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Management-Intensive Grazing: Forage Allotment

Grazing Efficiency

Not all forage that is produced will make it into the animal.  All forage harvesting systems, including the most intensive MIG system or the most expensive mechanized harvest system, will have some amount of inefficiency or waste.  A good illustration of this is to consider first the most common mechanical methods for harvesting forage: hay, silage, and green-chop.  Even the most careful equipment operator will leave some forage in the field. In fact, harvest losses in these systems may range from 2.5 - 25%.  Of course, storage and feeding losses can add another 5 - 50% toward the inefficiency of the system.

Similarly, not all forage that is produced will be consumed by the grazing animal.  However, it is generally true that the more intensive the grazing system is, the more efficient this consumption will be.  This is summarized in Table 1 where the relative forage use efficiencies of four grazing systems are compared to the three most common mechanical harvest systems.

Table 1. The range in forage use efficiency of selected harvesting methods.
Method
Efficiency*
Grazing
Continuous Stocking
30-40%
Slow Rotation (3-4 paddocks)
50-60%
Moderate Rotation (6-8 paddocks)
60-70%
Strip Grazing
70-80%
Mechanical
Hay
30-70%
Silage
60-85%
Green Chop
70-95%
* Efficiency is defined here as the relative amount of forage production (or that could be produced) that will actually be consumed by the animal.


In order to accurately ration out the available forage to meet the forage requirement of the grazing animals, the forage allotment must be increased to account for the inefficiency of the grazing system. So, for example, if we maintain a continuous stocking rate on one pasture, each 600 lb steer consuming 19.2 lbs of DM per day will need to be allotted 64 lbs of dry forage per day (19.2 lbs of DM per day / 30% Grazing Efficiency = 64.0 lbs of DM per day). If it were a MIG system such as strip grazing where efficiency is drastically increased, the amount allotted may only need to be 27 lbs of dry forage per day (19.2 lbs of DM per day / 70% Grazing Efficiency = 27.4 lbs of DM per day).

This increase efficiency often allows over twice as many head to be carried on a single acre of land.  This is at the root of why MIG systems often exhibit an economic advantage over unmanaged grazing (i.e., continuous stocking). 

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