The Demand Day A Unit for Adaptive Stocking Rate Management Austin Sewell Agren Inc., Carroll, IA.
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Transcript of The Demand Day A Unit for Adaptive Stocking Rate Management Austin Sewell Agren Inc., Carroll, IA.
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The Demand DayThe Demand Day
A Unit for Adaptive Stocking Rate Management
Austin Sewell
Agren Inc., Carroll, IA
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Definition:
The Demand Day (DD) is a standard unit of measure of forage demand for large wild or domestic herbivores.
1 DD equals 12 Megacalories (Mcal) per day intake of net energy for maintenance and gain.
What is a Demand Day?
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Meets criteria for a standard unit of measure (Hinnant 1994)
1. The standard should be readily and widely accessible.
2. The standard should be easy to use.
3. The standard should be invariable.
Legitimacy
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Formula
12
0.454ADG60.454W0.077 0.750.75
NEm (Mcal) + NEg (Mcal)
12
Demand UnitEquivalent*
=
=
*Where NEm is net energy for maintenance, NEg is net energy for gain or loss, W is average animal bodyweight in pounds, and ADG is average daily gain or loss of animal bodyweight in pounds.
Demand Days = Demand unit equivalent multiplied by No. of days
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Example
1150 lb. cow with calf, 2 months old, gaining 1.1 lbs. per day
Average cow weight = 1150 lbs.
Calf born at 80 lbs, 160 lbs at 2 months, ADG = 1.1
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0.7
12
8.4
12
00.45411500.077 0.75
Cow demand equivalent:
12
0.454ADG60.454W0.077 0.750.75 =
=
Example (cont.)
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0.4
12
3.61.5
12
0.4541.160.4541200.077 0.750.75
Calf demand equivalent:
=
=
12
0.454ADG60.454W0.077 0.750.75
Example (cont.)
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Cow-calf pair demand equivalent:
0.7 + 0.4 = 1.1
Example (cont.)
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Example
Computer applications (TGM)
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Animal Unit
Ambiguous past
Should be defined as 26 lbs Dry Matter intake per day (Scarnecchia 1985)
Meets Hinnant’s criteria as a standard unit of measure
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DD vs. AUD
Similarities
Both model forage intake.
Both standard units of measure for forage demand.
Differences
DD directly tied to animal production, AUD not.
DD considers forage quantity AND quality, AUD only considers quantity. (IES an example).
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SR Mgmt Practice Demand Side Supply Side
Setting Initial SR Historical grazing records
Vegetation inventory (composition, biomass)
Monitoring SR Forage demand, use ratings
Vegetation monitoring
Adjusting SR Relies on actual forage demand and pasture use ratings
Relies on vegetation monitoring
Simulating forage balance
Nutrient supply Spp. composition, biomass production, harvest efficiency
Demand Side vs. Supply Side
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Class Subclass[1]
PDR[2] Range (%)
Representative PDR Value[3] (%)
Description
None 0-10 5Vegetation appears practically undisturbed when viewed from an angle or from a distance.
Light
− 10-16 13
Preferred areas and high-choice[4] forage show moderate use.
Light use of primary[5] or low-choice[6] forage.16-34 25
+ 34-40 37
Moderate
− 40-44 42 Most accessible forage shows use.
High-choice forage heavily used.
Primary forage is moderately grazed and supplying most of the demand.
Light use of low-choice forage.
46-56 50
+ 56-60 58
Heavy
− 60-66 63High-choice forage completely used.
Primary forage is closely grazed over most of the area.
Moderate use of low-choice forage.
66-84 75
+ 84-90 87
Severe 90-100 95
Pasture appears stripped of forage.
Primary forage almost completely used.
Low-choice forage shows considerable use and is carrying the grazing load.
Pasture Use
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Light Moderate Heavy
10-40 40-60 60-90
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Ind
. A
nim
al
Pro
du
cti
on
PDR (Cum. DD used/Cum. DD produced)
Pasture Use Rating (%PDR)
None Sev.
0-10 90-100
Curve based on Hart (1986)
Pasture Use
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System of Use
Re al World
M e asure me nts& Obse rv ations
Re cordKe e p ing &Plann ing
Pasture:Forage
Animals:K ind of animalC lass of animalPhy siologic al
status
Intake (ac tual)
Pas ture use rating(see guide)
Am ount of feeds (drym atter; w eight)
An ima l Numbers; Bodywe igh t; D a tes in & ou t
Observed PDR (DDused/DD produc tion)
Pasture Produc tion
Calc ulated ME intake
DD used from pasture
Dem and Day s
D iet Selec tion
Feeds
Forage BalanceS im ulation (T G M)
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Adaptive SR Management
Stocking rate needs to be managed more adaptively – more responsively and proactively
For this, we need quicker turnover of management phases.
Demand side methods have faster turnover
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Why the Demand Day?
Advantages over AUD
Accounts for forage quality
Directly related to animal production
Better suited for demand side approach to stocking rate management
Better suited to Productivity-Stocking Rate theoretical model
Demand side better suited to forage balance simulation (Rittenhouse and Bailey 1996)
Demand side stocking rate management better suited to adaptive management
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References
Hart, R. H. 1986. How important are stocking rates in grazing management? In. P.E. Reece and J.T. Nichols (Eds.). Proceedings, The Ranch Management Symposium, November 5-7, 1986, North Platte, Nebraska. Univ. Neb. Ext. Serv., Lincoln, Neb., pp. 77-87.
Hinnant, R. T. 1994. What is an animal-unit? A time to conform. Rangelands: 16(1) pp 33-35.
Rittenhouse, L. R. and D. W. Bailey. 1996. Spatial and Temporal Distribution of Nutrients: Adaptive Significance to Free-Grazing Herbivores. Proc. Grazing Livestock Nutrition Conf. 3:31-61.