HGG Community Forums

For context here is the original post about the agouti overhaul
https://www.huntandjump.com/forum/discussion/54623/changes-are-coming-to-agouti-here-is-what-you-need-to-know#Item_34

All horses who had the t allele in the game now have A*. A* is a placeholder to help people with the transition. As the former t allele holding horses age out of the game, A* will vanish over time. When you breed a horse with A* any foals it has will only inherit normal A. You can not edit A* onto any horses.

A* is exactly the same as the old t allele and follows those rules when creating the brown phenotype and color name.


New brown rules
All horses, including foals of A* horses, now follow the new brown rules. To be marked as brown a horse must have 4 or more darkening conditions. This works like liver/chocolate for ee horses. They require 3 darkening conditions, brown requires 4.

What is a darkening condition?
With our liver horses each copy of sooty and each copy of DP count as one darkening condition. This will be true with brown horses as well. In addition to sooty and DP being EE or Aa will also count as a darkening condition for brown horses.

EE = +1
Aa = +1
Sty/- = +1
Dp/- = +1
Sty/Sty = +2
Dp/DP =+ 2

Agouti promoter reduces brown counters. Every copy of Agouti promoter acts as a-1 darkening condition.


Exactly what genetic combos will be bay versus brown?
I have made a spreadsheet
https://docs.google.com/spreadsheets/d/1EHr5iP5D8NNHME1LWc-6tgpwupd_BdZpuMKeqNBnZuI/edit?usp=sharing

Will DP now be required for brown?
No, EE Aa StySty horses will brown even without the DP gene.

Exactly what genetic combos will be bay versus brown?
I have made a spreadsheet
https://docs.google.com/spreadsheets/d/1EHr5iP5D8NNHME1LWc-6tgpwupd_BdZpuMKeqNBnZuI/edit?usp=sharing


Herd Helpers
The former herd helpers that had the t allele have all been straight edited to have the A allele. That means many of the formally brown herd helpers will no longer make brown all the time. They will make sooty bays instead. Many of these horses can still end up as browns, it just is not guaranteed. There will be new brown-only herd helpers coming in the future.


Future agouti generation
Right now the generator has some relatively harsh lines between wild bay, bay, and brown. It also is struggling with buckskins. There should be a smooth gradient of expression from very little black point remaining all the way to nearly fully black expressions of agouti. My plan is to rebuild agouti this fall. The aim is around November but we will see how things line up. Looking forward to it!


Please let me know if you have any questions.