Managing and maintaining COI - a guide

[Emiisheartless2]

A guide to managing the COI in your herd

While there are no negative effects of high COI at the moment, it has been suggested that it will be introduced at some point. Therefore, we have been adviced to find ways to lower and maintain the COI in our herds, Most guides to managing COI recommend breeding your horses to an unrelated horse now and then in order to limit inbreeding, but this method only works to a certain extent. Without actually trying to manage the level of inbreeding in your herd, the COI will just keep on increasing, no matter how many times you breed to an outside horse. Thankfully, admin has capped the COI at 200%, but getting it down to reasonable levels is almost impossible unless you're willing to sacrifice a lot of your herd's progress. So, how do we avoid this?

The solution is in the size of the herd. Think about real-life horses. We are able to maintain low levels of inbreeding, or avoid it altogether, all thanks to the sheer number of horses. So, how do we implement this into the game? Well, we just need the herd to be big enough. The only question is: how big does the herd need to be? Do we need a hundred horses? Two hundred? Maybe even three hundred?

Nope.

32.

That's the number of horses needed per generation in order to make sure the COI is never increased. However, just having the right amount of horses is not quite enough. Since we're working with the smallest number of horses we could possibly have without increasing the COI, we need to breed them in really specific patterns to make sure we don't accidentally pair a couple of cousins or siblings with each other. Well, after a few weeks of thinking and testing, I've figured it out.

So, without further ado, here it is.

A quide to managing and maintaining COI.

Step 1
Get 32 horses, evenly divided between the genders. They can be AC stock, or a bunch of full siblings with maxed out COI. It doesn't really matter, just know that this method mainly maintains COI rather than lowering it, so if your horses have really high COI you probably wont notice a difference for the first 50 generations or so.

Step 2
Assign each stallion a number between 01 and 16 and add an "A" before the number. You'll get A01, A02, A03 etc, all the way up to A16. The mares don't need numbers, but you can give them some anyway if you're afraid they're going to feel left out.

Step 3
Pair the horses up. This method is based on having fixed pairings, which means every horse will have a single mate to breed with. This makes it a lot easier to keep track of who's related to whom.

Step 4
Breed them! Breed each stallion to his mare, and keep breeding them until you have one colt and one filly from each pair. The foals inherit the number from the sire, but with a new letter at the beginning. For example, the stallion A01 sires foals named B01, A02 sires B02 etc.

Step 5
New mates! We now have 32 new horses that are going to be mated. In order to make sure no inbreeding occurs later on, follow this guide where the left horse is the stallion and the right one is the mare.
B01 - B03
B02 - B04
B03 - B01
B04 - B02
B05 - B07
B06 - B08
B07 - B05
B08 - B06
B09 - B11
B10 - B12
B11 - B09
B12 - B10
B13 - B15
B14 - B16
B15 - B13
B16 - B14

Step 6
Breed. Once again, we want a colt and a filly from each pair. Foals still inherit their sire's number, but this time it is preceded by the letter C. So B01 sires C01, B02 sires C02 and so on.

Step 7
New mates again. This time, the pattern looks a bit different, but stallions are still on the left and mares on the right.
C01 - C05
C02 - C06
C03 - C07
C04 - C08
C05 - C01
C06 - C02
C07 - C03
C08 - C04
C09 - C13
C10 - C14
C11 - C15
C12 - C16
C13 - C09
C14 - C10
C15 - C11
C16 - C12

Step 8
More breeding. As usual, we want a colt and a filly from each pairing. They inherit their sire's number, this time preceded by the letter D.

Step 9
Pair 'em up!
D01 - D09
D02 - D10
D03 - D11
D04 - D12
D05 - D13
D06 - D14
D07 - D15
D08 - D16
D09 - D01
D10 - D02
D11 - D03
D12 - D04
D13 - D05
D14 - D06
D15 - D07
D16 - D08

Step 10
To the surprise of absolutely no one, we breed these horses too! A filly and a colt from each pair, inheriting their sire's number which this time is preceded by the letter A. D01 gives A01, D02 gives A02, D03 gives A03 (hihi). It may seem strange to jump from D back to A, but all will be explained.

Step 11
These horses are paired following this guide:
A01 - A02
A02 - A01
A03 - A04
A04 - A03
A05 - A06
A06 - A05
A07 - A08
A08 - A07
A09 - A10
A10 - A09
A11 - A12
A12 - A11
A13 - A14
A14 - A13
A15 - A16
A16 - A15

Step 12
Once again, we breed. The sire's number is now preceded by the letter B.

Step 13
Breed the new horses using the guide in Step 5 and just keep following the instructions from there.

- - -

As you see, once you've done the fifth generation of horses, it all starts over from the beginning. Now, the foals you produce in this generation won't be inbred themselves, but they do inherit their ancestors' inbreeding. So if all the ancestors are maxed out at 200%, the foals in this generation will have a COI of about 194%. This will decrease by about 3 percentage points per generation, though the decrease will get lower as the COI also gets lower, so it will take you around 50 generations to get the COI down below 100%. If the COI of your herd is already 0%, that's great! Using this method ensures that it never increases (assuming you follow the guide meticulously).

Keep in mind that despite your horses not having an increasing COI, they are still very inbred. If you were to look at the sixth generation, you'd see that every single horse occurs twice in that generation. It's lucky the game only looks at five generations...

Tips and tricks
Utilize the All Horses view on your farm, and sort the horses alphabetically. This also sorts them numerically, which makes it really easy to make sure you have your two A01's, your A02's, A03's and all the other ones.

If you want to speed the process up a bit and get the satisfaction of seeing some progress now and then, you can replace one horse with a 0% COI one every fifth generation. It can be the same one every time, which saves you the hassle of finding a new one every time.
In the long run, it doesn't make that big of a difference, but it is a bit satisfying to see the COI drop drastically from one generation to the next, and it does give you a chance to keep track of your progress a bit.

While progress will be a lot slower than if you were to completely ignore the COI, there are still ways to ensure you get a nice amount of progress per generation. Instead of "retiring" a pair once they have produced a colt and a filly, you can keep breeding them and replace the foals as you get better ones. Just make sure you always have a filly and a colt if one of the horses passes unexpectedly. If you're going to do this, I recommend keeping the foals on a freezer account so they don't get too old, and to ensure you can breed the entire generation at the same time. Doing this ensures that you don't mix the generations up and that no horses have time to retire before their partners are even born.

Let me know if you have any questions and good luck with your horses!

[Silverine]

A very useful write-up! Thank you for this!

[Argent II]

As you see, once you've done the fifth generation of horses, it all starts over from the beginning. Now, the foals you produce in this generation won't be inbred themselves, but they do inherit their ancestors' inbreeding. So if all the ancestors are maxed out at 200%, the foals in this generation will have a COI of about 194%. This will decrease by about 3 percentage points per generation, though the decrease will get lower as the COI also gets lower, so it will take you around 50 generations to get the COI down below 100%. If the COI of your herd is already 0%, that's great! Using this method ensures that it never increases (assuming you follow the guide meticulously).

Curious about this statement. Have you successfully brought COI down from 200/100%+ to under 100% using this method?

[Emiisheartless2]

Curious about this statement. Have you successfully brought COI down from 200/100%+ to under 100% using this method?

Actually, I am almost there with my Icelandics! I wouldn't have written this guide if I wasn't sure the method worked
I believe my horses started out at around 130% so not quite maxed out at 200%, but they are now just a few points over 100%. It's only taken about 13 generations to get them there, so while the method is mainly for maintaining the COI, it is also quite effective when it comes to decreasing it

[Argent]

Actually, I am almost there with my Icelandics! I wouldn't have written this guide if I wasn't sure the method worked
I believe my horses started out at around 130% so not quite maxed out at 200%, but they are now just a few points over 100%. It's only taken about 13 generations to get them there, so while the method is mainly for maintaining the COI, it is also quite effective when it comes to decreasing it

How have you verified that COI is coming down behind the 100%+? Outcrosses to 0 COI horses to test?

[Emiisheartless2]

How have you verified that COI is coming down behind the 100%+? Outcrosses to 0 COI horses to test?

Exactly
The first time I tested them, the foal ended up being in the high seventies. Now, 10 generations later, it came out at 52%. Since the foal’s COI is approximately half the inbred parents COI (minus a sixteenth of the fifth generations average), I assume the rest of the herd is at around 105-110%. With an average decline in COI of about 2.5 percentage points at this stage, I should reach the 100%-mark in five generations or less

[Argent]

Curious about this statement. Have you successfully brought COI down from 200/100%+ to under 100% using this method?

Actually, I am almost there with my Icelandics! I wouldn't have written this guide if I wasn't sure the method worked
I believe my horses started out at around 130% so not quite maxed out at 200%, but they are now just a few points over 100%. It's only taken about 13 generations to get them there, so while the method is mainly for maintaining the COI, it is also quite effective when it comes to decreasing it

Do you still have this project going? I'm curious to see how it's progressing

[Emiisheartless2]

Actually, I am almost there with my Icelandics! I wouldn't have written this guide if I wasn't sure the method worked
I believe my horses started out at around 130% so not quite maxed out at 200%, but they are now just a few points over 100%. It's only taken about 13 generations to get them there, so while the method is mainly for maintaining the COI, it is also quite effective when it comes to decreasing it

Do you still have this project going? I'm curious to see how it's progressing

I’ve taken a break from this particular project, as I’m waiting for genetic testing to be made available, but I did manage to get the COI of my herd down to around 90%. Here you have an example:

D01


As you can see, he has three horses with 0% COI in the fifth generation in his pedigree, which does help bring his COI down slightly, but not all that much. Had I not introduced any 0% COI horses at all, the COI would still have fallen under 100% by this point. I have a whole spreadsheet of calculations on COI, so if you have any questions, don’t hesitate to ask!

I have also started a new project where I have managed to avoid inbreeding completely for over 10 generations, while still allowing for improvement in performance, and while progress is slower than if I could breed however I wanted, I have still seen a decent amount of growth.

To end things off, I’ve also started looking at how this method could be used when creating a new breed and concluded it is possible to decrease the amount of horses one needs by a whole lot by reusing some individuals.

Thank you for checking in!

[Argent]

I’ve taken a break from this particular project, as I’m waiting for genetic testing to be made available, but I did manage to get the COI of my herd down to around 90%. Here you have an example:

As you can see, he has three horses with 0% COI in the fifth generation in his pedigree, which does help bring his COI down slightly, but not all that much. Had I not introduced any 0% COI horses at all, the COI would still have fallen under 100% by this point. I have a whole spreadsheet of calculations on COI, so if you have any questions, don’t hesitate to ask!

My upcoming project is starting at about 110% COI, and my goal is about 40%, so we’ll see how this goes. By the sound of it, it’ll take dozens of generations

I have also started a new project where I have managed to avoid inbreeding completely for over 10 generations, while still allowing for improvement in performance, and while progress is slower than if I could breed however I wanted, I have still seen a decent amount of growth.

To end things off, I’ve also started looking at how this method could be used when creating a new breed and concluded it is possible to decrease the amount of horses one needs by a whole lot by reusing some individuals.

Thank you for checking in!

For sure. Repeating horses will allow me to create Thoroughbreds with just 16 AC horses instead of 45. And I just wrapped up a low COI project that started out as a zero COI project, and I saw a solid 4% increase in dressage scores in just 4 or 5 generations with no inbreeding. Definitely possible even though it does taken time. After allowing in inbreeding, I got the project herd within 2% of my old herd’s scores after another 4 or 5 generations of breeding, with COI staying around 30%.

[Argent]

Can this be pinned