The "vegan" pseudo-argument on "inefficiency" is that
the resources used to produce a given amount of meat
could produce a much greater amount of vegetable food
for direct human consumption, due to the loss of energy
that results from feeding grain and other feeds to
livestock.

In order to examine the efficiency of some process,
there must be agreement on what the end product is
whose efficiency of production you are examining. If
you're looking at the production of consumer
electronics, for example, then the output is
televisions, stereo receivers, DVD players, etc.
Rather obviously, you need to get specific. No
sensible person is going to suggest that we ought to
discontinue the production of television sets, because
they require more resources to produce (which they do),
and produce more DVD players instead. (For the
cave-dwellers, an extremely high quality DVD player may
be bought for under US$100, while a comparable quality
television set is going to cost several hundred
dollars. $500 for a DVD player is astronomical - I'm
not even sure there are any that expensive - while you
can easily pay $3000 or more for a large plasma TV
monitor, which will require a separate TV receiver.)

What are the "vegans" doing with their misuse of
"inefficiency"? They're clearly saying that the end
product whose efficiency of production we want to
consider is "food", i.e., undifferentiated food
calories. Just as clearly, they are wrong. Humans
don't consider all foods equal, and hence equally
substitutable. As in debunking so much of "veganism",
we can see this easily - laughably easily - by
restricting our view to a strictly vegetarian diet,
without introducing meat into the discussion at all.
If "vegans" REALLY were interested in food production
efficiency, they would be advocating the production of
only a very small number of vegetable crops, as it is
obvious that some crops are more efficient to produce -
use less resources per nutritional unit of output -
than others.

But how do "vegans" actually behave? Why, they buy
some fruits and vegetables that are resource-efficient,
and they buy some fruits and vegetables that are
relatively resource-INefficient. You know this by
looking at retail prices: higher priced goods ARE
higher priced because they use more resources to
produce. If "vegans" REALLY were interested in food
production efficiency, they would only be buying the
absolutely cheapest fruit or vegetable for any given
nutritional requirement. This would necessarily mean
there would be ONLY one kind of leafy green vegetable,
one kind of grain, one variety of fruit, and so on.

If "vegans" were to extend this misuse of "efficiency"
into other consumer goods, say clothing, then there
would be only one kind of shoe produced (and thus only
one brand). The same would hold for every conceivable
garment. A button-front shirt with collars costs more
to produce - uses more resources - than does a T-shirt,
so everyone "ought" to wear only T-shirts, if we're
going to focus on the efficiency of shirt production.
You don't "need" any button front shirts, just as you
don't "need" meat. But look in any "vegan's" wardrobe,
and you'll see a variety of different kinds of clothing
(all natural fiber, of course.) "vegans" aren't
advocating that only the most "efficient" clothing be
produced, as their own behavior clearly indicates.

The correct way to analyze efficiency of production is
to focus as narrowly as possible on the end product,
then see if that product can be produced using fewer
resources. It is important to note that the consumer's
view of products as distinct things is crucial. A
radio can be produced far more "efficiently", in terms
of resource use, than a television; but consumers don't
view radios and televisions as generic entertainment
devices.

The critical mistake, the UNBELIEVABLY stupid mistake,
that "vegans" who misconceive of "inefficiency" are
making, is to see "food" as some undifferentiated lump
of calories and other nutritional requirements. Once
one realizes that this is not how ANYONE, including the
"vegans" themselves, views food, then the
"inefficiency" argument against using resources for
meat production falls to the ground.

I hope this helps.