In fact the poor animal, who was with four other severely neglected Arabian ponies, was just hours away from death.
Too weak to stand, she was emaciated and riddled with lice, and her skin was sore and infected as a result of rubbing from the irritation of lice and worms.
And horrified staff from the Bransby Horses rescue centre who came to take the animals to safety doubted that Emerald, the weakest of the horses, would find the strength to survive.
As they tried to get her to the horsebox, Emerald managed to get up and made it inside with assistance, but then collapsed again and was too weak to get back on her feet.
While the rescue effort was taking place, the owners were aggressively trying to stop it, blocking the entrance and even driving a car into the horsebox, until they were restrained by police.
Ryan Rouse, the charity's head of external welfare, remembered the moment he came across Emerald: "The first thing that hit me was the smell. My worst fears were confirmed as I laid eyes on five horses which were in a terrible state and living in absolute squalor.
"Their bedding had completely deteriorated and they were standing in a thick layer of faeces and urine. We had no idea how long they had been living in those conditions."
While the other four horses responded well to medication and quickly showed signs of improvement, Emerald was no longer able to stand and it quickly became clear she was seriously ill.
But the team at Bransby Horses worked round the clock caring for the horse, lifting her to her feet every two hours, day and night, for three weeks, using a special harness.
Lying down for too long was dangerous as it could lead to pressure sores, stomach ulcers and problems associated with infrequent passing of droppings and urine.
The physically and emotionally draining care effort was rewarded when Emerald was finally able to get up on her own after four weeks, but even then the team knew she wasn't out of danger.
A camera was also set up in the stable to keep a constant watch on her, and in the night if she was down again for too long, five people would get out of bed to lift her.
Emerald's blood counts continued to improve, she gained weight and her medication was decreased as against all the odds she battled back to health.
Team member Lou Evans said that caring for Emerald and the other four Arab mares was "the most physically and mentally challenging case the team and I have dealt with.
"Each mare required such specific treatment for a range of injuries and ailments.
"Seeing them well and loved today is a huge achievement for us all. It could have been such a different ending if they hadn't been found when they were."
Emerald, along with the other horses, remains under the care of Bransby Horses and once fully recuperated, will be rehomed.
The woman responsible for the horses' appalling treatment was banned from keeping horses for five years.
Claire Hogarth from Bransby Horses, which looks after over 400 other animals at their rescue centre in Lincolnshire, said: “We've all been through so much with her and we've all become very attached to her. She was breathing her last breaths when we found her, you might have thought that she was already dead.
"To see how she's bounced back and recovered is incredible, and the people who cared for her and got up through the night were amazing.
"We are now hoping that we'll soon be able to find a loving home for her."