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Grazing Systems for Beef Production: What are the Benefits?

Justin Derner

Justin.Derner@ars.usda.govrrru.ars.usda.gov

Cheyenne, WY

Road Map

Fundamental questions Evidence-based

assessments Long-term experiment

Literature review Role of Grazing

Systems Conclusions Questions/Discussion

Definition

Grazing system: Movement of livestock between two or more subunits of rangeland such that alternating periods of grazing and no grazing (rest) occur within a single growing season (Heitschmidt and Taylor 1991)

Intensive short duration grazing systems implemented by managers and studied by researchers since 1980 (Briske et al. 2008)

Why Implement Grazing System?

Enhanced plant and animal production Increased intensity of management Increased flexibility of operation Facilitate animal management and

veterinary care Personal goals and values Adaptive management applications Attainment of specific outcomes

Fundamental Questions

Managers have found that rotational grazing systems can work for diverse management purposes….but, scientific experiments have demonstrated that they do not necessarily work for specific ecological purposes.

Contradictory…, but can be reconciled by giving equal importance to biophysical variables and to human variables (goal setting, experiential knowledge and decision-making)

Fundamental Questions

Scientific evidence refuting ecologicalbenefits of rotational grazing is robust, but narrowly-focused (intentionally excluded human variables)

Grazing management and grazing systems are two different issues – separation of the human dimensions and the implementation of practice/infrastructureaspects

RESULTS FROM A LONG-TERM GRAZING EXPERIMENT

NORTHERN MIXED-GRASS PRAIRIE

High Plains Grasslands Research Station

15 inch average precipitation

Mixed-grass prairie 1380 pounds/acre

average forage production

Elevation from 6200-6400 feet

128 day growing season

Treatments

Stocking Rates Moderate 7.5 acres/steer

Heavy 5.5 acres/steer

Grazing Systems Season-long June-mid October

Short-duration 8 paddocks 4 cycles of 2, 3, 5 and 7 days

Response Variables

Yearling beef cattle weight gains Weighed prior to and following grazing season

Vegetation production Harvested in late July/early August from temporary exclosures

Study Notes

Started in 1982, results through 2006 reported Longest known grazing system X stocking rate study in North America

No grazing in 2000 and 2002 Severe droughts

Grazing seasons shortened in 1994 and 2006

Livestock Weight Gains

Stocking RateModerate Heavy Season-long Short-durationAv

erag

e D

aily

Gai

n (p

ound

s/he

ad/d

ay)

1.5

1.6

1.7

1.8

1.9

2.0

2.1

2.2 1991-2006 Dry Average Wet

Grazing System

*

* * ** *

Derner et al. 2008

Vegetation Production

Stocking RateModerate Heavy Season-long Short-durationVe

geta

tion

Prod

uctio

n (p

ound

s/ac

re)

500

1000

1500

2000

25001991-2006 Dry Average Wet

Grazing System

Derner and Hart 2007

LITERATURE REVIEW

USDA-NATURAL RESOURCE CONSERVATION SERVICE (NRCS),

CONSERVATION EFFECTS ASSESSMENT PROJECT (CEAP)

Plant and Animal Responses

Briske, Derner, Milchunas, Tate – CEAP Prescribed Grazing Chapter, in press

Plant and Animal Production

Briske et al. 2008

Vegetation Composition

Briske, Derner, Milchunas, Tate – CEAP Prescribed Grazing Chapter, in press

Vegetation Composition

Briske, Derner, Milchunas, Tate – CEAP Prescribed Grazing Chapter, in pres

Forage Responses

Forage quality: Inconsistent responses to grazing system

short, periodic non-grazing periods do not always coincide with favorable growth conditions

Livestock selectivity Grazing system does not override livestock preference for site selectivity Rainfall variability and associated lack of

predictability of plant growth appear to override the potential benefit derived from the redistribution of grazing pressure in space and time

Tiller Defoliations

Rotational grazing may not control the frequency and intensity of plant defoliation as effectively as often assumed

Difficult to obtain high percentage of tiller defoliations (>80%) before multiple defoliations occur within a single grazing period (Jensen et al. 1990)

Soil Hydrologic Function

Grazing system has similar or improved soil hydrologic function at moderate stocking rates

Soil hydrologic functions degraded by heavy stocking generally cannot be overcome by grazing system alone

Soil hydrologic function can recover with prolonged (>1 yr) rest

Wildlife

Grazing system generally has neutral effects on grassland birds Longer rests often beneficial to increase structural aspects of vegetation

Deer generally are negatively affected by grazing systems

Elk not affected by grazing system, but are sensitive to stocking rate

Generally, many false claims and few valid studies in the literature

General Conclusions from Experimental Evidence

Grazing system does not promote primary or secondary production compared to continuous grazing Consistent with previous reviews

Sampson 1951, Heady 1961, Van Poolen and Lacey 1979, O’Reagain and Turner 1992

Stocking rate and weather variation account for much of the variability associated with plant and animal production

WHAT IS THE ROLE OF GRAZING SYSTEMS?

WHY DO PRODUCERS USE THEM?

Role of Grazing Systems

Experimentally it is extremely difficult to mimic livestock movements and defoliation patterns used by managers

Grazing systems research has carefully evaluated ecological responses, with vast majority of results indicating no clear advantage of any one grazing system over another in terms of ecological benefits

Role of Grazing Systems

Contributions of grazing systems to broad conservation goals and ecosystem services have yet to be evaluated

Not only sufficient to evaluate whether or not grazing system is effective, but why is it effective? Place emphasis on facilitating practices or adaptive management skills?

Role of Grazing Systems

Importance of effective adaptive management is widely acknowledged but poorly studied Management goals, abilities and opportunities, personal goals and values (human dimensions aspects)

Research and monitoring on ranch scale operations is needed e.g., Pinchak et al. 2010, Ansley et al. 2010, Teague et al. 2010

Grazing System X Management

What does a grazing system do for grazing management? Facilitates forage inventory, animal care, and monitoring?

Facilitates greater managerial control and responsiveness?

Management skills vs. rules of thumb? Can grazing systems be helpful to

management if they do not increase production?

Questions?

Justin.Derner@ars.usda.govwww.rrru.ars.gov