If your into Bestiality
Z-ton's work might interest you the book
Does This Strange Body Please You? Its Monster Girl tag but the girls do have Horse, Sheep and Deer bodys. Its as close as you will get on this site anyway to Bestiality. If you find that works for, you also try some of
Mizone's work.
Could also give this a shot
Futanari Teacher Morita Ritsuko. Its Futa but her dicks shaped like a horses.
Hope this helps.
Keep on Fapping