Id love to see a way to bulk sell a herd of horses. like for say a mare and stallion or like 3 stallions 5 mares... 

This is what the forums are for, you can state exactly what you're selling and people reply with an offer...

If I am looking for a whole herd I always go to the animal sales page of the forums like Tana said. You can then advertise your link to your forum thread in advertising chat to help it get more views.