Although only a limited number of show trainers and their super-rich clients are using in this breeding technique for a despicable mass production, it has disrupted the Arabian horse market for many years already through the disposal of thousands of undesired foals bred out of non-Arabian recipient mares like warmbloods and trotters.
In theory the DNA of embryo transfer foals out of non-Arabian recipient mares remains unaltered but the practice of embryo transfer in non-Arabian recipient mares has in-arguably led to undesired results such as many ET Arabian horses of abnormal sizes or ET foals that have copied the character and movements of their warmblood or trotter recipient-mares.
Several European studbooks have already taken highly necessary measures against this extreme form of animal abuse and disruptive breeding practise: in Poland embryo-transfers are only allowed when the recipient-mare is a pure bred Arabian herself, France has simply limited the registration of embryo-transfers to 1 foal per mare and Spain to maximum 2 foals per mare.
Belgium, home to both several high-profile show trainers and breeding clinics, has meanwhile become one of the most important sources of mass breeding of Arab horses through embryo transfer. A trainer of show horses is expecting this year alone no less than 300 foals (!) for their "privileged" clients. Claiming that this is fine horse breeding is of course utter bollocks, it is collaboration to an extreme form of animal abuse, plain and simple.
The original idea behind embryo transfer was to get a foal from a top mare that either is still in competition or is unable to reproduce herself, not this kind of mass production where hundreds of foals end-up with shady horse traders. There the lucky ones will be sold for peanuts to buyers who think they made a deal of a lifetime but in reality can't even afford to keep horses and the unlucky ones will end-up in the slaughterhouse.
The decision to bring another foal into the world should be done with great thought and care. The offspring should valued to find a good and life-long home.