About the property, the remains of 32 horses were scattered.
"This case was distressing beyond measure," said RSPCA inspector Kirsty Hampton.
"What we were confronted with on arrival at the farm was grotesque," she said. "To see so many animals in such awful condition was overwhelming and those that had survived were shown little care or consideration.
"Many horses and ponies had just been left to starve, and the smell of rotting flesh was overpowering," she said.
World Horse Welfare field officer Nick White was one of the first at the scene in January 2008 and will never forget what he saw.
"After seeing the conditions in the fields, it wasn't until I went into the yard that the enormity of it hit me ... there were dead horses on the ground in front of me, and to the right.
"I looked across there was a dead horse in the stalls. It was like walking into another world.
"There were none of the normal noises I associate with a stable yard - horses moving about, eating, drinking, calling out to one another or the gentle noises that horses make when approached, expecting to be fed or cared for.
"They were totally silent. Even the horses that appeared in better bodily condition seemed to be depressed, almost as if they had lost their dignity."
The rescue unfolded over several days as animal welfare groups removed 111 horses from the farm, run by the horse-trading Gray family, who were sentenced early today (New Zealand time).
"Many people will think that no sentence can do justice to the cruelty the Grays inflicted on their horses," said World Horse Welfare chief executive Roly Owers, "but this is the most high profile test of new legislation under the Animal Welfare Act 2006 and it sends a clear warning message that neglecting and mistreating horses in this way is totally unacceptable and should always carry a heavy punishment."
Owers said the charity was pleased that justice had prevailed and James Gray has not only been given a 24-week jail sentence, but banned from owning and keeping horses for life.
"We are also very relieved that the rest of the family have been given 10-year bans as it will prevent more horses from suffering in their care for a considerable time, but it is essential that the bans are properly enforced."
Owers said the 11 horses taken from the farm into the charity's care have fully recovered.
"We are delighted that we can start to look for loving new loan homes for them, where they can look forward to a happy life far removed from the one they experienced in the hands of the Gray family."
He revealed that the cost of care and rehabilitation for the animals had cost about £112,200. The RSPCA has puts its costs for the care of 70 of the horses at £850,000.
Redwings Horse Sanctuary has been caring for 29 of the Gray equines in Norfolk.
Earlier, it thanked not only the RSPCA for its hard work and dedication to the case, but its supporters for their kind words and generosity since that day in January 2008 when it took 30 of its staff and eight of its horseboxes to Spindles Farm.
The charity had described conditions on Spindles Farm when they arrived in January last year as squalid.
Many the animals, it said, were severely emaciated and dehydrated and a good number had lice, bacterial infections and overgrown feet.
"The majority were also pitifully nervous of humans and needed extremely patient and careful handling, including Esther, a two-month old donkey foal," it said on its website.
"Since that date, six more pony and donkey foals have been born (including donkey Timothy) and two further ponies have been brought to Redwings for handling training from one of the other charities involved.
Esther became a celebrity in her own right, with a major fundraising drive - Operation Esther - named after her.
"We know that many of you have, from afar, formed a real attachment to characters such as Esther and Timothy.
"Esther's confidence has grown and grown and today she is a sparky young lady who loves to be around her carers.
"Timothy was born here just a few days after his mum arrived; he is a kind and cheeky soul who demands a bit of fuss from his carers and staff - in fact anyone who passes his paddock!
Chief Executive Lyn Cutress said the Spindles Farm rescue was one of the most distressing and upsetting operations the charity's staff have ever been involved in, "even though sadly we do see equines in distress on an all-too regular basis".
Nicolas De Brauwere, Redwings' Head of Welfare, who gave veterinary evidence during the trial and was present at the site managing the charity's involvement, felt the evidence of cruelty and the extent of equine suffering was so overwhelming that a guilty verdict had been the only possible outcome.
He has no doubt that what he and his colleagues saw that day will remain with them for the rest of their lives.