Quote:
Originally Posted by (E)
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One stock unit equals the amount of food required for a ewe with a single lamb during the slowest growing period of the year.
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Interesting, and it definitely indicates the primary form of livestock in your area.
In North America, we use what is called an "Animal Unit" (AU), which is defined as a 1000-lb beef cow (454 kg) with or without a nursing calf.
We also use a measure, "AUM" (Animal Unit per Month) to describe grazing quality.
Everything else is measured from those two basic units. So, a mature horse is 1.20 AU; a mature pig is 0.25 AU; a mature ewe is 0.20 AU; a mature goat is 0.10 AU.
So, here in Colorado (where I learned
way too much about this, about 22-23 years ago...), a pasture produces (on the average) of about 1,600 lbs (726 kg) of forage, per acre.
A 1,000 lb (454 kg) cow needs 800 lbs (363 kg) of forage available per grazing, each month. So, in Colorado, (given that you need to keep half the forage intact, so as to regenerate the pasture in 30 days or so...), one AU needs one acre of dry-land pasture, at least -- if you're a little lucky.
This can vary widely, throughout the state. Out in the semi-arid, short-grass prairie of northeastern Colorado, it can drop as low as 300 lbs (136 kg) per acre once you get away from the Platte River -- and few people bother to graze. They use hay and silage maize in feed-lots.
Up in the mountains, the forage quality is actually really good -- it's just that there aren't very many flat bits, and the grazing season is really short. A lot of the field acreage in the mountain "parks" is used for hay -- which sells really well, here.
By comparison, the forage quality in Kentucky, where I spent my childhood, comes in at about 1,700 lbs (771 kg) per acre for tall fescue, consistently and reliably, if you do absolutely nothing to it.
Hit it with 90 lbs of nitrate fertilizer per acre, and those yields double. So, if you graze at the recommended 50 percent, and rotate the stock every week or so, you can raise
twice the AU (plus a bit) on the same acreage.