Apparently the Kindle page numbers here match up with the print version.
Chapter 20, p155 - Very vague description of a living thing, assumed to be animal, in a shed.
Chapter 25, p196 Strike briefly speaks to Plug's neighbour, no specific details but she says he was previously prosecuted for animal cruelty. Strike immediately calls the RSPCA.
Chapter 59, p429 - not actual animal cruelty, but Strike describes a dog as looking like "A fox that had been shoved into a tumble dryer" 
Chapter 70, p513 boy is seen injured, no details of how the injury took place but they assume dog and make the jump to dogfighting.
Chapter 77, p557-560 several descriptions of Plug's men with various dogs, being "dragged on a lead" and "forced into a van" but nothing more violent happens.
Chapter 79 is where the main scene happens. It's quite detailed. Could skip the whole chapter because it's the only thing that happens in this chapter.
Beginning of Chap 80 has Strike injured by one of the dogs and they discuss how they fought it off, some insinuation that he would have liked the dog to be injured in return, but nothing huge. Safe to resume about halfway down page 573 which is quite a nice Strike/Robin scene, worth reading.
Chapter 82, p584 - Some description of not-nice treatment
Chapter 90 - Strike sees Plug with a puppy (nothing happens to the puppy)
Chapter 97 p699 - More third hand description, not good.
Chapter 99, p712 - brief mention
Chapter 102, p730 - brief mention
Chapter 113, p807 - Description of last interaction between Plug and agency during which he stabs Shah, Plug is probably arrested (never mentioned again)
That's as much as I could find.