Take your .270. It will be great on pigs and donkey. As others have stated, donkeys can take some serious punch. They tend to absorb the shock of a chest/shoulder hit and appear to get better as time goes on. I took a number with my .300 Weatherby Magnum last year and whilst some of them went down quickly most absorbed the hit, waited a short while and continued walking on. Head shots of course are a different thing altogether. Have fun...