Losing mobs/items after crashing

My Minecraft app frequently crashes, whether I'm around many mobs or mostly alone. After the crash, when I open my world again, I find that usually I've lost something. I've lost most of my sheep and livestock, as well as a horse and it's saddle and lead. I rarely lose items in my inventory, except for a time I sheared my sheep and lost the wool, but the sheep remained sheared.