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RGSC_294_week 11&12 (2)

RGSC_294_week 11&12 (2) - Grazing management basics 1...

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1 1) Proper number of livestock Grazing management basics 2) Proper kind of livestock 3) Proper season of grazing 4) Proper distribution of animals 1. Proper number of livestock Stocking rate: Amount of land allocated to each animal unit for the grazable p i d f th period of the year. [ AU/area/time] Animal unit: A mature cow (1000 lb [455kg]) either dry or with a calf up to 6 months of age. This animal would be expected to consume: 20 lb (9.1 kg) 1 day 600lb (273 kg) 1 month 7,300 lb (3,318 kg) 1 year Stocking rate Carrying capacity
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2 Importance of Stocking rate Selection of the correct stocking rate is considered the most important of all grazing management decisions It affects: 1. Rangeland vegetation 2. Animal production 3. Economic returns 4. Wildlife habitat 5. Ecosystem functions Long term effects of stocking rates on rangelands Trend (changes in plant community composition) Productivity (changes in the flows of energy and matter)
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3 Stocking rate levels Heavy grazing: about 60% utilization Moderate grazing: about 40 % utilization Light (conservative) grazing: about 30% utilization Many studies have investigated the influence of stocking rates on: 1. Vegetation productivity (lb/acre/yr) 2. Vegetation trend (change in ecological condition) 3. Intake and nutritional quality of animal diets 4. Animal production (weight gains/head & weight gains/acre) 5. Financial returns
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4 1. Stocking rates and rangeland vegetation (productivity) Heavy Moderate Light Utilization (%) 57 43 32 Avg. forage production (lb/acre/yr) 1,175 1,473 1,597 Forage production 820 986 1,219 drought years (lb/acre) Summary of 25 studies evaluating the effects of grazing intensity on rangeland condition in North America (Holecheck et al. 1999) Grazing % % studies showing: 2. Stocking rates and rangeland vegetation (trend) Intensity Use = Heavy 51-65 90 10 0 Moderate 40-50 23 30 47 Light < 40% 5 21 74 Summary of 25 studies evaluating the effects of grazing intensity on rangeland condition in North America (Holecheck et al. 1999)
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5 3. Forage intake and nutritional quality in relation to stocking rate % Use Intake Kg/day Diet CP Diet Digest Pieper et al. 1959, Sheep, Utah Mod. 37 % 1.9 6.0 48 Heav. 75% 1.6 5.8 38 Vavra et al 1973 Light 4 4 11 3 57 Vavra et al. 1973, cattle, Colorado 20% 4.4 11.3 Heav. 60% 3.7 11.3 52 4. Stocking rates and individual animal production + Ind. Animal Weight Gain - - Stocking rate +
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6 4. Stocking rates and production per acre re + .Animal Weight Gain/acr - - Stocking rate + 4. Animal responses in relation to remaining herbaceous biomass Location: Short grass prairie - Colorado Grazing period: July 1 - October 31
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7 5. Financial returns and stocking rates Range Type Grazing Intensity % Util Net return Acre $ Chihuahuan desert, NM Cow-calf (Holechek 1991) Heav. Light 50-60 30-35 +0.32 +0.75 Shortgrass prairie , CO Yearlings ( Kipple & Costello, 1960) Heav.
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