Cattle produce, typically, 48 kilograms of methane each per year.  More
bubbles out of the animalsž manure. "Beef is a greenhouse-intensive
food." Susan Subak of University College Londonžs Centre for Social and
Economic Research and the Global Environment. New Scientist ‚ page 5 -
31.8.96

One cow produces 40 litres of slurry a day.     The Guardian 17.9.97

Flatulent cows and sheep are one of Europežs biggest sources of
greenhouse gases according to a report by EU Commission.  Eructating
livestock and their dung produce 10 million tons of methane, nearly half
the EUžs annual emissions of a gas second only to carbon dioxide in its
contribution to global warming.     The Guardian 23.11.96

US produce 250 million tonnes, half the worldžs corn crop.  80%
exported, much for livestock.   Guardian 22.8.96

Cattle: it takes 100,000 litres of water to produce one kilo of beef.
(Potatoes take 500, soya 2000). New Scientist 1.2.97

Worth reading Jeremy Rifkin.  On water pollution. I have a quote "Cattle
and other livestock account for twice the amount of pollutants as come
from all US industrial sources." (haven't the source but  no doubt in
one of his excellent books or articles)

Another interesting take on this: "Milk is a very strong pollutant: it
is about 400 times more polluting than untreated sewage.  To put it
another way, 1,000 gallons of milk has the same polluting potential as
the untreated sewage from a town of 7,000 people." Morlais Owen.  Chief
Scientist for Welsh Water.  North Wales Weekly News. 24.3.88.

I assume you can translate this to the US too: The rivers of England and
Wales became steadily dirtier over the past decade, a detailed survey by
the National Rivers Authority has found. Sewage works, farming and
drought, rather than industry were mainly to blame.  12.12.91

At an international conference in Beijing it was concluded that the
world must act to avert a water crisis, a senior United Nations official
said. Some 80 countries and 40% of the worldžs people are experiencing
"water stress", Dr Wally NžDow said. The world water supply was expected
to be seriously stretched within 15 to 20 years he added.  Reuters in
the Guardian 22.3.96

When you think how much water is polluted by accidents of slurry,
pesticide residues, silage seepage etc polluting our water ways; plus
all the millions off litres needed to clean up the dairy unit,
slaughterhouse and trucks carrying the animals, let alone the water used
to grow the animal feed and for the animals to drink this meat
production is getting out of hand!

Then there is the amount of medicine given "food" animals. Certainly in
the UK, according to a report put out by the Soil Association (the voice
of the British organic farming movement) at least three fifths of all
antibiotics are used to treat animals rather than human beings.  The
Times 7.12.98