Agriculture Reference
In-Depth Information
a limited number of predators and scavengers. There is currently not enough meat around
for every human to eat at the level at which it is currently consumed in the USA and other
wealthy countries.
Even worse, an increasing quantity of the food consumed by cows, pigs, sheep and
poultry consists of grains and pulses - high quality vegetable protein and carbohydrates
which could be consumed directly, and therefore less wastefully, by humans. Since there
are some 800 million malnourished people in the world who do not get enough grain to
eat, let alone meat, food is effectively being taken out of the mouths of these people to feed
to domestic animals for the inefficient nourishment of a much smaller number of wealthy
people.
Rifkin's observation, in the paragraph cited above, that 'between ten and twenty per cent
of the energy that was devoured remains within the tissue of the predator for transfer to the
next stage of the food chain' is a measure of feed effciency. This percentage can also be
expressed as a ratio - the 'feed conversion ratio'. So, for example, 20 per cent is the equi-
valent of 5:1, meaning that five units of nutrition fed to an animal produce only one unit of
nutrition when that animal is eaten as meat.
This seems simple enough, but the matter soon becomes riddled with variables and com-
plexities, such as the following:
(i) Different animals have different digestive systems, and so perform differently from
each other.
(ii) The same animal can perform differently under different circumstances.
(iii) 'Feed' can mean all food ingested by the animal, including grass, tree leaves and
crop residues - or else only the food which could otherwise have been eaten by a
human.
(iv) The feed conversion ratio is expressed in a number of different ways, which em-
ploy different units of measurement, for example:
• protein in the feed compared to protein in the meat;
• energy (calories) in the feed compared to energy in the meat;
• weight of standard feed compared to weight of the live animal;
• weight of standard feed compared to the weight of edible meat in an animal;
• amount of land required to grow a given quantity of vegetable nutrients compared to the amount of land required
to produce meat of the same nutrient value (expressible either as proteins or as calories, or an amalgam of both).
Of these, it is the last that really matters, because land is the limiting factor. If there
were boundless acres of land for everyone, then it would make relatively little difference
to the hungry and poor of the world what the metabolic conversion rate of livestock was.
Unfortunately land is in short supply, or at least subject to strong competing demands, and
the metabolic conversion rates can be helpful, though rarely decisive, in telling us what we
need to know - how frugally or extravagantly land is being farmed. What we are ultimately
