– Rory Lewandowski, Extension Educator, Athens County, Buckeye Hills EERA
The goal of managing a rotational grazing system is to keep the pasture forage plants healthy and growing so that grazing livestock can meet their nutritional needs by eating those plants. This goal is accomplished by adhering to some general grazing principles within a context of understanding an animal’s nutrient needs. The summer months of July and August typically are months of hot temperatures and limited rainfall. Let’s examine some specific management decisions required by summer conditions.
There are two general grazing principles to keep in mind; residual leaf cover, the take half, leave half rule, and second, provide a rest period until the plant is ready to be grazed again. Specifically, in the summer, do not graze pasture grasses below 4 inches in height. Keeping some leaf cover will result in quicker plant recovery after a grazing pass. The leaves will provide some shading of the soil, helping to keep the soil cooler and more conducive to cool season grass growth. Shading the soil from the sun will also conserve moisture, and provide better regrowth conditions. In the summer the rotation through pasture paddocks must slow down. Cool season grasses grow slower under summer temperatures. More time is needed for the grass to re-grow to grazing height after a grazing pass. Specifically, allow the pasture sward to regrow to an 8 to 10 inch height before entering a pasture paddock for another grazing pass.
The application of these grazing principles requires an adequate number of pasture divisions or paddocks. What is an adequate number? In our beginning level grazing school we teach that the number of paddocks needed is determined by this formula: # of paddocks = Rest period/Grazing days + 1. The rest period during a typical summer can vary from 30 days in early summer or if temperatures do not exceed the mid 80’s and some timely rains continue, to 45 or 50 days when temperatures are in the 90’s and rains are few and far between. In the case of a drought, the required rest period can be 60 days plus. The amount of grazing days spent in the paddock depends upon several factors, including stocking density and grass regrowth.
If stocking density is light, more days can be spent in a paddock, but there is a high amount of selective grazing and at some point desirable plants that are beginning to regrow can get grazed again. From a plant health and productivity standpoint, plants should not be grazed again as they begin growth following a grazing pass. So, grazing management will dictate that the time it takes a plant to begin active regrowth after being grazed determines the grazing days part of this formula. In the summer, it is generally accepted that plants do not begin active regrowth until about 4-5 days after a grazing pass.
Alright, back to determining an adequate paddock number. We will use as bookends, a favorable grass growing scenario and a drought condition. Under favorable summer conditions assume a rest period of 30 days with a 4 day grazing period per paddock and under drought conditions assume a rest period of 60 days with a 5 day grazing period per paddock. Plugging these values into our formula says that we will need between (30/4) + 1 and (60/5) + 1 or 8 to 13 paddocks to manage our summer conditions. In other words, 8 to 13 paddocks are needed to allow the grazier to make management decisions that prevent pasture plants from being overgrazed, and to allow pasture plants a long enough rest period to regrow to proper grazing height.
Pasture paddocks do not have to be made with permanent fencing. Paddocks can be made with a single strand of high tensile wire that is electrified for cattle, and electro-netting can be used to make temporary pasture divisions for sheep and goats. The important concept is that more pasture divisions allow the grazier to put into practice management principles and utilize management skills. I have yet to hear a serious grazier say that they regret using or putting in more pasture divisions.