Tests revealed the horse had a damaged digestive tract due to parasites which greatly affected its ability to absorb nutrients from food and resulted in its malnutrition.
Quinlan claimed he had tried every type of food and regularly drenched all horses on the property but no speciality feed product or drenching product was found on the day of the inspection.
Checks by Tauranga SPCA established that a vet did treat the horse the previous October for the leg wound which should have healed if treated appropriately.
Rachael Adams, the lawyer representing Tauranga SPCA free of charge, told Judge Peter Rollo that it was accepted this was not a case of deliberate neglect.
"But it was a serious lapse in judgment by Mr Quinlan in failing in his serious obligations to take the necessary steps to get veterinary attention for this animal to remedy the situation."
Quinlan's lawyer Kaye Davies said her client had intended training the horse for polo.
Judge Rollo said he accepted it was an out-of-character lapse for Quinlan and also acknowledged he had significant involvement in equine sports in Turangi and Taupo. "As World Cup-winning captain Richie McCaw is fond of saying Mr Quinlan, you are only as good as your last game and on this occasion you definitely dropped the ball."
Judge Rollo fined Quinlan $1000 which he ordered him to pay to Tauranga SPCA as well as $389.10 costs towards the prosecution.
Tauranga SPCA inspector Jason Blair was satisfied by the fine and costs imposed and hoped the case would serve as a wake-up call to all animal owners that failing to provide appropriate care could lead to prosecution. "Clearly we cannot prosecute everyone and try to educate people in the first instance but this was a case which we felt we had to no choice but to prosecute to send a deterrent message not just to Mr Quinlan but the rest of the Tauranga community," he said.