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The Demand Day

The Demand Day. A Unit for Adaptive Stocking Rate Management Austin Sewell Agren Inc., Carroll, IA. What is a Demand Day?. Definition: The Demand Day (DD) is a standard unit of measure of forage demand for large wild or domestic herbivores.

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The Demand Day

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  1. The Demand Day A Unit for Adaptive Stocking Rate Management Austin Sewell Agren Inc., Carroll, IA

  2. What is a Demand Day? 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.

  3. Legitimacy Meets criteria for a standard unit of measure (Hinnant 1994) • The standard should be readily and widely accessible. • The standard should be easy to use. • The standard should be invariable.

  4. NEm (Mcal) + NEg (Mcal) 12 Formula Demand Unit Equivalent* = = *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

  5. 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

  6. Example (cont.) • Cow demand equivalent: = =

  7. Example (cont.) • Calf demand equivalent: = =

  8. Example (cont.) • Cow-calf pair demand equivalent: 0.7 + 0.4 = 1.1

  9. Example • Computer applications (TGM)

  10. 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

  11. 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).

  12. Demand Side vs. Supply Side

  13. Pasture Use

  14. PDR (Cum. DD used/Cum. DD produced) Pasture Use Rating (%PDR) 10-40 40-60 60-90 0-10 90-100 Light Moderate Heavy None Sev. Pasture Use Curve based on Hart (1986)

  15. System of Use

  16. 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 Adaptive SR Management

  17. 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

  18. 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.

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