As was the case for all the predator and pest species currently living with you on your planet, which were introduced by the interlopers to be a scourge as a punishment for humanity, the horse was an extraterrestrial species, but from a loving world that was functioning well at the time of its creation, and it served in much the same way as enjoyed by human culture, being a perceptive and cooperative companion. The horse was used in this interstellar world as a source of energy and pleasure, both, and actually was enjoyed greatly by the beings of that world who had an ability to communicate intuitively, and thus could foster a quite high level and close relationship that was mutually satisfying and rewarding for both species. Even while providing a service to the higher-level sentient inhabitants of that world, the horses of that period found it quite rewarding, so it was a mutually beneficial relationship in all respects because the horses, in turn, were treated well by the loving beings who were, in turn, benefitted from their cooperation.
The introduction of the horse in the human world was a repurposing of a good idea with a proven track record and is but one of many, many things that were done to prepare the world for human habitation, in building a loving nest with creatures of all kinds to support human life, and a long-lived civilization so you could thrive and prosper living off the land and its environmental bounty. While humans were reconfigured prior to being launched in the second seeding, the horse did not need any major changes because it already had the inner capability and flexibility to serve humanity, and its karmic history, in serving other sentient beings, was advantageous and not a liability. There are many horses with karmic woundings at the hands of humans who became corrupted, so there are many historical abuses of horses at the hands of human beings, and that is part of the karmic legacy for humanity needing healing because you have been perpetrators at times when out of alignment, by abusing animals around you.
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