plants vs animals

i get a weekly newsletter from the christian vegetarian association.  today's email was particularly interesting (i.e. why you should eat veggies instead of meat based on the math)!  however, i still want to have pet large animals!  they make great compost for a garden.

here is what it said:

In my local area I've been encountering quite a bit of pushback from people who claim that dependence on plant-based foods such as grains and seeds results in exacerbated land use and the collateral killing of many more animals than if we relied on pasture-raised livestock.

I did some calculations on land use efficiency using figures obtained by doing a Google search of Extension Offices and organic farmers:

Pasture-fed "beef" cows who can be raised on 1 acre per year:
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Number of acres needed to raise 1 "beef" cow/heifer = 2 (a very liberal estimate)
Pounds of meat obtained from 1 "beef" cow/heifer = 600
Calories per pound of meat = 800
Calories from meat per acre = 240,000 (800 x 600 / 2)

Sample combination of food crops that can be grown on 1 acre (divided equally) per year:
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5,000 lbs carrots AND 4,000 lbs potatoes AND 1,000 pounds wheat AND 4,000 lbs winter squash
Calorie value of those food crops:
carrots = 180 calories/lb = 900,000 calories per 0.25 acres
potatoes = 400 calories/lb = 1,600,000 calories per 0.25 acres
wheat = 1400 calories/lb = 1,400,000 calories per 0.25 acres
winter squash = 180 calories/lb = 720,000 calories per 0.25 acres
Total calories from food crops per acre = 4,620,000

Number of persons who could be fed in one year with one acre (assuming 2,100 calories per day):
With meat calories = 0.3 persons
With food crop calories = 6 persons

Land use-efficiency of food crops over livestock = 19 times more efficient

I suppose the production of meat could be made more efficient by raising different animals instead of just "beef" cattle. Allowing for that, suppose we double the efficiency of producing meat. That still leaves plant-based food crops at about 10x the efficiency of meat production.

-Stephen Augustine