Grazing Management Principles for Rangelands

Mort Kothmann Texas A&M University

Four Basic Principles of Grazing Management

► Stocking rate ► Season of grazing ► Distribution of grazing across landscape ► Match kinds and classes with the rangeland vegetation, topography and climate

Grazing Management Concepts

Basic tenets of grazing management ► Grazing intensity (degree of use)  Light – moderate – heavy – extreme ► Methods for monitoring degree of use  Key area method (Key species)

Grazing Intensity

► A certain amount of plant biomass must remain to maintain to assure health of animals, plants and soil   Herbivore diet Plant vigor and reproduction  Soil stability

Grazing Intensity

► As annual precipitation declines, sustainable level of forage utilization generally decreases  Sustainable intensity of grazing is directly related to availability of water and soil nutrients  Greater resource availability increases proportional allocation to shoot relative to root

Grazing Intensity

► Recommended levels of use based on field estimates and (harvest efficiencies)     Ryegrass (water & N unlimited) 75% Coastal Bermudagrass pasture 50% (70-80%) (40-60%) Humid tall grassland 40-50% Semiarid grasslands: 20-30% (20-30%) (15-20%)  Arid SW & Intermountain West: 15-20% (10-15%) The more arid the land, the lower the sustainable intensity of use.

Monitoring Range Utilization

► Key Species Method for monitoring use  Monitor utilization of 1-3 key species that are abundant, productive, and palatable (decreasers or increasers) rather than monitor many species  Assumption: use of entire range is optimal when use of key species is optimal: ► Key species are moderately used – 30-40 % ► Secondary species are lightly used – 10-25 % ► “Ice-cream” plants may be overused – >40 %

Monitoring Range Utilization

► Key Area method for monitoring range use   Monitor an area that is “representative” of overall range condition, trend, and degree of seasonal use No rangeland is uniformly used – some “sacrifice” areas will occur due to area selectivity ► Heavy use – Clipped or mowed appearance  ► Moderate Use  >50 % of fair or poor forage plants used 50 % of good or fair forage plants used ► Light use  Only choice plants used

Monitoring Range Utilization

► Key Area method for monitoring range use  Optimal stubble height in key areas following grazing vary: ► Tall-grasses  30-35 cm (12-14 inches) ► Mid-grasses  15-20 cm (6-8 inches) ► Short-grasses  5-8 cm (2-3 inches)

TGM for Monitoring Degree of Use

► Using the Demand Day (DD) as a measure of animal production and maintenance from the pasture.

  Energy required for maintenance and growth is estimated from animal weights and expressed as DD.

Productivity of the pastures is estimated from observed animal production and degree of use on the pasture.

Season of Use

► Yearlong  Used primarily in tropical & sub-tropical climates ► Seasonal  Temperate to cold climates  Tame pastures ► Rotational  Grazing Systems (This will be covered in a separate presentation.)

Length of Grazing Season vs Growing Season

► Rangelands– Grazing season is generally longer than the growing season. This requires stockpiling forage for use during the non-growing season. This frequently involves very light use during the peak growing season.

► Tame Pasture– Grazing season is matched with the growing season to harvest forage near maximum quality. Stockpiling forage usually involves shortening the grazing period during active growth.

Timing of Grazing

► Effect of grazing varies according to:   Season of use -- Plants are more resistant to intense herbivory during dormancy than in active growth.

Phenological stage of plant -- Defoliation in spring when plants start growth may be less harmful than in fall when plants are flowering and maturing.

 Opportunity for regrowth – Will plants be able to produce new leaves and develop strong root systems prior to entering dormancy following defoliation?

Grazing Distribution: Animal Selectivity

► Area distribution    Landscape Patch Feeding station ► Species selective grazing ► Plant part selective grazing   Live or dead Leaf of stem

Area Selection

► Factors affecting area selection include:         Distance from Water Vegetation Type Topography (Slope) Range Site (Soils) Weather Animal pests such as flies Kind & class of animal Management practices such as supplementation

Distance from Water

► Recommended distances between watering points vary according to terrain, species of animal, and breed of livestock ► General recommendations:     Rough country: ≈ 0.5-mile max Rolling country: 1.0-mile max Flat sandy country: ≈ 1.5-mile max Flat country ≈ 2.0-mile max

Vegetation Type

► Herbivores select areas with vegetation that best meets their nutritional needs   Bulk grazers prefer open grasslands ► Cattle, Buffalo, White rhinos Browsers prefer wooded areas ► Mule deer, Giraffes, Black rhinos

Topography

Figure 10.2 Relationship of slope gradient to the percentage of observations of cattle, feral horses, deer, and bighorn sheep. (From Ganskopp and Vavra 1987. Reprinted with permission.) 70 60 50 40 30 20 10 Cattle Horses Deer Bighorn 10 20 30 40 50 Percent Slope 60 70 80+

Improving Livestock Distribution

► Provide supplemental feeds/mineral licks  Cattle move from water to grazing to salt: ► Change location of salt-mineral licks ► Place salt away from water in areas that grazing animals are avoiding ► Grazing systems that reduce pasture size and significantly increase animal density may improve livestock grazing distribution.

Improving Livestock Distribution

► Prescribed burning  Removal of previous years’ growth ► Greater access to new plant growth  Early spring fires can ► Increase soil temperature ► Initiate growth ► Improve forage quality ► Encourage earlier grazing

Improving Livestock Distribution

► Adjust kind/class of livestock  Changing animal species can improve livestock distribution depending on: ► Vegetation composition ► Water distribution ► Topography  Because of non-uniform plant composition, multi species animal production systems can increase: ► Herbivore distribution ► Vegetation use ► Animal production

Improving Livestock Distribution

► Fencing can be used to control:    Area selective grazing Season of use Rotational grazing systems  Use of high-value forages such as hay crops  Movement of wildlife

Livestock Distribution

► Negative Aspects of Fencing   Cost prohibitive where productivity is low Electric fences are less costly to construct than standard barbed wire but more expensive to maintain   Restrict movement of some wild species High-fencing to control game species

Kind & Class of Animal

► Kind of animal (species)  Cattle, sheep, goat, horse, wildlife species ► Class of animal (age, sex, physiological status)  Reproductive -- pregnant or open   Age -- mature or young Lactating or dry ► Adaptation to climate and forage quality  Breed of animal  Genetic potential for growth and lactation

Choice of Kind & Class of Animals

► Match animal genetics with forage quality ► Match the grazer with the landscape and the kinds of vegetation