Short Mane and Unicorn Mane for your large Dogs.
For more options for your companions. Create your fantasy animal in the Sims 4 with this Mane
Category / Neck Accessoire
Long Mane: https://www.curseforge.com/sims4/pets/long-mane-unicorn-mane/
Horse Hoof: https://www.curseforge.com/sims4/pets/hoof
Horse Head: https://www.curseforge.com/sims4/pets/horse-head
Horse Tail: https://www.curseforge.com/sims4/pets/horse-tail