Half and Half

by Dave Pratt

Take half – leave half.  It is probably the most common advice you’ll hear regarding grazing utilization. In my opinion it is bad advice. It was probably the brainchild of someone looking for a one-size-fits-all, easy-to-remember recipe. It may be easy to remember, but this recipe is likely to produce a crummy meal.

What does take half – leave half really mean?  I often joke that grazing all of one plant and not touching the plant next to it is taking half and leaving half.  While it isn’t what the proponents of this rule have in mind, it is often the result we get when stock density is low.

Of course, rather than taking half of the plants, the objective is to take half and leave half of each plant. But how much of the plant is half?  If the grass in a pasture is 12 inches tall, grazing it halfway down to 6 inches is not taking half.  The height:weight relationship varies from species to species and with different growing conditions, but typically, grazing a pasture from 12 inches to 6 inches removes about 20-25% of the forage.  Removing 50% of the forage may mean grazing the pasture down to 2-3 inches.

Here are the problems I have with the take half – leave half rule:

  • Early in the growing season graziers who take half and leave half would find it very difficult to stockpile enough forage to build a significant feed bank for dormant season grazing.  
  • There is a minimum amount of residue that responsible graziers will leave behind to protect the soil.  If take half – leave half applies in a normal year, then in a drought year you’ll need to take less than half to leave that minimum. Of course in a bumper year you’d be able to take more than half and still leave adequate residue.
  • Take half – leave half ignores livestock performance needs.  There may be times when a smart grazier wants to emphasize animal performance (e.g. flushing prior to breeding or promoting rapid gains on stockers). Generally speaking, and everything else being equal, animal performance will improve during any particular graze period by taking less and leaving more than half.  

Take half – leave half is not a one-size-fits-all principle. It is a one-size-doesn’t-fit-very-many-very-well-very-often sound bite that smart graziers ignore.

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