The typical composition of food for cattle consists of a mixture of corn (wheat, maize, soy and other products (grass, molasses, mineral feed).
Considering that only 60% of the animals' parts (bones, sinews) can be made into usable meat, you will come to the following consumption of food:
Thus, altogether 12 kg of feed are needed for one kilogram of beef on average.
If we return to the example of a 200-gramm-burger, we now know that it was made with 800 g of corn (4kg : 5) and 300 g of soy (1.5 kg : 5).
As it has already been mentioned under Food consumption of animals that these products are ideally suited to be eaten by humans, too. They have a similar protein content, a far higher content of carbohydrates and a far healthier content of fat than meat.
The average calorie content of corn and soy is:
Consequently, the 800 g of corn and the 300 g of soy which are needed for a 200-g-beef- burger contain 4,310 kcal (8 x 370 kcal + 3 x 450 kcal). This corresponds approximately to double the calorific requirement of a fully grown human.
As the amount of feed and the yield of meat differ strongly according to the kind of animals, their husbandry and the composition of the feed, different data are given in the various sources. So the data mentioned here can only be seen as average data.
With pigs, for example, far less feed is needed to produce meat, i.e. 3-6 kg of feed for one kilogram of meat.
But on the other hand, this kind of feed consists to a far larger content of corn and soy (which could also be eaten by humans) and includes no grass. So the energy balance of pork production is similar to the one of beef.