The ISPCA head highlights Clare, Limerick and Kildare as the counties with the highest number of equine fatalities as a result of starvation and neglect.
Another major problem is horses being dumped on land without the knowledge or consent of the landowner.
"Unfortunately, we get kind members of the public who find horses on the road at dusk and turn them into a field for their safety," adds Barbara. "But whoever owns the field is then left with the problem that they did not create.
"It's very unfair and we need to make sure that whoever owns the horses is made responsible."
Financial pressures have taken their toll on the equine population, with many of the abandoned horses not castrated, wormed or treated for urgent conditions.
The result is that there has been uncontrolled breeding among the abandoned animals and there are large numbers of young fillies in foal much too early in life.
"Those fillies are too young to be in foal and my fear is that many of the mothers will be lost in foaling," says the ISPCA chief.
"The animals are starving, full of worms and in foal."
It appears there is no discrimination between the horses that are left to starve, with everything from yearling thoroughbreds to coloured cobs, mares and foals being abandoned.
"It's got to the stage where we cannot cope with the number of horses out there," declares Barbara. "Our policy this year, dictated by our financial position, is that we can only take in animals that we have to as evidence in court cases.
"The day of bringing horses back to the centre to nurse them back to health is over."
At present, there are 55 horses in the ISPCA centres in Mallow and Longford, all of which are ready for re-homing.
However, most of the animals are unbroken -- a factor that works against them.
"Most volunteers would prefer an older, broken animal that is bombproof. However, our animals are rarely bombproof."
The ISPCA chairman is currently working on a programme to enlist experienced volunteers to break younger animals and make them more appealing to foster homes.
The Irish Horse Welfare Trust (IHWT) has also experienced a major increase in the number of calls it receives about neglected and abandoned horses.
"Calls are up at least 60pc or more on previous years," said the IHWT's Sharon Newsome.
"But as usual, we are full with horses."
The Wicklow-based charitable organisation was to the fore in helping 41 horses seized from the farm of Kilkenny farmer Simon O'Dwyer, who has been banned from keeping animals for life.
In what was described as an appalling case by the judge and one of the worst cases of cruelty to horses that Barbara had seen in her 42 years working in the area, O'Dwyer was sentenced to 23 months in jail for multiple counts of cruelty to animals on his farm near Mullinavat, Co Kilkenny.
The farmer pleaded guilty to four counts of cruelty to animals and three counts of failing to dispose of equine and bovine carcasses on lands farmed by him last year.
"We have taken in 70 horses from that farm over the last three years," says Sharon. Happily, all but nine of the 41 horses taken in have been re-homed since Christmas.
However, the charity has neither the funding nor the facilities to take in all the horses it is made aware of.
"I had a typical call this morning: nine horses in a three acre field with no food and depending on rainwater in puddles for water," says Sharon.
"The first thing we do is find out who the landowner is by contacting the local gardai and Department of Agriculture veterinary office.
"There has to be a large number of horses dying out there because we see so many that are so poorly maintained.
"And there is still another six or eight weeks before the grass will start to grow."
However, efforts to encourage owners of malnourished horses to surrender them voluntarily have not worked.
"They tried an amnesty in Limerick where people could surrender their horses to the pound, but it didn't work. Only five horses were given in," adds Sharon.
Meanwhile, the situation in Dublin and its surrounding areas is similar.
Inspectors in the Dublin SPCA had to deal with an incredible act of deliberate cruelty to an animal two months ago.
According to the DSPCA, a group of youths, aged between 13 and 16, attempted to set an injured horse on fire in a field in Finglas, on the N2 southbound near the M50 roundabout.
The animal had been moved by six men earlier in the day covered in straw and left to die. The youths were seen attempting to set the straw on fire by a passer-by, who alerted a nearby animal welfare shelter.
Gardai and DSPCA inspectors attended the scene and the DSPCA vet had to put down the animal. Gardai are still investigating the situation.
DSPCA inspector Liam Kinsella recounted what he saw at the scene: "The poor creature was in very poor condition, it couldn't stand and was totally emaciated. It was a grey gelding of about two years of age.
"This is a scene that is being repeated all over the city and country. Abandoning these animals is horrific, but young people attempting to inflict additional pain on this sorry animal, by setting it on fire, doesn't bear thinking about -- how did it get to this?"
There were five more horses in the same field with no evidence of feed or shelter. Seven more horses, all in a similar condition, were in the adjoining field.
In another case, DSPCA inspectors attended a scene off the Fonthill Road where two totally emaciated horses were found dead in a field.
A staggering 86 other horses were also found in the field, all in various states of distress.
DSPCA inspectors managed to remove two of the worst emaciated horses, infested with worms and suffering from horrific rain scald.
The charitable organisation provided feed to the other horses in the field and is continuing to monitor the situation.
The society has also rescued horses from Damastown, in Dublin 15, and Brittas.
DSPCA chief executive Jimmy Cahill described the cases as "the horrific nightmare, that we were so afraid would happen, has come to fruition".
"We have been trying to raise awareness about this equine crisis for the past 18 months. I am so sorry that it has come to this," he said.
"This is a sorry reflection on our society, more must be done to protect these beautiful creatures. Our resources have been stretched beyond the limit.
"But the DSPCA has been helping all animals for 170 years, and we will continue to do everything we can and be the voice for these beautiful creatures," he vowed.