Barker contacted the SPCA and claimed a veterinarian and farrier had assessed Toppa, but the inspectors later established that the vet was only asked to inspect Toppa's eyes, and not her hooves.
The SPCA visited a week later to find that the pony was now reluctant to move and a vet was urgently dispatched to the property.
The vet found that Toppa was lame in both front feet, with severe laminitis, which can cause the animal intolerable suffering.
The vet also said that any lay person could and would see Toppa's gait and appearance was abnormal.
As the condition was so severe and was not able to be treated, on the vet's recommendation, Toppa was euthanised in order to end her suffering.
SPCA chief executive Andrea Midgen said that the prosecution was evidence that "good intentions are not enough".
She said: "In this case, Toppa was left to suffer for a long time, her condition worsening while she was at Horse Havan.
"The fact that her condition would have been obvious to any lay person is particularly distressing, as her pain was ignored by those at Horse Havan who should have known better."
Last Friday Barker was sentenced to three months community detention, 100 hours of community work, disqualified from owning any animals for 6 years and ordered to pay reparations of $860.45 and $282 in solicitors costs.