The league launched an appeal on 20 April that asked recipients to donate money by 6 June to provide relief and training in horse care, saddlery and farriery in Mexico.
The appeal raised £153,000 and had a response rate of 12.8 per cent.
There are about 2,000 horses being worked to death in Mexico's rubbish dumps. The league has run a project to care for horses in the country for a number of years, but only recently brought it to the attention of its donors.
After a full review of the project early this year, the charity decided to invest more in it. Linda Hams, the league's director of fundraising and communications, said the charity had just heard that its local TV channel, Anglia TV, wanted to run a programme on Mexico's rubbish dumps.
She said that although the news did not have any impact on the league's decision to continue its work in Mexico, it did boost confidence. "Media coverage is not always what counts," she said. "Our main concern has to be with what benefits animal welfare."
How it worked
There were two versions of the appeal - one aimed at 47,000 warm donors and another at 25,000 cold donors.
The language and text used in the warm appeal was similar to that of the cold mailing, the only difference being a hand-written post-script message by the league's international training manager Ian Kelly.
In the warm appeal, Kelly thanked donors for their support, while in the cold one he pressed home the fact that the league relies totally on donations for its income.
The letter told the story of a horse that was used by its owner to carry loads of rubbish at Mexico City's rubbish dumps. The appeal used a hard-hitting message, describing the horse's horrific treatment and eventual sale at a meat market after it broke its knee.
The pack also included a leaflet with images of ill-treated horses. Instead of blaming the people who work on the dumps, it explained that they are too poor to take care of their horses, spending any money they earn on their families.
The leaflet also suggested a range of donations from £20 to £250, which would, for example, pay for a kit to train farriers and saddlers to look after the horses. The basic ask, however, was £20.
To date, the appeal has raised £160,000.
The warm appeal raised £153,000 against a target of £170,000 and had a response rate of 12.8 per cent. The cold appeal raised £7,000 against a target of £20,000 and had a response rate of 1.2 per cent. The average donation for the warm appeal was £24.57.
Linda Hams said she was pleased with the cold mailing's response rate.
"Our target was a 4 per cent return, which is 10 times what people usually expect," she said.
She added that the league's trustees set high targets because they are keen to increase the charity's fundraising.
"We have constantly increased our response rates in recent years and have done better than others," she said. "I think we are lucky that our field is quite narrow. There are very specific lists that we can buy to target the right people."
Drew Corps, creative director, Navig8
Attitudes towards animal welfare in many countries do not necessarily measure up to our own. The ILPH has been protecting horses' welfare since 1927, and part of its work has been with the horses that work the Mexican rubbish dumps.
Some 40 per cent of the Mexican people live in poverty, earning less than a dollar a day. These workers scratch out a living in the rubbish dumps.
A knee-jerk reaction might be, "sod the horses, what about the people?" But that view is hard to justify and is not the league's mission. It is appalling that people should have to earn their living in this way, but they are the 'lucky' ones - many thousands of people in Africa die because they do not have access to treatment or the basic necessities of life.
The scale of global poverty is so daunting that one wonders if there is anything you can do that will make a difference.
The campaign targets seemed high, and the warm appeal did achieve a high return. Not being a particularly 'horsey' person myself, I couldn't really see what a 'clench groover' or a pair of 'clenched tongues' would actually do to help.
But the material was well put together. It was a harrowing story and did make me feel that something should be done.
In all, this campaign was a success. I could see that the horses were these people's livelihood and that blaming them for mistreating the animals would do no good. Training the workers to help keep their assets fit and healthy would go some way to making the horses', and their owners', lives a little better.