Agriculture Reference
In-Depth Information
Anyone who has kept a dairy cow cannot fail to have marvelled at the way she can graze
on the grass that we tread underfoot and turn it overnight into prodigious quantities of milk,
which within an hour or two can yield butter. How can solid fat be created so fast from
such an unpromising material? What machine could do the same? Attempts to extract ed-
ible substances from grass and weeds with machines have so far only produced an unap-
petising gunge which requires mixing with sweeteners and nuts to make it palatable.
Despite the fact that she is dealing with such fibrous material, the cow does this both
willingly and surprisingly efficiently, given that (unlike a machine) she is also keeping her-
self alive and having offspring at the same time. In a survey carried out on dairy cows in
New York State, about 60 kg of protein was produced from 190 kg of vegetable protein, a
conversion rate of just over 3:1. Of the 190 kg of protein, about half was from grains and
about half from forage. If the forage was grass from land that could not reasonably be cul-
tivated, then the protein conversion rate of potential human feed to dairy produce in this
case was just over 1.5:1.
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The 3:1 ratio seen in New York can also be observed in the performance of British farms.
A typical UK dairy farm, with black and white Holstein cows, produces roughly 7900 litres
of milk per hectare per year, which is about 250 kilos of protein, whereas a hectare of land
put over to winter wheat would produce about 750 kilos of protein - a ratio of 3:1. On an
organic farm the protein ratio is nearer 2:1, because the yield per hectare of organic cows
is about two thirds that of conventional dairy cows, while organic wheat yields are little
more than half those of conventionally grown wheat. In respect of energy the ratio is 5.4:1
on conventional farms (if you don't factor in the fossil fuels required for the fertilizers that
boost the wheat and grass yields) and 3.7:1 on organic.
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However inefficient the conversion ratio of any given animal may be, if if it is grazing
entirely on land which could not otherwise be used for arable production or some other
highly productive activity, then it cannot be said to be detracting from the sum quantity of
nutrients available to the people of the world, but is adding to them. When I kept Jersey
cows, they produced 3500 to 4000 litres of milk per year on a diet consisting of about one
tonne of bought-in organic lucerne, plus hay and pasture. The lucerne, a legume which in-
troduces nitrogen into the ground, would normally be part of a long term arable crop cycle,
and would require less than one tenth of a hectare. The grass and hay took up about one
hectare of permanent pasture/meadow per cow, and some of that hectare was orchard. The-
oretically the grassland could also have been folded into an organic arable cycle, or even
cropped continously with the use of chemical fertilizers; but since it was on a significant
slope there was no economic or ecological incentive to do so. The cows were effectively
fed little or nothing which could have been human food.
The same is true of suckler cows and sheep, which, in the UK, to a very large extent, are
grazed or fed on hay or silage from land which is either unsuitable for arable production,
