Apart from when I had several waves of wild rhesus macaques invading my space (through the middle of my 12x12-or-so pastureland, it and my main entrance bordered by a multi-Z ditch, except for the necessary bridges to traverse entrance->pasture->wilds across the ditches for work purposes) a recent fort (that I'm ditching (NPI!) for a re-attempt under .21) had absolutely no combats, despite having over the first three years imported more grazing animals than the pasture could apparently support and ending up with at least one starved-to-death bull, in amongst the mess of happily breeding (and some starving) alpacas, sheep, geese, blue peabirds, etc, etc...
In fact, the only combat reports I got were of the likes of gosling vs macaque (creating a heavily injured gosling, but didn't die), blue peacock and macaque (more injuries, and then it got inadvertently stuck on top of my windmill-tower that I built so as at be able to place the lever-controlled gear to the underling pump at ground level, apparently didn't want to fly down after I removed the ramp) and my tame Cougar (good enough not to eat my goslings, peachicks, lambs, yak calves, etc, etc, etc) causing the macaque troop a few fatalities prior to my fledgling military finally getting to grips with them.
Except for one report. Immediately upon embark the two wagon-towing beasts (I think yak was one, can't remember what the other was, but another cattle-type... leastwise, the two beasts that I had most certainly not shelled out good points for in my embarkation preparations) had reported a slight scuffle. This was prior to any pasture being made, so must have been because they were sharing the wagon-footprint 'default meeting area', possibly even the very same spot, for just a microsecond longer than one or the other was comfortable with. No permanent injuries from that incident, and it did not reoccur, even while I was still unsure about the process of pasturification. Possibly they just wandered off to opposite sides of the cart, but I was too busy to keep track of them, at that point...