The only breeding thing to watch is inbreeding, it can produce decent horses but normally it is something that does not take needs repeating and usually produces one of those 10/20% potential failures.

I am not sure I understand about the "in breeding".
There is going to be some when you have a "bloodline", but I have also been trying to add in foals from AI studs and also still buy breeding mares at auctions.

In my specific newbie case, I have 2 studs who both performed well in CK tests who get the bulk of the stud work.
I also have a offline champ who did not do well in CK that I breed with about 5 mares a season, and a few of those foals performed well in CK tests, but the hit rate is much less. I am hoping this broaden out the gene pool some.

Anything else I should be doing to guard against "in breeding"?

Basically direct family members so father daughter etc. when you make a pairing like this you get a flashing red indicator to the right of their names in the breeding screen. Don’t press ok too quick as the warning takes a little time to come up, this is the only time I ever do it, basically accidentally. As you start to put your offspring into the barn you need to expand your stud to avoid this and give you options along the same lines. Eventually many of your lines will feature the same horses but just avoid the direct family breeds and check for the warning.

Oh shoot!
I have seen the flashing thing and clicked anyway. I didn't know what it meant.
Thanks! I will look for that.

Is my offline league ruined now because of in breeding? Or would I have just trashed the horses because they looked bad?
Is there a chance that one of these horses, or more, looked good and were kept and are now going to f**k everything up down the road with breeding?
Oh boy...
I might have to go back 2 seasons where I have a save I can revert to.
Of course I didn't save at the start of this season, like I normally do.

I've never noticed the flashing red indicator before. Has this feature ever been discussed before by Mark or anyone else? I'd love an official description by Mark on what it means and its effects.

Yes, I would love the official word on the effect.
Was just checking. I got it for brother and sister from same sire, and sire and his filly, the stud and his mother). Never got it for any unrelated horses, so it definitely is an inbreeding warning.
I went ahead and backtracked the the start of the previous season, because even that season I think I was getting that flashing indicator and did it anyway, not knowing what it meant.

It is a good feature, and who knows it may just be cosmetic for people like me who wouldn't want to do that anyway, but don't always take the time to check.

Sorry to keep at it with the questions and thoughts, but it isn't like anything else is going on at the moment.
So I have been diving deep into breeding, reading everything I can find on the forum.
It seems, at least a few year ago (2019) the consensus was inbreeding wasn't really a problem, and some even claimed they did it a lot, at least at first to get to their 100% potential horse.

I went back and looked at the 1 yo's that came from in breeding in my league, and many were trash, but there are a couple that look pretty good. I guess as long as they aren't genetic ticking time bombs to do damage down the road in the breeding barn I can continue and not go back to an old save and re-do.

What constitute this 100% potential horse? When it first shows up as a yearling, as a 2 year old, as a 3- year old?
What if this 100% POT horse doesn't perform in CK trials? Maybe all of this talk was for offline racing, even though there were several big hitters from online in it.
It seems most of my high bar horses are trash in 2yo CK trials, and my best performers tend to be mediocre looking good horses. i.e. a 80% pot and spd horse will usually be winner while a 90 - 90 horse doesn't even place in the heats.

No it will not ruin everything it will likely have mostly produced bad horses, if the odd keeper has been breed that won’t matter too much. Just try and avoid it going forward.

Sirus if you hover on it, it gives a message I cannot remember exactly what it says but it’s pretty self explanatory. Officially I don’t know what the word is nor have I really analysed the results but I have noticed the breeds tend to fail often as not, if you auto repeat it takes a couple of goes for it to take and the offspring are generally bad.

Potential is the single most important stat or bar and thus 100% is the holy grail, especially if you can achieve it as a 3yo. The early breeding is just people trying to maximise by breeding the 100 you assume they have or know of in the barn to the closest next best thing, in an early game likely the same horses offspring.

End of the day In breeding is something you need to make your own mind up on, I avoid it, I have done so for a long time now but will have done it in the early days I expect. If you ran a poll here I expect you will find people on both sides.

And I don’t think your going to cripple your pool of horses, it is just for me something that has a low probability of success, in my head it just wastes a pairing. And if it gets out of control and your whole breeding program is based on the same horse your only ever going to be as good as that horse and you may have a low rate of success in breeding.

Thanks Githyanki.
I just went ahead and went back to the start of the previous season to eliminate all the inbreeding.
Probably will work out better anyway, because I am getting better at everything, and already things look better.

The pop up warning for me is a little red button that flashes. It is on the very left side of the selection bar when the 2 horses are selected. I hover over it but it doesn't say anything, though it is clearly for inbreeding as it pings on all of that - sister/brother, sire/filly, Dam and her colt stud.

Interesting stuff for sure.

I wish i could trim the fat in my breeding barn with the mares, but it seems just about every time I see a mare that can retire, I look at her offspring tab and she is producing good horses for the most part. LOL. Makes it hard.

Organically trim is how I do it, as new horses drop in I look at the old ones and maybe ditch a few to keep it manageable especially if the horse in question has offspring in the barn and this the line is maintained. I also sweep clear from time to time to remove undesirable characteristics, quirks, the wrong ground, no finish or consistency etc etc

Thanks for cluing me and maybe a lot of others in on it. I may have noticed it before but it never registered with me that it meant something.

I am not getting any text when I hover over it. It shows when the two horses have the same sire or dam but it doesn't show when I match a sire with one of his daughters. Now that's inbreeding and it should show for that too.

I went into the game so that I could take a screenshot of the warning popping up for sire and filly, but indeed you are correct and it does not come up.
I am glad you something about it. Now I only have to check for on thing when trying to avoid inbreeding, but I wish it was also included in the warning.