Grazing Arithmetic Dennis Hancock Extension Forage Specialist UGA – Dept. of Crop and Soil Sciences Dennis Hancock Extension Forage Specialist UGA – Dept. of Crop and Soil Sciences 2009 Georgia Grazing School

Grazing Pressure Productivity Per Animal vs. Per Acre Product animal Product animal Undergrazing Overgrazing

Grazing Pressure Undergrazing Overgrazing Productivity Per Animal vs. Per Acre Product animal Product animal Product acre Product acre Optimum

Stocking Rate vs. Density Stocking Rate Animals per acre over all acres and a period of time  (e.g., months, a season, a year) 675 acres 338 cows 2 acres 1 cow

Stocking Rate vs. Density 338 cows 22.5 acres 1 acre 15 cows Stocking Density Animals per acre at any one point in time  (e.g., within a given paddock)

Basic Grazing Numbers Animal Data  Animal Weight (lbs)  Rate of Dry Matter Intake (DMI, %)  Head Grazing Data  Rest Period (d)  Days in a Given Paddock (d)  Number of Paddocks  Grazing Efficiency (%)  Paddock Size (acres) Production Data  Acres Available (acres)  Available Forage before (lbs/acre)  Available Forage after  Available Forage diff  Stocking Rate  Stocking Density Available Forage Need Logistics

Basic Grazing Numbers Animal Data  Animal Weight (lbs)  Rate of Dry Matter Intake (DMI, %)  Head Grazing Data  Rest Period (d)  Days in a Given Paddock (d)  Number of Paddocks  Grazing Efficiency (%)  Paddock Size (acres) Production Data  Acres Available (acres)  Available Forage before (lbs/acre)  Available Forage after  Available Forage diff  Stocking Rate  Stocking Density Available Forage Need Logistics

Estimating Forage Need By % of body weight (Table Data): Animal ClassForage Intake Range (DM as a % of b.w.) Dairy cow Dairy heifer Bull Beef, cow (dry) Beef, cow (late gest.) Beef, cow (early lact.) Beef, stocker (steer) Beef, stocker (heifer) Beef, finishing Beef, replacement heifers Sheep, ewes (dry) Sheep, ewes (late gest.) Sheep, ewes (early lact.) Horse, Mature (maint.) Horse, Mature (late gest.) Horse, Mature (early lact.) Horse, Weanling (< 600 lbs) Horse, Yearling ( lbs) Goat, nanny (dry) Goat, nanny (late gest.) Goat, nanny (early lact.)

Estimating Forage Need By % of body weight (Table Data): Animal ClassForage Intake Range (DM as a % of b.w.) Dairy cow Dairy heifer Bull Beef, cow (dry) Beef, cow (late gest.) Beef, cow (early lact.) Beef, stocker (steer) Beef, stocker (heifer) Beef, finishing Beef, replacement heifers Sheep, ewes (dry) Sheep, ewes (late gest.) Sheep, ewes (early lact.) Horse, Mature (maint.) Horse, Mature (late gest.) Horse, Mature (early lact.) Horse, Weanling (< 600 lbs) Horse, Yearling ( lbs) Goat, nanny (dry) Goat, nanny (late gest.) Goat, nanny (early lact.) Beef, cow (dry) Animal ClassForage Intake Range (DM as a % of b.w.)

Estimating Forage Need By % of body weight (Table Data): Beef, cow (dry) Animal ClassForage Intake Range (DM as a % of b.w.) 2400 lbs/d=1200 lb cow 2.0%/hd/d 100 hdxx Daily Forage Need - Calculator

Basic Grazing Numbers Animal Data  Animal Weight (lbs)  Rate of Dry Matter Intake (DMI, %)  Head Grazing Data  Rest Period (d)  Days in a Given Paddock (d)  Number of Paddocks  Grazing Efficiency (%)  Paddock Size (acres) Production Data  Acres Available (acres)  Available Forage before (lbs/acre)  Available Forage after  Available Forage diff  Stocking Rate  Stocking Density Available Forage Need Logistics

Rest Period and Occupancy depend on the Growth Curve Available Forage (dry mass/unit area)

Grazing Rules of Thumb Crop Target Height (inches) Recommended Rest Period (days) Begin GrazingEnd Grazing* Alfalfa (grazing types) Annual Ryegrass Bahiagrass Bermudagrass Clover, White Clovers, Other Orchardgrass Pearl millet Small grains Sorghum/sudan Switchgrass Tall Fescue * Height at end of grazing should take into consideration lower quality forage.

Paddock Number How many paddocks should I use? Ideally, one should first consider the needs of the grass.  How much rest period is needed?  How long should I keep them in a paddock?  i.e., how many days between rotations? Number of Paddocks = Days of Rest Days of Grazing Paddocks = days of rest 3 days of grazing

Paddock Size How big should my paddocks be? This is where it all comes together…  But, there’s one element we still need to measure.  We’ll come back to that!  In the meantime, let’s refresh our memory on grazing efficiency. Paddock Size Animal Weight x %DMI x Head x Days in Paddock Available Forage diff x Grazing Efficiency % =

Mechanical Hay30-70% Silage60-85% Green Chop70-95% Efficiencies of Grazing and Mechanized Harvest MethodEfficiency Grazing Continuous Stocking30-40% Slow Rotation (3-4 paddocks)50-60% Moderate Rotation (6-8 paddocks)60-70% Well-managed MiG70-80%

Basic Grazing Numbers Animal Data  Animal Weight (lbs)  Rate of Dry Matter Intake (DMI, %)  Head Grazing Data  Rest Period (d)  Days in a Given Paddock (d)  Number of Paddocks  Grazing Efficiency (%)  Paddock Size (acres) Production Data  Acres Available (acres)  Available Forage before (lbs/acre)  Available Forage after  Available Forage diff  Stocking Rate  Stocking Density Available Forage Need Logistics

The Primary Calculations Paddock Size Animal Weight x %DMI x Head x Days in Paddock Available Forage diff x Grazing Efficiency % = = Days of Rest Days in Paddock + 1 Number of Paddocks Available Acres = x Paddock Size Number of Paddocks Grazier's Arithmetic: A Grazing Calculator

Tracking Forage Availability Rising plate meter  (falling plate) Rising plate meter  (falling plate)

Tracking Forage Availability

Tracking Forage Availability Grazing Stick STAND RATING ForageThinGoodThick --- (dry lbs/acre/inch) --- Bermudagrass Fescue Fes. + Clover Ryegrass Small grain

Grazing “Wedge” – May 15

Grazing “Wedge” – Dec. 1 Grazing Wedge Calculator

Resources

Grass Productivity – Andre Voisin, On Google Books or available for purchase

Questions?