The maximum possible sentence for this offence is 6 months plus a fine
Animal cruelty (Revised 2017)
Animal Welfare Act 2006, s.4 (unnecessary suffering), s.8 (fighting etc), s.9 (breach of duty of person responsible for animal to ensure welfare)
Effective from: 24 April 2017
Triable only summarily
Maximum: Unlimited fine and/or 6 months
Offence range: Band A fine – 26 weeks’ custody
So he got near the maximum possible. If he had pleaded guilty that would have meant an automatic 1/3rd off the sentence, so 6 months becomes 4 months.