How would that work? It's pretty well known that to cook a steak, you need to hit it with enough heat to operate a blast furnace. Minecraft animals are pretty durable.
Fire a Maser beam - a microwave laser. Certain frequencies of that would very effectively destroy organics without seriously impacting metals or silicates.
In fact, the US military already uses a wide-beam version of it to disperse crowds by making them think they're on fire.