Allan Savory runs 100 cows on 1acre of land for 24hrs, then he leave and return every 45days.
That works out to be 45acres to feed 100cows for 45days, and that cycle is repeated over and over for as long as the growing season is.
For some folks that is only 90days or 2harvest for others it is 135days or 3harvest.
Interestingly Mob Grazing only require 1/2 an acre per cow throughout the growing season. Obviously during winter hay or something else is needed.
25,000sqft to feed 1000lbs of cow.
Bio-Intensive gives 2,500 to feed 150lbs of human.
Both those numbers are pretty close.
It seems like the pattern is 25sqft to feed 1lbs of animal during the growing season.
Is your intent here just to determine stocking rates for a given size of pasture land?
It's an interesting way of looking at it. Though I'd be cautious as stocking rates, even when just looking at one species, will vary considerably based on the quality of the pasture, rainfall in a given year (assuming no irrigation), capacity to irrigate, and probably a dozen other factors. And, sometimes putting other animals on the land simultaneously (e.g. sheep) or following a few days behind (e.g. chickens) can increase productivity, but not always.
I've done the math on sprouted barley fodder and it comes out to about 8 cows per acre. That's assuming two crops a year and good to great yields. But it's accounting for the entire year not just the growing season.
Also, if feeding comfrey and fall leaves works and well manured comfrey really yields 100 tons to the acre like the book says it does, the potential is huge. Assuming unlimited access to fall leaves and a 50/50 mix that's 400,000 lbs of feed to an acre. 40 lbs per cow per day x 365 = 14,600. 400,000 ÷ 14,600 = 27.4 cows fed per acre.
I've also heard of a permaculture guru (forgot who) saying 10 cows per acre growing hay under nitrogen fixing trees and cutting them for tree hay. I believe it, but cutting all that hay and all those trees seems like more work to me than harvesting barley or comfrey. Although you wouldn't have to use the manure like with comfrey or build a sprouting room like with barley.
Rotational grazing seems like you are sacrificing number of animals fed per land unit for low labor input. Doesn't take long to move electric fence around. But "cut and carry" systems seem more in line with permaculture since they are intensive and better done on smaller pieces of land, but allow you to multiply your relative output vs the guys on hundreds of acres.
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