Feeding grain to animals multiplies the land a food needs: an acre of corn yields 2.5-5.0 million kcal eaten directly, but fed to beef cattle at the caloric guide’s 5-10% efficiency it returns only 125,000-500,000 kcal, so grain-fed beef needs 10 to 20 times the land per calorie. Pasture avoids this only where the land cannot grow crops, because the guide gives no pasture yield to put a number on it.
Part of Caloric Budget for a Community
Pasture-versus-grain calculations compare the human food energy obtained from an animal fed on grown crops with the energy of the same crop eaten directly, and with animals kept on land unfit for crops.
The Land Cost Is Set By The Feed
The caloric guide rules that animals should eat what people cannot, and that at most 10-15% of cropland should go to animal feed grain. This page shows the arithmetic behind that rule using only the guide’s figures.
Worked Example: One Acre Of Corn, Two Routes
Inputs from the guide: corn yields 2.5-5.0 million kcal per acre; beef cattle are 5-10% efficient; meat chickens are 15-20% efficient. These efficiencies are the guide’s stated ones; the feed-to-meat page shows some of them are too high on grain, which would make the penalty larger (Feed-to-Meat Ratios by Animal).
- Eaten directly: 2.5-5.0 million kcal.
- Fed to beef cattle: lowest case 2.5 million × 5% = 125,000 kcal; highest case 5.0 million × 10% = 500,000 kcal.
- The cost of the detour: 1 ÷ 0.10 = 10 times the land per calorie at best, and 1 ÷ 0.05 = 20 times at worst.
- Fed to meat chickens at 15-20%: 2.5 million × 15% = 375,000 kcal up to 5.0 million × 20% = 1.0 million kcal, a land penalty of 1 ÷ 0.20 = 5 to 1 ÷ 0.15 = 6.7 times.
So the penalty ranges from about 5 times for chickens to 20 times for beef when the feed is grain.
Worked Example: The Guide’s Own Feed Grain Allowance
The sample plan for 100 people has cropland in staple grains (25-30 acres), roots (10-15), legumes (8-10), oil crops (3-5) and vegetables (5-8). Summing those parent figures gives 51-68 acres of cropland (25 + 10 + 8 + 3 + 5 = 51; 30 + 15 + 10 + 5 + 8 = 68); this sum is this page’s arithmetic.
- The 10-15% allowance for animal feed grain is 0.10 × 51 = 5.1 acres to 0.15 × 68 = 10.2 acres.
- At corn’s 2.5-5.0 million kcal per acre, that is 5.1 × 2.5 = 12.8 million to 10.2 × 5.0 = 51 million kcal of feed.
- If all of it became chicken meat at 15-20%, the food is 12.8 × 0.15 = 1.9 million to 51 × 0.20 = 10.2 million kcal, about 1.9% to 10% of the community’s 102.2 million kcal a year.
That is what the allowance buys. The rest of the animals’ diet must come from other land.
Pasture: What Can And Cannot Be Said
The sample plan holds 20-30 acres of pasture and hay, out of 91-128 acres in total. The guide gives no forage yield per acre, no stocking rate and no energy for pasture, so the calories obtained per pasture acre cannot be computed from it. The honest statement is qualitative: on land that cannot grow crops, pasture turns grass, which people cannot digest, into milk and meat, and no cropland is displaced. On land that could grow crops, the same acre in pasture displaces the 0.9-5.25 million kcal an acre of the guide’s crops would have given. Pasture management is in Pasture Management, and the feed side in Feeding and Nutrition.
Method: Decide Where Each Animal Eats
Step 1: Map the land by what it can grow (Land Allocation Planning). Step 2: Put grazers on the land that cannot grow crops. Step 3: Cap feed grain at the 10-15% allowance and put it into the animals with the best conversion (the guide ranks chickens for eggs first). Step 4: Measure pasture yield and stocking on your own land, then add the numbers this page cannot supply.
Common Mistakes
- Counting pasture acres as free. They are free only if the land is unfit for crops.
- Feeding grain to the least efficient animal. Beef on grain is the worst conversion in the table.
- Forgetting the transition rules. Switching ruminant feed needs a 10-14 day transition and long-stem fibre, or the animal can suffer acidosis (Feeding and Nutrition).
What’s Next
- Learn next: Dairy and Egg Calorie Efficiency — the animals that give food without slaughter
- Combine with: Acres per Person by Diet Type — the whole-community consequence