Estimating Forage Need. Estimating Forage Need. Basic Grazing Numbers. Dr. Dennis Hancock Extension Forage Specialist Univ.

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1 Stocking Rate vs. Density Pasture-Based Dairy Summit Aiken, SC Paddock Sizing and Design Considerations Stocking Rate! Animals per acre over all acres and a period of time (e.g., months, a season, a year) 600 cows 300 acres Dennis Hancock Extension Specialist UGA Dept. of Crop and Soil Sciences 2 cows 1 acre Stocking Rate vs. Density Stocking Density! Animals per acre at any one point in time (e.g., within a given paddock) Animal Weight (lbs) Rate of Dry Matter Intake (DMI, %) Head 300 cows 5 acres 60 cows 1 acre Animal Weight (lbs) Rate of Dry Matter Intake (DMI, %) Head Rest Period (d) Days in a Given Paddock (d) Number of Paddocks Grazing Efficiency (%) Paddock Size (acres) Acres (acres) before (lbs/acre) after diff Stocking Rate Stocking Density Extension Specialist Rest Period (d) Days in a Given Paddock (d) Number of Paddocks Grazing Efficiency (%) Paddock Size (acres) Acres (acres) before (lbs/acre) after diff Stocking Rate Stocking Density Estimating By % of body weight (Table Data): Animal Class Intake Range 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.) (DM as a % of b.w.)

2 Estimating By % of body weight (Table Data): Animal Class 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 By % of body weight (Table Data): Animal Class Intake Range (DM as a % of b.w.) Dairy cow ,480 lbs/d 1200 lb cow x 3.4%/hd/d x 600 hd Daily - Calculator Efficiencies of Grazing and Mechanized Harvest Method Efficiency Grazing Continuous Stocking 30-40% Slow Rotation (3-4 paddocks) 50-60% Moderate Rotation (6-8 paddocks) 60-70% Well-managed MiG 70-80% Mechanical Hay 30-70% Silage 60-85% Green Chop 70-95% Animal Weight (lbs) Rate of Dry Matter Intake (DMI, %) Head Rest Period (d) Days in a Given Paddock (d) Number of Paddocks Grazing Efficiency (%) Paddock Size (acres) Acres (acres) before (lbs/acre) after diff Stocking Rate Stocking Density Rest Period and Occupancy depend on the Growth Curve Crop Grazing Rules of Thumb Target Height (inches) Begin Grazing End Grazing* Recommended Rest Period (days) (dry mass/unit area) 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 may need to be higher to optimize intake of quality forage or vigorous re-growth. Extension Specialist

3 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 Grazing Paddocks 24 days of rest days of grazing Paddock Size How big should my paddocks be?! This is where it all comes together These are assumptions over the LONG term. (year-long; mature system) Paddock Size 9.3 acres This can be reduced by assumptions of supp. rate [e.g., 9.3 (9.3 x 40%) 5.6] Animal Weight x %DMI x Head x Days in Paddock diff x Grazing Efficiency % 1200 lbs x x 600 x x 0.75 This assumes all DMI from pasture! Animal Weight (lbs) Rate of Dry Matter Intake (DMI, %) Head Rest Period (d) Days in a Given Paddock (d) Number of Paddocks Grazing Efficiency (%) Paddock Size (acres) Acres (acres) before (lbs/acre) after diff Stocking Rate Stocking Density Acres Paddock Size The Primary Calculations Paddock x Size Number of Paddocks Animal Weight x %DMI x Head x Days in Paddock diff x Grazing Efficiency % Analyzing Strategic Changes Acres ( ) d in Paddock +1 x Animal Weight x %DMI x Hd x d in Paddock diff x Grazing Efficiency %! Examples: Changes in grazing system, forage rest period, etc. Changes in supplementation rate! But, remember that the system is very dynamic! Number of Paddocks Days in Paddock +1 Grazier's Arithmetic: A Grazing Calculator Extension Specialist

4 Factors Affecting Substitution Rate! A lb of supplement or TMR does not a lb of pasture Generally, the range is a decrease of lbs of pasture per lb of supplement fed. Data on TMR substitution rates are sparse (highly variable)! High forage allowance (i.e., the cow has the ability to selectively graze) Higher quality pasture intake Low substitution effect of supplement Analyzing Substitution Effects Acres ( ) d in Paddock +1 x Animal Weight x %DMI x Hd x d in Paddock diff x Grazing Efficiency % diff Expected Grazing Efficiency 85% 80% 75% 70% Base stocking rate Sub rate Stocking rate coefficient * * Calculated inc. in stocking rate on a. ryegrass for ea. add. lb of supp. Assumptions Some advice and tricks! Start with an inventory. Acreage, soil type, fertility! Sketch out the ideal.! Use training wheels where possible. Temporary: Learning/Laborious Permanent: Convenient/Fixed! Build in flexibility. Pasture subdivision is just Step 1 Rational grazing is not just about subdividing a pasture into smaller sections. Rules of Thumb: Providing Water! Place water within ft of all parts of paddock. This will decrease herd behavior and the camping effect.! Isolate water, shade, feeders, and gates from one another. This will also dec. herd behavior and the camping effect. Place shade away from paddock entrance. Extension Specialist

5 Providing Water Providing Water Dairy cattle in direct sunlight may require 18% more free water than cattle under shade (Muller et al., 1994). Heat stress and cattle performance! Radiant energy (sunlight) increases surface and air temperatures.! Cattle in the sun vs. shade in hot environments had: higher internal body temperature (MitlÖhner et al., 2001) increased respiration (MitlÖhner et al., 2002) increased heart rate (Brosh et al., 1998) lower DMI, ADG and meat quality (MitlÖhner et al., 2002) decreased conception rates (Roman-Ponce et al., 1976) Extension Specialist

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