Stocking Rate, Grazing Capacity & Stocking Density
There are various ways of representing figures around stocking livestock on a farm and working out grazing capacity. It is critical to match livestock requirements with available grazing and a close eye must be kept on livestock body condition and dung consistency to check that you are getting this right.
Terminology
- LSU - Large Stock Unit - this is a standardised measure to help with stocking, supplementing and water calculations. A LSU = 450kg of live mass. In most regenerative systems a LSU relates roughly to 1 cow or 6 sheep but weights differ and you need to work it out for each situation. This caters for all classes of livestock from young to adult males.
- SD - Stock Days - this is a measure of how many days of grazing a camp or farm can give 1 LSU per year.
- SDH - Stock Days per Hectare - a measure of grazing capacity
- Herd Impact - the aggregated impacts that a herd of livestock has on the soil-plant ecosystem - grazing, trampling hooves cutting, dung, urine and saliva.
Stocking Rate
Stocking Rate is the most common and widely understood. It is also referred to a Carrying Capacity. It is how many hectares of veld on a certain farm or camp are required to sustainably support 1 LSU for a year. All regions of the country have recommended stocking rates. These are worked out on climate and soil type for conventional grazing in an average rainfall situation. This is how farms are valued for sale.
6 ha/LSU - this means 6 hectares is required for 1 LSU
You can divide the number of hectares of the farm, or a camp, by 6 and work out how many LSU it can carry. A 1000 hectare farm with a Stocking Rate of 6ha/LSU can stock 166 LSU under conventional grazing and average rainfall.
Grazing Capacity
Grazing Capacity is a different way of measuring the grazing you can get from a unit of land. It is measured in SDH - Stock Days per Hectare. It is how many days of grazing a hectare of land can give to an LSU of livestock. This is important in working out grazing budgets and plans. You can work this out from the stocking rate and then by keeping records of Stock Days taken off in each camp develop better budgeting data. As your farm regenerates it produces more biomass which enables you to remove more SDH. It is only possible to use this metric usefully if you keep good grazing records per camp.
25 LSU/ha - this means each hectare of that farm / camp can provide 25 LSU with grazing.
This is calculated by dividing 365 by the Stocking Rate e.g. 365 / 6 = 60.8 SDH.
Rainfall: This data point can be improved by including rainfall data and working out SDH per 100mm of rain.
If you had 600mm of rain that year then it becomes:
- 60.8 x 600 / 100 = 364 SDH/100mm.
If your rainfall is below average you recalculate and it becomes:
- 60.8 x 450 / 100 = 273 SDH/100mm
Stocking Density
Stocking Density is the density at which animals graze during a specified time period, an hour, a day, a week expressed per day. Stock density is very important in creating Herd Impact on the soil-plant ecosystem. The number of LSU on a particular land parcel is divided by the hectares they require to graze for the time period they are on that parcel and then divided by that time period expressed in days. Because it is divided by, divided by the numbers change rapidly when the size of the parcel and/or the number of days on the parcel of land increase. This you can see in the example below.
75 LSU/ha/day - this means grazing happened at an equivalent of 75 LSU of livestock on 1 hectare for 1 day
- 75 / 1 / 1 = 75 LSU/ha/day
If the livestock were on that same parcel of land for 2 days it would be:
- 75 / 1 / 2 = 37.5 LSU/ha/day
If the livestock were on that 2 hectares of land for 2 days it would be:
- 75 / 2 / 2 = 18.75 LSU/ha/day