Put the summary of the bug you're having here
What I expected to happen was...:
I thought the cow would simply walk away
What actually happened was...:
minecraft simply closed with the crash report when i looked to a cow and a skeleton near it
Steps to Reproduce:
1.i made a trade with a villager
2. looked to a cow in the window
3. apparently there was a skeleton near it and then crashed
Remove your JVM Arguments, as you're only assigning 512MB RAM to Minecraft (as far as I can see, your system can handle more).