In seven days the girls treated 70 donkeys and horses for the UK-founded charity, and were struck by the remarkable stoicism of their Luxor patients.
"Most of the animals we saw were pretty thin and all were extremely hard-worked," said Sally. "So compared to the pampered horses we see over here, they were remarkably tolerant of dental treatment and even seemed to enjoy it.
"We had the impression that some of the animals worked almost 24/7, pulling caleches or carriages for tourists in the heat of the day and hauling building materials, sugar cane or crates of pop."
These horses and donkeys are the sole means by which their owners can earn a living and some appreciated the point of bringing the animals off the crowded, dusty roads into ACE for a refreshing shower.
"Although the locals might not love their animals as the British do, some did have respect," said Sally. "But we also saw how ignorance leads to mistreatment in the form of overwork, which was why so many of the animals had open wounds and mouth problems caused by falls.
"It was distressing to see one man spit on his donkey when it sneezed on him and kick it to move it on."
ACE was founded 10 years ago by British charity executive Julie Wartenberg and her veterinary nurse niece Kim. The idea combined equine therapy with a chance for owners to build a closer bond with their animals.
But the need to treat open sores plus more serious conditions set ACE fund-raising for its own clinic.
It now employs 16 staff, including three local vets and at least one other, visiting from an English-speaking country. The next goal is to build an isolation unit for conditions like equine flu. Sally and Sam, who are based in Pateley Bridge, were full of praise for the ACE staff and the facilities. But there were many challenges.
There is no tetanus protection programme in Egypt plus heat and insanitary conditions slow down the healing process.
"Donkeys often have tight little mouths and are always more prone to dental overcrowding," added Sally.
"This, combined with oral damage from stumbles meant that we saw a lot of incisor misalignment and several cases where massive ramps had grown up into the soft palate.
"These were very difficult to reduce enough to give sufficient comfort. But at least we made a start.
"In all my years at vet school and in practice I have never seen a case of tetanus here, but in that one week, two horses were being treated by ACE. They had all the classic symptoms we vaccinate against – erect ears, extended stance with raised tail, locked jaw and joints and sensitivity to light.
"By the end of our stay both horses seemed to be recovering but it was going to be a long process."
Thomas Cook allowed Sally and Sam free excess baggage so that they could take the necessary equipment out with them.
Now keen to continue their work in Egypt, they are fundraising for ACE and are saving for a further trip next spring.