Little Albie suffered catastrophic head injuries in the horror at 39-year-old dad Neil Speakman's farm in Bury, Greater Manchester.
Albie stayed at Speakman's farm on alternate weekends after his mum and dad split up shortly after he was born.
While being interviewed by police, Speakman said: "[Albie] knew, he weren't stupid...it's a farm isn't it?.
The mum also said she was "so disappointed" in the verdict" after Speakman was cleared and claimed her little boy was "let down".
She said she had dropped Albie off at his dad's, who looked after him on alternate weekends, at around 9am.
