Planning Procedures For Rotational Stocking Methods
Although there are a number of different ways in which to develop prescribed grazing management plans, the following procedures have been created to provide practical guidelines which can be applied to regulate forage quality, quantity, and harvest efficiencies at critical stages of the season, and without undue complexity of management or high cost.
Step 1. Estimate The Total Forage Requirement
The amount of forage dry matter required to sustain pasture health and productivity as well as achieve the desirable level of animal performance is called the total forage requirement or the forage demand. It is based on having enough forage available to meet the daily dry matter intake requirements of the herd or flock with an additional amount above that to ensure that overgrazing or other damage to the plant resource does not occur. This value is estimated by calculating the forage requirement per animal per day and then multiplying this value by the total number of animals.
The amount of forage dry matter required for each grazing animal i.e. its daily forage requirement is, among other factors, directly related to how much it weighs. As a general rule, livestock require an amount of dry matter per day equal to 2.5 to 3.0 percent of their body weight. Although a lactating dairy cow may require more than this, the remainder of the ration is generally provided in the barn and fed in response to a particular level of milk production.
To calculate the daily forage requirement for livestock other than lactating dairy cows multiply the weight of the animal by 2.5 percent (.025). For lactating dairy cows multiply the animal weight by 3.0 percent (.03). For planning purposes, it is better to err on the side of calculating too high of a forage demand and wasting some feed, rather than estimating too little and not meeting the livestock demand.
ANIMAL WEIGHT X .025 OR .03 = DAILY FORAGE REQUIREMENT/ ANIMAL
Table 2: EXAMPLES OF DAILY FORAGE REQUIREMENTS
Lactating dairy cow weighing 1300 lbs.
1300 X .03 = 39 lbs DM/day |
Beef cow/calf pair with a combined weight of 1400 lbs
at midsummer
1400 X .025 = 35 lbs DM/day |
Ewe/lamb pair with a combined weight of 200 lbs
at mid-summer
200 X .025 = 5 lbs DM/day |
Steer, Heifer, or other growing livestock weighing 650
lbs at mid-summer
650 X .025 = 16.25 lbs DM/day |
To determine the DAILY HERD/FLOCK FORAGE REQUIREMENT multiply the per animal daily forage requirement by the number of animals.
FORAGE REQUIREMENT/ANIMAL/DAY X NUMBER OF ANIMALS = DAILY HERD/FLOCK FORAGE REQUIREMENT
In planning to meet the forage requirement for growing animals such as cow/calf or ewe/lamb pairs, steers, heifers, etc., keep in mind that these animals start the grazing season at a much lighter weight than when they finish. Subsequently, the forage demand starts out low but increases over the grazing season as the livestock gain weight. To plan a system for these kinds of animals, use an average weight that would be expected midway through the grazing season. For cow/calf, ewe/lamb, or other livestock combinations, use the combined average weight of the pair at midseason.
Step 2. Estimate The Forage Supply
Determining the forage supply is the most difficult part of setting up a prescribed grazing management plan. This is because of the variability encountered in plant species composition and density, and the factors which control plant growth and yield. These factors include climatic conditions, soil type, soil fertility, and the level of management. As a result, actual measured yields obtained from the pasture will provide the most reliable estimate of the amount of forage available for grazing because they are directly related to the soil, plant, climatic, and management variables most closely associated with the site.
However, if there is no site specific information available, estimated potential grass-legume hay yields based on soil type may be substituted. This information is available in most county soil surveys which can be provided by either the Soil Conservation Service or Cooperative Extension Service.
Table 3 is a chart that estimates the amount of forage predicted to be available for grazing. It uses the grass-legume hay yield estimates reported in the Soil Conservation Service (SCS) Soils 5 database, expressed in Tons/Acre/Year, as a reference point or index to link the productivity of a particular pasture to it's soil type. However, because the yields indicated in the Soils 5 database tend to be lower than what most producers have experienced, data from actual on-farm observations are used to provide estimates of the amount of forage predicted to be available for grazing on a Pounds/Acre/Rotation basis.
TABLE 3: FORAGE AVAILABILITY ESTIMATES FOR USE WITH
ROTATIONAL STOCKING METHODS
Hay Yield
Tons/Acre/Year | 5.5 | 5.0 | 4.5 | 4.0 | 3.5 | 3.0 | 2.5 |
Forage Availability
Pounds/Acre/Rotation | 2200 | 2000 | 1800 | 1600 | 1400 | 1200 | 1000 |
Maximum spring rotation length 15 days.
Maximum summer rotation length 30 days. |
To use this table, first, locate the pasture on a soil survey map and determine the major soil type. Second, obtain the grass-legume hay yield from the Soils 5 database. Third, locate the hay yield estimate in the table and reference it to the corresponding forage availability factor.
Step 3. Determine The Paddock Residency Period
As previously indicated, lactating dairy cows have the greatest need for very short residency periods. In order to
maintain high and consistent levels of milk production, 1 day residency periods are recommended but can range between one-half and 2 days. Most all other classes and kinds of livestock can meet their nutritional requirements grazing
pastures with longer residency periods. However, where maximizing harvest efficiency is indicated, residency periods of 3 to 4 days are recommended.
Step 4. Calculate The Paddock Size
Once the forage demand, forage supply, and residency period have been determined for a particular livestock operation the size of individual paddocks can be estimated by dividing the forage demand by the forage supply and then multiplying this number by the residency period. The result will be the paddock size in acres.
(FORAGE DEMAND/ FORAGE SUPPLY) X RESIDENCY PERIOD = PADDOCK SIZE.
Step 5. Determine the Number of Paddocks Required
The number of paddocks required for a particular grazing plan is based on having enough available to provide an adequate regrowth interval during the slowest growth period of summer. As previously indicated, the combined experiences of many producers across New York State indicates that a 30 day maximum regrowth interval provides a reasonable compromise between maximizing forage quality and promoting maximum yield.
To calculate the number of paddocks required, divide the maximum regrowth interval (30 days) by the residency period selected and then add one additional paddock.
(30 / RESIDENCY PERIOD) + 1 = NUMBER OF PADDOCKS NEEDED
Step 6: Estimate The Number of Acres Required
Once the planning process has gotten this far along calculating the total number of acres required is fairly straight forward. Simply multiply the size of the paddock by the number of paddocks and you have it.
PADDOCK SIZE X NUMBER OF PADDOCKS = NUMBER OF ACRES PLANNED
See Appendix 1 for a prescribed grazing management plan worksheet to be used with rotational stocking methods.
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