Many producers that have contact with the Agricultural Division are practitioners of rotational grazing management in various forms. Although they are willing to implement a rotational grazing scheme or a fertility recommendation, few are keeping grazing records that can determine the effectiveness of such recommendations.
What are grazing records? Grazing records are information from grazing events that determine an estimate of forage production.
Why keep grazing records? Grazing records are used to determine the effectiveness/feasibility of management applications or treatments.
How are grazing records used? Grazing records are a collection of information which should include pasture identification, grazeable acres in each pasture, number of days grazed during each grazing event, number of head or animal units grazing, average weight per head or animal unit, recovery period, fertility or financial inputs, rainfall, and residual forage height. Such information is summarized and then used to make various assessments.
In the example below, data from a simple four-pasture grazing system has been summarized. The forage base is bermudagrass, totaling 120 grazeable acres. All pastures are fertilized. The cow herd consists of 40 head averaging 1,100 pounds. Two bulls weighing 1,500 pounds run with the cows during the 90-day breeding season. Table 1. summarizes the grazing day data for each pasture.
In order to transform the grazing days into estimates of production, one must standardize the units. In this example, an animal unit (AU) is the unit used. One AU equals 26 pounds of dry matter (DM) which is the average amount of DM a 1000-pound cow will consume per day. An 1100-pound cow then becomes 1.1 AU's and a 1500-pound bull becomes 1.5 AU's. Therefore the 40 cows represent 44 AU's and the two bulls equal 3 AU's. When we combine the information from Table 1 with our AU information, we create estimates of production, as shown below in Table 2.
Table 2 takes the total grazing AU days (AUD) for each pasture and converts it to a per acre basis, which is the baseline information we need to compare production between pastures. Table 2 compares production in terms of AUD per acre, grazed DM per acre, and estimated total production. In order to estimate total production, we assume a harvest efficiency of 50% in this example. Harvest efficiency increases as the number of pastures in the grazing rotation increases, assuming stocking rate is near carrying capacity.
Once the production parameters are produced, we can compare the pastures' responses to fertilization. In Table 3, the grazed DM per acre production estimates are used to assess production relative to nitrogen (N) inputs. Table 3 demonstrates the N response if pastures 1 and 3 are fertilized at 200 lbs. of 34-0-0 (nitrate) and pastures 2 and 4 are fertilized at a 300-pound nitrate rate. Rankings are based on production relative to an acre and to fertility rate. Note the ranking differences below between the production per acre and the production per N applied.
Production estimates such as these collected over a period of years become useful information for making management decisions. We as producers should always put a greater proportion of our investments into the areas that have the greatest return. This applies in forage and grazing management also. Those pastures identified as the more productive ones should receive disproportionately more inputs because they will return more to us over time.
Low production areas may never contribute acceptable returns, and should be the last areas to be considered for input. Without grazing records, meaningful production estimates are difficult to attain for proper assessment of a grazing or forage system. There are numerous grazing record forms developed by different entities, but a simple notebook works well and can be tailored to fit an individual's needs. The important point to be emphasized is grazing records are valuable information when recorded consistently, summarized and analyzed on a regular basis. Contact a forage specialist for more information.
As a final note, Table 4 illustrates the conversion of hay production into terms relative to the grazing production. In this example, the hayfield is 20 acres of bermudagrass, fertilized with nitrate (34-0-0) at 500 pounds per acre (170 units of N) in two applications. There are 98 bales produced weighing an average of 1200 pounds each. Note the conversion to the different units.