Journal: Killer Cows

I was reading about a tasting robot that thinks people taste like bacon. The writer comments that robots that get a taste for blood will become killers, just like cows. I've not read of many 'killer cow' incidents. Is this because its not true, or is there a secret military programme to create an army of killer cows? I could imagine the plan to replace all normal cows with 'sleeper' killer cows. This would be especially effective in third world countries where cows are in much closer proximity to the population. Completely stupid or amazingly sneaky?