As converters of food, animals are very inefficient! They consume more food than they produce. How much food (calories, protein, and nutrients) is lost from harvest to animals to meat production? What are the consequences for food security, human health, and our planet?
To express the ratio of the volume of feed/crops used to produce one unit of meat, the so-called Feed Conversion Ratio, (FCR) is used. It first provides the following Mainstream Feed Conversion Ratios (middle-range estimates):
Chickens FCR – 2 to 5 (unit feed for one unit meat)
Cows FCR – 6 to 25
Already these – so far imprecise – figures show that chickens utilize crops more efficiently than cows. They have a lower FCR, meaning less feed is needed to produce one unit of chicken meat than one unit of beef. Regrettably, chickens are still very inefficient, consuming more than twice as many calories and protein as they produce.
Most of the energy that animals consume is used for their metabolism and for the formation of bones, cartilage, feathers, fluids, and other non-edible parts. So, the inefficiencies increase when we subtract the weight of water, blood, other body fluids, bones, and other non-consumable body parts. New, more comprehensive methods show that even the peak values of the commonly cited FCRs are very conservative.
Perhaps the most accurate way to measure the inefficiency of animal food production is to calculate the plant biomass that flows into animal production relative to the resulting energy in edible calories in the form of meat, dairy products, and eggs. This method goes beyond the costs associated with an individual animal and instead looks at energy flows in the broader food system.
The inefficiencies determined in this way, are again lower than the FCR values. This is because it also considers the feed that is wasted before it reaches the animals, the plant mass used for purposes other than feed (e.g., bedding, energy from grass and other forages used to feed the animals), the energy needed to support animal production beyond just animal production.
Many animals involved in livestock production do not directly produce food, such as animals that are necessarily culled, die before reaching sexual maturity, and are used for breeding. (Stefan Wirsenius, Human Use of Land and Organic Materials, 2000). According to this study, more than two-thirds of the energy input for plant mass is used for livestock production, but only about 13% of the total food calories can be produced.
In contrast to the FCR method mentioned above, which only considers the conversion of feedstuffs such as soy or corn, here grass and forage are also included in the calculations. This gross energy calculation includes grazing land – the largest source of energy from plant biomass.
This, along with the inherent inefficiencies of feed conversion in cattle, is one of the reasons that beef production is one of the least efficient forms of food production.
NOTE: Grazing cattle is sometimes described as a very environmentally friendly alternative. Unfortunately, grass-fed ruminants (cows, goats, sheep, etc.) are even more harmful in terms of climate change. Grass-fed cattle emit three times more methane than their plant-fed fellows. Much of the pastureland could instead be better used for crop production. Land would be used more efficiently, and the climate could be better protected.
Conclusions
The cultivation and use of crops such as soy, corn, wheat, etc. as animal feed is many times more resource intensive than their direct use for human nutrition. Since about 75% of all agricultural land is currently used for this purpose, accounting for more than one third of the world’s calorie demand and about half of the world’s protein demand, a further increase in meat production would have serious consequences for the climate and food security.
