There is a quote in the 1922 U.S. Department of Agriculture Yearbook of Agriculture that is appropriate, “The cheapest of all feed is pasture because it furnishes a balanced ration at a low cost and the cow does her own harvesting … but in comparatively few cases is the fullest possible use made of pasture.”
There is currently a lot of interest in improved grazing management; that’s nothing new as the referenced quote indicates, and it has certainly been the case for the past 30 years.
Rotational grazing provides plants within pastures rest from repeated defoliation by grazers by separating the entire pasture unit into several paddocks. Paddocks are grazed in turn, and livestock are moved on to the next paddock. Grazing is prohibited on the most recent paddock until the next grazing event in the cycle. Those systems can be simple with weekly rotations or complex with daily rotations. A recommendation is to have at least four paddocks with seven-day grazing events and 21-day rests for each grazing cycle to receive many of the benefits from rotational grazing. However some producers have 30 paddocks and rotate large herds of more than 200 cows daily.
Cattle grazing a single pasture at a moderate stocking rate have the advantage of being able to select their diet from every plant from the entire grazing area. That can lead to improved performance because diet quality, protein and digestible energy can be maximized by the grazing animal because there are few limits to their diet selection. When pastures are split into multiple paddocks access is limited to preferred areas, plant species or plants, which will limit intake, selectivity and performance. That is until the most desired plants in continuously grazed pastures are over-utilized and die out of the stand. Recent research was conducted looking at the impact of grazing management -- continuous vs. rotational grazing -- on stand counts of alfalfa interseeded into bermudagrass, and after three years alfalfa was 25 percent of the stand in rotationally grazed pastures but only 10 percent in continuous pastures.
It is often said that continuous grazing can lead to pastures that are overgrazed, yet underutilized. Continuous grazing leads to poor utilization of forage, fertilization and land resources; estimated utilization of forage in continuous grazing is 25 percent to 35 percent. Rotational grazing increases grazing efficiency to 65 percent in well-managed controlled-grazing rotations. That’s why it is often said that stocking rates can be doubled with rotational grazing.
Another grazing experiment looked at continuous or rotational grazing of spring calving cows on bermudagrass pastures. Continuous grazed pastures were stocked at a moderate stocking rate, while rotationally grazed pastures were stocked at either a moderate or at double the moderate stocking rate. Pregnancy rates were not impacted by grazing management or the increased stocking rate, but cows lost more weight and body condition with high stocking rates in rotational grazing. Calf weaning weights were greatest with continuous grazing and were reduced by 20 pounds in moderately stocked rotationally grazed pastures. Doubling the stocking rate with rotational grazing reduced weaning weights by 38 pounds comparted to continuous grazing but increased total weaning weight per acre by 185 percent. Additionally hay requirements were reduced by 60 percent to 80 percent with rotational grazing.
There are costs associated with rotational grazing such as fencing, development of water resources and possibility of reduced animal performance, but there are also many advantages. Increased forage utilization with improved retention of desired forage species, potential increased total productivity of the ranch and reduced drought risk are only a few.
Paul Beck is a beef-cattle nutrition specialist for the Oklahoma State University-Extension.