Shortly after I joined the NRCS about twelve years ago, a retired NRCS Grazing Specialist by the name of Steve Hibinger was assigned to me to “show me the ropes.” One of the things he taught me about grazing in Ohio thas stuck with me all this time. If I could teach it to every livestock producer I work with, it would solve 95% (or more) of their grazing problems. It is four simple rules for grazing cool season grasses that can be explained in just ten minutes to anyone. Here they are:
1. Never graze forages to a height shorter than four inches.
2. Never graze a pasture for longer than seven continuous days.
3. Never return to a pasture to regraze in less than 28 days.
4. Never let seed heads form.
Like I said, short and sweet, and effective. Most guidance I give about grazing is some variation of these rules. Here’s some reasoning behind these.
Rule 1: Never graze forages to a height shorter than four inches.
The first rule is to not graze grasses shorter than four inches. The plant needs to keep enough leaf area “solar panels” that does not have to draw on food reserves it has stored in its crown and roots. Additionally, grazing closer than the four inch residual height is inefficient for livestock and results in reduced intake, which means lower weight gains, which in turn means lower profits. Grazing an actively growing plant closer than four inches will compromise its regrowth ability and lower its vigor. This rule is much the same as the “take half leave half” that often gets applied to pastures, but I think it is much clearer as I always found myself frustrated and asking “Take half and leave half of what?”. The four inch rule is a much clearer standard than half of something that isn’t ever the same.
Exceptions to the Rule:
Grazing closer than four inches can and should be used when broadcasting seed over an existing pasture. The resulting short grass from close grazing promotes better seed to soil contact. The shorter grass height also aids in germination of the broadcast seed and growth of seedlings by allowing light to reach the soil surface.
Rule 2: Never graze a pasture for longer than seven continuous days.
Grass plants begin to regrow about three days after being grazed. After about six days the regrowth is enough that livestock can start getting bites of the new grass. Given a choice, livestock will graze new growth over older, month old growth. Regrazing needs to be avoided if grasses are to recover quickly and be ready for grazing in the next rotation.
If you find yourself saying that there is too much grass to be eaten left in the pasture to be grazed after seven days, the size of the pasture needs to be reduced, or get more livestock. Leaving livestock longer in the pasture will only result in regrazing and damage to already grazed plants before the older, more mature plants are grazed.
Exceptions to the Rule:
The rule of not grazing for more than seven continuous days can be ignored at times when grass is not actively growing, such as during the winter, when selective grazing of regrowth will not occur as there is no regrowth to graze. For example, strip grazing stockpiled forage by moving a “front wire” forward without a “back wire” to allow access to a water source.
Rule 3: Never return to a pasture to regraze in less than 28 days.
The rest period of 28 days between grazing is probably the most important yet least considered in grazing rotations. The rest allows the grass plant to recover and be ready to graze again. Returning to the pasture too soon can slow plant growth, decrease plant vigor as well as cause root death. Producers are often told that the need to graze their pasture within a set period of time or to a certain forage height but are rarely told that they need to have a set time interval of rest between grazing for grass to recover. This is the most common error I have encountered when and where grazing rotations are designed.
Exceptions to the Rule:
In addition to being the most important of the four “Never-Fail” rules, the rest period rule is probably the rule where an exception will occur most often. When grass is growing rapidly in the spring, a shorter rest interval, as short as eighteen days, can be observed or may have to be observed to prevent seed head formation. Conversely, during a summer slump or drought, a longer recovery period for grasses may be required.
Rule 4: Never let seed heads form.
Some livestock producers may argue with me on this last rule and say that seed heads are a good thing. The question for all of us then is are we trying to produce seed to get more plants, or do we want to produce as much high-quality forage as we can?
Removing seed heads from grasses by grazing or mowing serves to keep the plant in a vegetative and actively growing state. When seeds form on a grass plant, a hormone in the seed head is transmitted to the rest of the plant that essentially tells the plant “Hey, you have produced seed this year, you can stop growing”. If you are trying to produce forage, you don’t want the grass plant to get this message.
That being said about, maybe there is a need to reseed the pasture. In this case, we need to ask ourselves if the loss of potential forage and the risk of poor seed production outweigh the benefits of purchasing quality seed and mechanically reseeding the pasture.
I routinely meet with livestock producers to discuss and design grazing management plans, often for several hours. However, time and time again I find myself emphasizing these four “Never-Fail” rules as the basis for decisions the producer has to make about his or her grazing operation. I think they could work for you too!