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Making New Breeds and Specialized Breeding
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EclipticEnd
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Making New Breeds and Specialized Breeding
This'll be long so please don't quote this. Thanks! 
Before we go into detail about specialized breeding, let's look at the basics of breed creation.
Evaluations: Evaluations tell us how well a horse fits a breed's standards. This is mostly used for making new breeds, but can also be used to keep your herd within the standards of the breed that you're working with. Because it shows a breed's standards, you want to use the evaluation book of your target breed. You can get evaluation books in the Book Store in the Market, and you use them under the Eval tab in a horse's page.
Evaluations show the following physical characteristics of the horse:
Height: How tall a horse is. The unit hh means hands heigh. I believe one hand is thereabouts 4 inches. From what I understand, a real horse above 14.2hh is considered a horse, and one below that is considered a pony. Drafts are around 16hh+.
Build: How light or heavy a horse is. Lighter horses tend to be more of a racing build while heavier horses tend to have more muscle for log pull. This goes via the following scale: Very Light -> Light -> Medium Light -> Medium -> Medium Heavy -> Heavy -> Very Heavy. The game notes that while this is a reference, it's not necessarily required to match for making new breeds. Medium tends to be the middle ground. Anything left of Medium wants to keep going left, and anything right of Medium wants to keep going right. Therefore, Light + Light often makes Very Light, Heavy + Heavy often makes Very Heavy, and Heavy + Light will theoretically be somewhere in the middle.
Body Size: The bulk of a horse. Very light horses like Arabians might have 0% size, whereas heavier breeds like Belgians may have a much higher percentage.
Type: Horse vs. Pony type. Horse type horses will look... like a horse. Pony type horses will be ponies and drafts. This uses the following scale: 100% Horse -> 0% Horse / 0% Pony -> 100% Pony.
Evaluations measure the match to the breed's standard in stars. The scale goes from 5* -> 4* -> 3* -> 2* -> NA. You cannot get a 1* evaluation.
If nothing matches then you get an N/A match, which means the horse will be a terrible choice for breeding the evaluation breed. If you only have one matching attribute, then it will always be worth two stars and will be a poor match. Two matches will be worth three stars, which will be an okay match. Three matches will be worth four stars or a great match, and all four matching is worth five stars, which would be a perfect match.
Please note that terrible, poor, okay, great, and perfect matches are not officially referred to as such; I'm just adding that in to give you a better idea of how the stars correlate in terms of a match for a breed.
Generally you want your eval to be four or more stars, as this will give you a better chance at a quick success. The less stars you have, the less of a probability you'll have of getting a foal of your target breed. At three stars or less, you may end up having your horse nearly or completely retire before you can get that new breed.
Also, because evaluations are incredibly important to breeding, you have to be aware of how different horses will match together. It's better if both are 5* evaluations, but if they're not then you can try to balance it out.
If you have a horse that's too tall for your eval, you can balance it by matching it with a shorter horse that might be either too short for the eval or simply on the lower side of the requirements.
If you're pairing two Light build horses, it's likely that you'll get a Very Light foal rather than a Light foal. Likewise, if you match two Heavy horses, you'll probably get a Very Heavy foal. Medium horses tend to stay Medium when bred together as that's the center of that scale. Therefore, if you have a Light horse and you need a Medium, try mixing with a Heavy horse if possible. If you need a Very Light horse, then using two Lights or a combination of Light and Very Light will work. Very Light + Very Light will likely always result in Very Light. Very Heavy + Very Heavy will likely always make a Very Heavy. Those are the maximums for either side of the scale.
Size has been a bit more unpredictable for me, but it's thereabouts similar. Lower percentages tend to like to stay low, whereas higher percentages like to stay high. I've had a 58% and a 52% make both an 82% foal and a 35% foal. It's a bit random sometimes. My advice would be that anything under 50% will possibly make a lower percent, anything over 50% will probably make a higher percent, and there will always be odd outliers.
As for Type, keep in mind the scale. Horse type goes down to zero, and on the other side of zero is Pony type. Likewise, Pony type goes down to zero, and Horse type's on the other side. The less of a percentage it is, the closer it is to the other type. This is balanceable; using a higher Horse type will lower the Pony type percentage and vice versa. Using two Horse type or two Pony type will boost that type.
Continuing forward. The evaluation is incredibly important, but it's also important that you're using the correct breeds in order to make your target breed. These can be found via the Breeds Wiki. If you click on a horse, then it will tell you the horse's recipe on the right side of the screen (so long as they're not Adoption Centre breeds). 100% recipe horses are ideal, but you can get away with using "Part [breed]" so long as it's the only breed listed. For instance, you could use a Part Tarpan to make an Exmoor, but you cannot use a Part Tarpan x Turkmene to make an Exmoor.
You can also use this amazing collective list made by Silverine. This has a list of all of the breeds in the game in an order that can be used to complete all of the breed quests in the game. This is also a good reference to see what crosses can be used where and how. I highly advise taking a look at their post.
To make a horse breed you'll need at least two horses. Many breeds require crosses between a variety of breeds. Your breed could be as simple as the Akhal-Teke (Arabian X Turkmene) or as complex as the Welsh Mountain Pony ([Thoroughbred X Hackney] X [Exmoor Pony X Arabian]). It's always good to make note of what horses you're going to need to mix in order to reach your two main recipe horses, which you'll then breed together to make your target breed.
Many recipe horses can be found via the public studs, but some are rare enough that you'll have to make them yourself. Take this into account before trying to make a complex horse. If you have to make your own recipe horses then they'll need time to age before they can be used, and the last thing you want is for your horses to retire while you wait for that, or for you to have to freeze things entirely while that happens. Always make or find your recipe horses before you start that breed.
=====================================================================================
So, onto the main part. Specialized Breeding in this case would be taking a breed and altering it to fit into a certain evaluation. There's multiple instances where the normal build of a breed really doesn't fit into a recipe that it's used in. Since you want a 4*-5* eval for both horses, this can be an issue.
I'll use Arabians as an example, but feel free to substitute any breed that you want.
The base evaluation for an Arabian horse is as follows:
Height: 14.0hh to 15.3hh
Build: Very Light to Light
Body Size: 0% to 20%
Type: 100% to 78% Horse Type
As you can see, Arabians are a very lightly built horse breed. They're on the extreme side of light. As an Adoption Centre breed, they're also one of the base horses and are used to create a multitude of new breeds.
This becomes an issue when we have a heavy built pony breed requiring Arabians that we have to make. Ergo, specialized breeding must take place in order to make Arabians fit the needs of the new breed. I'll use Spiti as an example, as I've successfully bred one of these myself via this method.
Spiti horses are as follows:
Height: 11.0hh to 13.1hh
Build: Medium Light to Medium Heavy
Body Size: 35% to 60%
Type: 65% Horse Type to 70% Pony Type
As you can see, the Spiti evaluation is very different to the Arabian one. Spiti are shorter, heavier, bulkier, and much more Pony type.
Spiti are made by crossing an Arabian and a Tibetan Pony. We already know the Arabian evaluation, so here's the Tibetan one for reference:
Height: 10.3hh to 13.0hh
Build: Medium Light to Medium
Body Size: 40% to 60%
Type: 70% Horse Type to 60% Pony Type
Tibetans can certainly offer a fair deal of balancing for this recipe. They tend to be shorter, which can counteract the fact that the current non-AC Arabians are rather tall, some being upwards of 18hh. They're heavier built, so it could be possible to reach the Medium Light side of the build requirement... if the odds are in your favor. The Size is 40-60, but as Arabians are 0-20 that might be a hard balance unless you manage to get a 20% Arabian and a 60% Tibetan. Type isn't bad, but you must remember that Arabians can go up to 100% Horse type, which is a hard balance to reach re maximum of 65% when your Tibetans might end up being their maximum 70% Horse Type.
So, how do we fix this?
My answer would be cross breeding the problem breed (Arabians in this case). I don't believe that there's naturally an AC Arabian that's outside of a 5* Arabian evaluation. As such, we can't really make a heavier Arabian just from breeding Arabians together. We'll have to take a heavier breed, mix it with an Arabian, and then breed that cross back to pure while keeping our desired characteristics. The horse doesn't have to eval to a 5* Arabian, after all, just a high star Spiti.
This will take time to do, and require a fair amount of room, but I find that it's very much worth it for the end result.
From the Adoption Centre we get these breeds:
Arabian, Belgian, Caspian, Forest Horse, North African Barb, Przewalski Horse, Shetland Pony, Tarpan, and Turkmene.
If we want to keep a higher HGP, then the best horses to use when altering builds would probably be Arabians, Belgians, and North African Barbs. These are breeds that have had a lot of work put into them, and therefore are often higher quality and better established than the other listed breeds. There are exceptional horses in each breed, of course, but to my knowledge these three are generally the most established of the base breeds.
Arabians, as already stated, are on the extreme side of light horse type. You'll use these if you're making a heavy breed lighter and more Horse type.
Belgians are more on the extreme heavy pony type side. You'll use these as well as Shetlands to make your breed heavier and Pony type.
North African Barbs also tend to be light horse type, but not as extremely as Arabians. You can find Medium Light and Medium NABs, whereas you're unlikely to find Medium (Light) Arabians. You'll likely use these for a less extreme light type.
You can also use non-AC breeds if you'd like such as Thoroughbreds and Quarter Horses, just take note of their evaluation stats so that you know how they'll impact your breed.
In this case, we can use Belgians and NABs to get a heavier, bulkier Arabian. I personally chose Belgians as they're Pony type, bulkier, and a heavier build. The only issue is they're much taller than the Spiti evaluation. To fix this we can cross in some Shetland blood; Shetlands are also heavy, bulky, and Pony type, they're just much smaller and might not have HGP to the standard of Belgians. You'll find that Shetlands and Belgians will probably have a 4* evaluation for each other, the odd part out being height of course. If HGP is a worry for you, then I suggest using high HGP Arabians to counter the lower HGP Shetlands that you might find.
The plan will be to breed your Arabians with a Belgian and/or Shetland until you get a decent foal. You'll then breed that foal to an Arabian upon breeding age until you get another decent foal, and you'll repeat that until you have a 100% Arabian. You can certainly use Grade horses instead of Belgians or Shetlands and stop when the breed reads as "Part Arabian", but I'll be typing this as if you're using a purebred Belgian/Shetland and therefore I'll be referencing "Arabian x Belgian [50%]" and such.
Let's go into more detail now.
To start with, you'll have to pick out your founding Arabian(s) for this project. The number you choose will depend on the amount of room you have. Keep in mind that you'll be going through multiple generations of horses to create your target Arabian.
To be more exact, you'll be making a 50% Arabian, an 80% Arabian, and a 95% Arabian before you hit that 100% goal. You'll probably have more than one 50% Arabian, more than one 80% Arabian, and more than one 95% Arabian. You'll also be breeding together 50% Arabians and 80% Arabians to try to get better evaluations. Expect to use at least one barn for the Broodmares, one barn for the Studs, two pastures for the foals, and at least one pasture for aging out horses.
If you're limited in space due to your max horse limit (which can be increased via player skills) then consider starting with only two Arabians. I'd suggest using mares. You'll want to choose Arabians that have high HGP (if that matters to you), are Light rather than Very Light (if you can find them), and are as high as you can find for Size. These won't overall play a large part later, but it makes changes happen much more easily than taking that extremely light, 0% bulk Arabian as your founder.
Next, find your studs. You can use your own, or use public studs. Assuming you're starting with two mares, I'd suggest breeding one to a Belgian and the other to a Shetland. This will give you two height extremes; the Belgians will be tall and the Shetlands will be short. Swap out with what studs you use if you're worried about COI; you'll be breeding foals together a lot.
Then you wait. Eventually those mares will have their foals. When they do, evaluate those foals for Spiti and see what their statistics are. In an ideal world, you'll get some good matches; however, this can often be difficult. Don't immediately rehome any horses that are poor matches.
You're going to want to breed your 50% Arabians together in order to get better results if the foals you're getting aren't ideal.
Be picky at this stage. I suggest putting down their evaluations and HGP in their descriptions so that you can immediately know what horse would pair best with another. I do this with my Tarpans if you want an example. Those are evaluated for Mongolians.
You want to go for the extreme heavy/bulky/pony side here to balance the extremely light/thin/horse Arabians. See if you can't get any Heavy or Very Heavy 50% Arabians; if you can, then aim for type next and get some Heavy, Pony type Arabians. Then you can try for bulk if you'd like. If they're too Heavy/Bulky/Pony for the Spiti eval then that's 100% alright. Matching them with Pure Arabians is going to lower them back down. Just remember not to breed siblings or half-siblings if you're worried about COI. You can easily keep below a 30% COI if you're careful enough and have enough genetic variance.
Also, as a note: breeding an Arabian x Belgian [50%] to an Arabian x Shetland [50%] will leave you with a Half Arabian [50%] if you're not looking to try for a 100% Arabian and are instead trying for a Part Arabian. So long as the percentages match, you shouldn't get a Grade Horse.
Keep breeding your crosses until you get a foal that you like, then let the foal age to breeding age. At this point you want to breed that foal to another purebred Arabian. You can use one of your mares if the foal is a colt and you don't care about COI (else get a new, unrelated mare at this point and move the others to your age-out pasture), or you can use an Arabian stud if it's a mare. The resulting foals will now be 80% Arabians. You can keep going with your 50% crosses to make more 80%s until you're happy with the variety, then move your 50% crosses to your age-out pasture (or rehome them if they didn't end up having foals).
At this point you want to begin narrowing down to a 4* or 5* evaluation. Repeat what you did with the 50% Arabians; breed those 80% foals together until you get something good, then age that foal and breed it to a purebred. The resulting foal will now be 95% Arabian. Freeze it if you don't have a good selection of this generation yet and keep crossing your 80% Arabians until you do.
If Arabian is the only breed listed, then these foals can be used for breeding your Spiti. You only need a Part Arabian for breeding new breeds. If Belgian or Shetland is still listed, then you'll have to breed to a purebred again in order to get a 100% Arabian.
Again, breed your 95% Arabians until you're happy with the evaluations, then breed to a purebred for that 100% Arabian. You can breed those together if you'd like to get a better resulting [+1] if your 100% Arabians aren't perfect. You're aiming for a 4* or 5* evaluation. They're likely going to look a bit odd visually; they might end up looking like dachshunds. That's alright; you'll get the result you need for that elusive horse, so visual appearance doesn't matter.
If you were paying attention to the evaluations throughout this process, then you'll probably have at least one decent Arabian that you can use for the Spiti breed. This is the Spiti that I managed to make via this process. This is the Arabian that I used; he's a 4* Spiti. You can look into his pedigree if you'd like to see the generational changes that I went through to make him. He ended up being around 60% COI, and if I'd been more careful with his ancestry that definitely could've been a much lower number. He also has a good HGP.
You might have to do this with both sides of your new breed's equation. As this is a lengthy process, it's important that you keep either your 100% horses or your 95% horses to make more so that you don't have to repeat it in the future. If you no longer want your specifically bred horse, then I'd suggest seeking a buyer rather than aging it out as these horses can be very rare and therefore very sought after for the right player.
You can also use this process to simply boost the HGP of a breed or add different colors to a breed that's normally set to one default, such as Tarpans which are normally Bay Duns. Instead of evaluating for a new breed, you'd just evaluate for your base breed.
Hopefully this tutorial/guide made some amount of sense. I know there were some vague points and I'm happy to offer any advice and answer any questions. Thanks for reading!
Before we go into detail about specialized breeding, let's look at the basics of breed creation.
Evaluations: Evaluations tell us how well a horse fits a breed's standards. This is mostly used for making new breeds, but can also be used to keep your herd within the standards of the breed that you're working with. Because it shows a breed's standards, you want to use the evaluation book of your target breed. You can get evaluation books in the Book Store in the Market, and you use them under the Eval tab in a horse's page.
Evaluations show the following physical characteristics of the horse:
Height: How tall a horse is. The unit hh means hands heigh. I believe one hand is thereabouts 4 inches. From what I understand, a real horse above 14.2hh is considered a horse, and one below that is considered a pony. Drafts are around 16hh+.
Build: How light or heavy a horse is. Lighter horses tend to be more of a racing build while heavier horses tend to have more muscle for log pull. This goes via the following scale: Very Light -> Light -> Medium Light -> Medium -> Medium Heavy -> Heavy -> Very Heavy. The game notes that while this is a reference, it's not necessarily required to match for making new breeds. Medium tends to be the middle ground. Anything left of Medium wants to keep going left, and anything right of Medium wants to keep going right. Therefore, Light + Light often makes Very Light, Heavy + Heavy often makes Very Heavy, and Heavy + Light will theoretically be somewhere in the middle.
Body Size: The bulk of a horse. Very light horses like Arabians might have 0% size, whereas heavier breeds like Belgians may have a much higher percentage.
Type: Horse vs. Pony type. Horse type horses will look... like a horse. Pony type horses will be ponies and drafts. This uses the following scale: 100% Horse -> 0% Horse / 0% Pony -> 100% Pony.
Evaluations measure the match to the breed's standard in stars. The scale goes from 5* -> 4* -> 3* -> 2* -> NA. You cannot get a 1* evaluation.
If nothing matches then you get an N/A match, which means the horse will be a terrible choice for breeding the evaluation breed. If you only have one matching attribute, then it will always be worth two stars and will be a poor match. Two matches will be worth three stars, which will be an okay match. Three matches will be worth four stars or a great match, and all four matching is worth five stars, which would be a perfect match.
Please note that terrible, poor, okay, great, and perfect matches are not officially referred to as such; I'm just adding that in to give you a better idea of how the stars correlate in terms of a match for a breed.
Generally you want your eval to be four or more stars, as this will give you a better chance at a quick success. The less stars you have, the less of a probability you'll have of getting a foal of your target breed. At three stars or less, you may end up having your horse nearly or completely retire before you can get that new breed.
Also, because evaluations are incredibly important to breeding, you have to be aware of how different horses will match together. It's better if both are 5* evaluations, but if they're not then you can try to balance it out.
If you have a horse that's too tall for your eval, you can balance it by matching it with a shorter horse that might be either too short for the eval or simply on the lower side of the requirements.
If you're pairing two Light build horses, it's likely that you'll get a Very Light foal rather than a Light foal. Likewise, if you match two Heavy horses, you'll probably get a Very Heavy foal. Medium horses tend to stay Medium when bred together as that's the center of that scale. Therefore, if you have a Light horse and you need a Medium, try mixing with a Heavy horse if possible. If you need a Very Light horse, then using two Lights or a combination of Light and Very Light will work. Very Light + Very Light will likely always result in Very Light. Very Heavy + Very Heavy will likely always make a Very Heavy. Those are the maximums for either side of the scale.
Size has been a bit more unpredictable for me, but it's thereabouts similar. Lower percentages tend to like to stay low, whereas higher percentages like to stay high. I've had a 58% and a 52% make both an 82% foal and a 35% foal. It's a bit random sometimes. My advice would be that anything under 50% will possibly make a lower percent, anything over 50% will probably make a higher percent, and there will always be odd outliers.
As for Type, keep in mind the scale. Horse type goes down to zero, and on the other side of zero is Pony type. Likewise, Pony type goes down to zero, and Horse type's on the other side. The less of a percentage it is, the closer it is to the other type. This is balanceable; using a higher Horse type will lower the Pony type percentage and vice versa. Using two Horse type or two Pony type will boost that type.
Continuing forward. The evaluation is incredibly important, but it's also important that you're using the correct breeds in order to make your target breed. These can be found via the Breeds Wiki. If you click on a horse, then it will tell you the horse's recipe on the right side of the screen (so long as they're not Adoption Centre breeds). 100% recipe horses are ideal, but you can get away with using "Part [breed]" so long as it's the only breed listed. For instance, you could use a Part Tarpan to make an Exmoor, but you cannot use a Part Tarpan x Turkmene to make an Exmoor.
You can also use this amazing collective list made by Silverine. This has a list of all of the breeds in the game in an order that can be used to complete all of the breed quests in the game. This is also a good reference to see what crosses can be used where and how. I highly advise taking a look at their post.
To make a horse breed you'll need at least two horses. Many breeds require crosses between a variety of breeds. Your breed could be as simple as the Akhal-Teke (Arabian X Turkmene) or as complex as the Welsh Mountain Pony ([Thoroughbred X Hackney] X [Exmoor Pony X Arabian]). It's always good to make note of what horses you're going to need to mix in order to reach your two main recipe horses, which you'll then breed together to make your target breed.
Many recipe horses can be found via the public studs, but some are rare enough that you'll have to make them yourself. Take this into account before trying to make a complex horse. If you have to make your own recipe horses then they'll need time to age before they can be used, and the last thing you want is for your horses to retire while you wait for that, or for you to have to freeze things entirely while that happens. Always make or find your recipe horses before you start that breed.
=====================================================================================
So, onto the main part. Specialized Breeding in this case would be taking a breed and altering it to fit into a certain evaluation. There's multiple instances where the normal build of a breed really doesn't fit into a recipe that it's used in. Since you want a 4*-5* eval for both horses, this can be an issue.
I'll use Arabians as an example, but feel free to substitute any breed that you want.
The base evaluation for an Arabian horse is as follows:
Height: 14.0hh to 15.3hh
Build: Very Light to Light
Body Size: 0% to 20%
Type: 100% to 78% Horse Type
As you can see, Arabians are a very lightly built horse breed. They're on the extreme side of light. As an Adoption Centre breed, they're also one of the base horses and are used to create a multitude of new breeds.
This becomes an issue when we have a heavy built pony breed requiring Arabians that we have to make. Ergo, specialized breeding must take place in order to make Arabians fit the needs of the new breed. I'll use Spiti as an example, as I've successfully bred one of these myself via this method.
Spiti horses are as follows:
Height: 11.0hh to 13.1hh
Build: Medium Light to Medium Heavy
Body Size: 35% to 60%
Type: 65% Horse Type to 70% Pony Type
As you can see, the Spiti evaluation is very different to the Arabian one. Spiti are shorter, heavier, bulkier, and much more Pony type.
Spiti are made by crossing an Arabian and a Tibetan Pony. We already know the Arabian evaluation, so here's the Tibetan one for reference:
Height: 10.3hh to 13.0hh
Build: Medium Light to Medium
Body Size: 40% to 60%
Type: 70% Horse Type to 60% Pony Type
Tibetans can certainly offer a fair deal of balancing for this recipe. They tend to be shorter, which can counteract the fact that the current non-AC Arabians are rather tall, some being upwards of 18hh. They're heavier built, so it could be possible to reach the Medium Light side of the build requirement... if the odds are in your favor. The Size is 40-60, but as Arabians are 0-20 that might be a hard balance unless you manage to get a 20% Arabian and a 60% Tibetan. Type isn't bad, but you must remember that Arabians can go up to 100% Horse type, which is a hard balance to reach re maximum of 65% when your Tibetans might end up being their maximum 70% Horse Type.
So, how do we fix this?
My answer would be cross breeding the problem breed (Arabians in this case). I don't believe that there's naturally an AC Arabian that's outside of a 5* Arabian evaluation. As such, we can't really make a heavier Arabian just from breeding Arabians together. We'll have to take a heavier breed, mix it with an Arabian, and then breed that cross back to pure while keeping our desired characteristics. The horse doesn't have to eval to a 5* Arabian, after all, just a high star Spiti.
This will take time to do, and require a fair amount of room, but I find that it's very much worth it for the end result.
From the Adoption Centre we get these breeds:
Arabian, Belgian, Caspian, Forest Horse, North African Barb, Przewalski Horse, Shetland Pony, Tarpan, and Turkmene.
If we want to keep a higher HGP, then the best horses to use when altering builds would probably be Arabians, Belgians, and North African Barbs. These are breeds that have had a lot of work put into them, and therefore are often higher quality and better established than the other listed breeds. There are exceptional horses in each breed, of course, but to my knowledge these three are generally the most established of the base breeds.
Arabians, as already stated, are on the extreme side of light horse type. You'll use these if you're making a heavy breed lighter and more Horse type.
Belgians are more on the extreme heavy pony type side. You'll use these as well as Shetlands to make your breed heavier and Pony type.
North African Barbs also tend to be light horse type, but not as extremely as Arabians. You can find Medium Light and Medium NABs, whereas you're unlikely to find Medium (Light) Arabians. You'll likely use these for a less extreme light type.
You can also use non-AC breeds if you'd like such as Thoroughbreds and Quarter Horses, just take note of their evaluation stats so that you know how they'll impact your breed.
In this case, we can use Belgians and NABs to get a heavier, bulkier Arabian. I personally chose Belgians as they're Pony type, bulkier, and a heavier build. The only issue is they're much taller than the Spiti evaluation. To fix this we can cross in some Shetland blood; Shetlands are also heavy, bulky, and Pony type, they're just much smaller and might not have HGP to the standard of Belgians. You'll find that Shetlands and Belgians will probably have a 4* evaluation for each other, the odd part out being height of course. If HGP is a worry for you, then I suggest using high HGP Arabians to counter the lower HGP Shetlands that you might find.
The plan will be to breed your Arabians with a Belgian and/or Shetland until you get a decent foal. You'll then breed that foal to an Arabian upon breeding age until you get another decent foal, and you'll repeat that until you have a 100% Arabian. You can certainly use Grade horses instead of Belgians or Shetlands and stop when the breed reads as "Part Arabian", but I'll be typing this as if you're using a purebred Belgian/Shetland and therefore I'll be referencing "Arabian x Belgian [50%]" and such.
Let's go into more detail now.
To start with, you'll have to pick out your founding Arabian(s) for this project. The number you choose will depend on the amount of room you have. Keep in mind that you'll be going through multiple generations of horses to create your target Arabian.
To be more exact, you'll be making a 50% Arabian, an 80% Arabian, and a 95% Arabian before you hit that 100% goal. You'll probably have more than one 50% Arabian, more than one 80% Arabian, and more than one 95% Arabian. You'll also be breeding together 50% Arabians and 80% Arabians to try to get better evaluations. Expect to use at least one barn for the Broodmares, one barn for the Studs, two pastures for the foals, and at least one pasture for aging out horses.
If you're limited in space due to your max horse limit (which can be increased via player skills) then consider starting with only two Arabians. I'd suggest using mares. You'll want to choose Arabians that have high HGP (if that matters to you), are Light rather than Very Light (if you can find them), and are as high as you can find for Size. These won't overall play a large part later, but it makes changes happen much more easily than taking that extremely light, 0% bulk Arabian as your founder.
Next, find your studs. You can use your own, or use public studs. Assuming you're starting with two mares, I'd suggest breeding one to a Belgian and the other to a Shetland. This will give you two height extremes; the Belgians will be tall and the Shetlands will be short. Swap out with what studs you use if you're worried about COI; you'll be breeding foals together a lot.
Then you wait. Eventually those mares will have their foals. When they do, evaluate those foals for Spiti and see what their statistics are. In an ideal world, you'll get some good matches; however, this can often be difficult. Don't immediately rehome any horses that are poor matches.
You're going to want to breed your 50% Arabians together in order to get better results if the foals you're getting aren't ideal.
Be picky at this stage. I suggest putting down their evaluations and HGP in their descriptions so that you can immediately know what horse would pair best with another. I do this with my Tarpans if you want an example. Those are evaluated for Mongolians.
You want to go for the extreme heavy/bulky/pony side here to balance the extremely light/thin/horse Arabians. See if you can't get any Heavy or Very Heavy 50% Arabians; if you can, then aim for type next and get some Heavy, Pony type Arabians. Then you can try for bulk if you'd like. If they're too Heavy/Bulky/Pony for the Spiti eval then that's 100% alright. Matching them with Pure Arabians is going to lower them back down. Just remember not to breed siblings or half-siblings if you're worried about COI. You can easily keep below a 30% COI if you're careful enough and have enough genetic variance.
Also, as a note: breeding an Arabian x Belgian [50%] to an Arabian x Shetland [50%] will leave you with a Half Arabian [50%] if you're not looking to try for a 100% Arabian and are instead trying for a Part Arabian. So long as the percentages match, you shouldn't get a Grade Horse.
Keep breeding your crosses until you get a foal that you like, then let the foal age to breeding age. At this point you want to breed that foal to another purebred Arabian. You can use one of your mares if the foal is a colt and you don't care about COI (else get a new, unrelated mare at this point and move the others to your age-out pasture), or you can use an Arabian stud if it's a mare. The resulting foals will now be 80% Arabians. You can keep going with your 50% crosses to make more 80%s until you're happy with the variety, then move your 50% crosses to your age-out pasture (or rehome them if they didn't end up having foals).
At this point you want to begin narrowing down to a 4* or 5* evaluation. Repeat what you did with the 50% Arabians; breed those 80% foals together until you get something good, then age that foal and breed it to a purebred. The resulting foal will now be 95% Arabian. Freeze it if you don't have a good selection of this generation yet and keep crossing your 80% Arabians until you do.
If Arabian is the only breed listed, then these foals can be used for breeding your Spiti. You only need a Part Arabian for breeding new breeds. If Belgian or Shetland is still listed, then you'll have to breed to a purebred again in order to get a 100% Arabian.
Again, breed your 95% Arabians until you're happy with the evaluations, then breed to a purebred for that 100% Arabian. You can breed those together if you'd like to get a better resulting [+1] if your 100% Arabians aren't perfect. You're aiming for a 4* or 5* evaluation. They're likely going to look a bit odd visually; they might end up looking like dachshunds. That's alright; you'll get the result you need for that elusive horse, so visual appearance doesn't matter.
If you were paying attention to the evaluations throughout this process, then you'll probably have at least one decent Arabian that you can use for the Spiti breed. This is the Spiti that I managed to make via this process. This is the Arabian that I used; he's a 4* Spiti. You can look into his pedigree if you'd like to see the generational changes that I went through to make him. He ended up being around 60% COI, and if I'd been more careful with his ancestry that definitely could've been a much lower number. He also has a good HGP.
You might have to do this with both sides of your new breed's equation. As this is a lengthy process, it's important that you keep either your 100% horses or your 95% horses to make more so that you don't have to repeat it in the future. If you no longer want your specifically bred horse, then I'd suggest seeking a buyer rather than aging it out as these horses can be very rare and therefore very sought after for the right player.
You can also use this process to simply boost the HGP of a breed or add different colors to a breed that's normally set to one default, such as Tarpans which are normally Bay Duns. Instead of evaluating for a new breed, you'd just evaluate for your base breed.
Hopefully this tutorial/guide made some amount of sense. I know there were some vague points and I'm happy to offer any advice and answer any questions. Thanks for reading!
