I caught a Thoroughbred with just a whistle, I tried the whistle on the next Thoroughbred I came across and it hated it. 

I haven't really learned anything yet but to be fair I haven't been writing my data down, I should be. 

I wish I had thought to start recording data from when I've tried this. So far caught 1, welsh c with just petting an basic treats

I was doing give treat > pet twice > if they respond well to both pets then give treats until you can call them

In my experience with wild horses, every single one has hated the whistle. I haven't attempted to catch many but the ones I am interested in are very anti-whistle.

I've had a range of experiences. Most horses hate the rope, petting and the whistle and I don't have enough treats to try it with every wild horse I come across. I've also had horses like and dislike the same item when I use it again. For ex one horse liked the whistle, then I tried again and it ran away. I think only 1 or 2 wilds had an increased bond from petting. Almost all the horses I encounter are in the red on the 'wildness' scale, so maybe that's why they dislike everything I tried. 

Edit: caught my first wild - a 4* Quarter Horse stallion. Took 15 actions with the last one being a whistle that took the horse from 30% mood to my stables. Trying whistle before that resulted in drop in mood, go figure

I have yet to catch a wild one, I'm still sad over the first wild I saw , that I honestly wanted, a gorgeous black, spotty saddlebred , but he ran off 

I'm not sure if this thread is still being checked by people or not, but I made a lil bit of a discovery (and a theory--) that I wanted to share in case if it wasn't something that some people knew:

The first discovery is it seems like some horses might have certain patterns in order to raise their trust up: I just tamed a horse with a red background for its mood, and its trust meter raised up to 30% (and its moodlet went into orange) when I did the following:
Lasso, pet

But when I went to pet it again, its trust went down again. When I used the lasso and petted it again, its trust went back up to 30% and I was able to whistle it to tame it. With that in mind, I assume it's similar for horses that rely on treats to be tamed. If that's the case, then it might explain why some horses seem totally unobtainable with just a lasso and some pets lmao

Somewhat related to the pattern, my theory is that the whistle is more meant to claim the horse once that horse reaches a certain trust threshold. It doesn't seem to raise up trust any of the times I tried to use it on wild horses, only lower it or claim the horse. And, if you use it one too many times, it seems like it tends to be the one object that will scare a horse off super quick.

I caught my 4* paint mare by just petting. On my first day 💙 I would pet, then wait 3-4 seconds then pet again.

So far, my plan is to feed the horse with treat, pet, and at 75% - 90% use a whistle. All the breeds Ive encountered so far like Welshies A, Irish Cobs, APHs and TWHs responds pretty well to this routine. The only breed that has been pretty frustrating and stubborn so far are the Chincoteague (?) horses, for them I mainly just pet, lasso and pray for the best lol

Whistle is a very powerful item I would recommend, cause from the wilds I've successfully caught (9/18 wilds, basically 50/50 chance), 2/3 of the horses will approach after 1-2 times using whistle. For me, using whistle has a very high success rate, so I would like to see if that also works for you. DON'T USE IT BEFORE 70% THO!!! 70% is the limit I set before using whistles, using it any time before that will decrease bonds. 

Don't use lassos for the red-icon horses. The yellow-green icon ones mostly loves pets and if they reached at least 75%, don't be afraid to use a whistle or click "try to call" if it appears. Carry a TON of treats and food, they're gonna come in handy. 

I've caught two wilds so far (a Welsh and an Irish Draught) and I used similar strategies to catch each.

For the Welsh I pet, treat, pet, treat, etc. I called him when he was at 100% bond (was my first wild and I didn't want to risk losing him haha). Petting increased the bond more than treats, but if I pet twice in a row the bond would go down.

For the Irish Draught I pet and then used treats to get the rest of the way (as I was too low on energy to keep petting). The treats only added a small amount to the percentage (don't remember the amount/treats) and when he was at 95% bond I called him.

I see a lot of wilds that I'll try the whistle or lasso on first and that has never worked for me. I've never tried petting or treating then using the whistle/lasso, I might try that soon.