After I wrote my blog in August about confusion over the relationship between stock density and grazing time, my friend Steve Freeman from Missouri wrote to tell me he hears as much confusion over stocking rate and stock density.
I agree and so decided to address it briefly here.
Stocking rate is the same thing it has always been. It attempts to match the productive capacity of the land with the consumptive needs of the livestock.
It is a year-long measure of how much livestock the land can support. In most cases stocking rate is stated as the number of acres per cow unit or per steer, such as the pasture where I live typically has a stocking rate of 10 acres to the cow unit. That cow unit really hasn't changed, either, and is still considered to be a 1,000-pound cow with calf at side part of the year.
Stock density, on the other hand, is just a measurement of how much weight of livestock is present on a given area at any given time.
Under continuous grazing the term would not even be used. Quite simply if you had 16 dry cows that each weighed 1,000 pounds on 160 acres near my home in north-central Oklahoma you would have a stock density of 100 pounds per acre. That is 1,000 X 16 = 16,000 total pounds, divided by 160 acres = 100 pounds.
On the other hand, if you had 20 paddocks on that 160 acres with an average paddock size of 8 acres, those 16 dry cows would give you an average stock density of 8,000 pounds per acre. If you had 100 paddocks of 1.6 acres each, those 16 dry cows would represent 10,000 pounds of stock density on each of those paddocks.
If 15 of them had 400-pound calves at side you would add that amount to the stock density at that time. So add 6,000 pounds to the 16,000 for the cows and you would have 22,000 pounds of stock in each of those 1.6-acre paddocks. That would be a stock density of 13,750 pounds per acre. However, they would still have a stocking rate of 10 acres to the cow unit for the year.
The reason for figuring stock density is because it tells us several things, particularly in relation to discovering higher stock densities.
1. It implies shorter graze periods and longer rest periods, as I explained in that August blog.
2. It suggests much more density of hoof action on the soil and plant life and much better distribution of urine and dung across all the land.
3. It nearly always creates more competitiveness in forage consumption by the cattle and higher grazing efficiency, so the forage you have should go further, even without stressing the cattle and "making them eat it."
4. If done as part of well-executed grazing management, it implies the manager would see more rapid improvement in the forage and land.
So put in simple terms, stocking rate is just a measure of the land's carrying capacity. Stock density is the amount of stock present on the land at any given time and is really an indicator of management technique.