two of the animals are due to be destroyed while a third has been kennelled as investigations continue.
Police said the case showed the age of an offender would not protect them from prosecution.
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Ned Eckersley's first-class best of 158 helps Leicestershire post 619 against Derbyshire as batsmen continue to dominate.
Listen to BBC local radio commentary as Derbyshire face Leicestershire in the County Championship.
Ashbourne News Telegraph
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