trophic level for chickens is iirc 2:1 thus 2 Kilo grain on 1 Kilo meat but for cows you would be about right - it depends on the animal. The thing is that animal feed (like pure grain) has a higher content of fat and Nutrients then the natural diet of animals (say normal grassing) so the trophic level for these diets are different. Its a little bit like humans which have a healthy diet (lots of vegies, 3 to 4 times a weak meat) compared to someone who lives on Fastfood and Softdrinks.
Even different breeds differ in the food-to-meat ratio. Cows like the diary breed "Holstein Cattle" produce less meat per kilo grain then Meat/beef breads "Florida cracker cattle" or "German Angus cattle". For most animals you have to look at the feed the species and the breed to get the correct ratio.
On a more general note, warm blooded animals generally require much more food than cold-blooded ones. Checking on wikipedia, "In general a warm-blooded animal requires 5 to 10 times as much food as a cold-blooded animal of the same size and build, so cold-blooded animals are better at surviving in environments with small amounts of food, such as a desert, or great seasonal variations in food, such as some tropical areas with long dry seasons."
I'm curious to know if biologists have charts for the expected food-mass consumption of an animal with a given size, build and metabolism; if it's a simple enough relationship Toady might be able to make use of it.
