Lesson 1. Planning a Grazing System — Appendix D

Visual Method to Estimate Stand Productivity

Determine the average vertical height of the undisturbed stand of forage species in inches and use the table below to estimate the forage available for consumption.

Estimated dry matter yield in pounds per acre per inch of height for pasture types and stand conditions

Pasture Species Stand Condition, (lb./acre/inch)*
Fair Good Excellent
Bluegrass/Clover 150-200 250-300 350-400
Perennial Ryegrass/Clover 150-200 250-300 350-400
Orchardgrass/Legume 150-200 250-300 300-350
Timothy/Legume 150-200 250-300 300-350
Tall Fescue + Nitrogen 100-150 200-250 350-400
Mixed Pasture 150-200 250-300 300-350

*Values from Pasture Stick developed by Cornell University and NRCS

Tall growing species should be grazed at different heights than low growing species. Grazing should start in a paddock when vegetation is 6 to 8 inches high for tall growing species such as timothy, orchardgrass, bromegrass, and reed canarygrass and 4 to 6 inches high for low growing species like bluegrass, redtop, fine leafed fescues, sweet vernal, and white clover. For rapid regrowth and to maintain a healthy stand, animals should be removed when the forage height is reduced to 2-3 inches for tall growing species and 1 to 2 inches for low growing species.

For example, an Orchardgrass/legume pasture in excellent condition with an average undisturbed height of 7 inches will have 4 inches of usable forage (3-inch stubble height left after grazing). The available forage dry matter would be estimated to be 300-350 pounds/acre-inch or 1,200-1,400 pounds/acre.

Use the following formulas to calculate the number of animals that can be grazed or the approximate number of days the pasture can support a specific group of animals:

Total lbs. Forage/Ac. x #Ac. x  % Grazing Efficiency
Days =
Avg. Animal Wt. x Intake Rate in % Body Wt. x Animal #

 

Total lbs. Forage/Ac. x #Ac. x % Grazing Efficiency
Animal Number =
Avg. Animal Wt. x Intake Rate in % Body Wt. x Days #

 

Pasture system Grazing Efficiency (total season)
Continuous 30%
4 pastures 35%
8 pastures 50%
12 pastures 65%
24 + pastures 75%

For example,

1,300 lbs. Forage/Ac. x 1 Ac. X .75 Grazing Efficiency
19.5 Animals =
=  19 animals fed
1,250 lbs. Animal wt. x 4% (ie. .04) of Body Wt. Intake x 1 Day