What did Gulliver tell the great houyhnhnmabout the treatment given to hourses in Gullier'sland? What was his reaction to this?

Gulliver told the great houyhnhnm that the horses in Gulliver's country were friendly animals that had great strength and swiftness. The horses belonging to people of higher class were useful for travelling, racing or drawing chariots, while those employed by farmers were treated worse as they had to do more labour and were ill fed. The horses were trained, at a young age, to pull carriages and follow the orders of the yahoos.They were beaten for their mischief and in order to tame the ones employed for common riding or draught, the male horses  were castrated when they were two years old.

The great houyhnhnm resented the use of one of their kind for carrying the yahoos. He considered the horses' treatment as ghastly and found the castration of male horses as savage and incomprehensible as he believed that reason prevailed over strength.