And myself and some other folks in this area - the minis (or smaller equine) have been the cause of euthanizing "biggies" due to aggressive attacks breaking legs that weren't repairable.
That said, I don't have true minis (under 34") other than some of our weanlings and it's been VERY rare to turn weanlings out with the larger horses once we moved to a property that we did or needed to separate the "littles" from the "bigs".
Keep in mind that there are also individual personalities. There are just as many small equine whom don't get along as there are big equine and that has to be accounted for as well. Our pastures have "changed" off and on due to that aspect - I've never kept all the pastures the same week after week, month after month or year after year.
I do now try to keep the boys together and have the "Sr mares" and the "Jr mares" together in different paddocks. BUT have some issues right now with a few of the "Jr mares" - So will be getting up some fencing in an area hadn't planned on fencing yet so that we can go back to free feeding alfalfa pellets to get them back to where they should be in weight before true cold weather hits us. Also, we've had foals at an odd time for us (several haven't arrived yet) and they will be weaned in that same paddock with the 2 yr old fillies and will also be on free feed alfalfa pellets as well.
Last night, the 39" 4 yr old stallion was beating up on the 13.1 hh gelding pretty heavily. It was at feeding time and it mostly consisted of driving him out of the spaces he wanted, but I did keep an eye on it while I was out in each individual area. But then again, usually the stallion goes right into his own pen - last night he didn't (and neither did the two geldings he was chasing around). None of the three ate - I no longer play the "corner and chase" game - each of these ponies knows the feed drill and have for years. Usually the boys are the BEST - they go stand at their gates and/or their buckets and they are the first to be fed and then turned back out. NOT LAST NIGHT...
Figured it was due to the changing weather and the HUGE drop in barometric pressure yesterday afternoon. It hit 90* + yesterday, then dropped to 45* as of 0530 this morning... With the rain last week, the sand sprouted some type of grass they've all gone crazy on it, plus the boys have 10 round bales in their pasture, none are underweight or even extra light anymore - so missing a meal sure won't "kill" them...