RS300
Sample UnitExam
10-11-99
Given: A rangeland area in NE Wyoming, a mixed grass prairie in an area of about 15 inches of precipitation, produces a peak standing crop of desirable plants for sheep of about 1000 lb per acre. The area is 10,000 acres. The setting is early spring and early summer. Each ewe has 1.4 offspring. Ingestion or consumption per day (per ewe-lamb pair) was estimated from the formula [I call this the Rittenhouse quick and dirty method]: [(Fecal output x physiological demand compared to maintenance) divided by the indigestion coefficient; or, {(150 lb x .0143) x (1.3)}/(1-.60) = 6.97 or 7 lbs forage intake/day.
1. The 0.6 in the formula represents: (a) digestion? (b) digestibility? (c) the digestion coefficient?
2. Use the 7 pound/day number. What is the AUE of a ewe-lamb pair? AUE = .267
3. So, this area produces about 10, 000, 000 lbs of palatable, desirable forage. The actual production is (a) lesser than this number. (b) greater than this
number
4. Assume a harvest efficiency of .35. Animals are here only 60 days. What is the approximate forage supply, expressed as total AUMs?
[(1000 lb/acre)*(10000 Acres)*(.35)] ÷ 780 = 4487 AUM
5. How many AU (ewe-lamb pairs) could graze this area for the 60 days?
[Note this handy formula: AUM = (AU)(AUE)(M)]
4487 = (AU)*(.269)*(2)
AU = 8340
6. What is estimated carrying capacity, expressed as acres/AUM?
10000 acres/4487 AUM = 2.23 acres/AUM
7. Carrying capacity and stocking rate have the same units. (a) true (b) false
8. How many acres were allotted per sheep (AU)? 1.2 acres per AU
9. Write in your own words what an AUM of forage demand represents:
780 pounds of forage, dry matter basis
10. Write in your own words what an AUM of forage supply represents:
780 pounds of edible forage, dry matter basis
11. What are the 3 criteria we used to distinguish among range sites?
1. Kind of plants
2. Composition of plants
3. Production
12. Another important attribute of the range site is vegetation response to treatment. We assume similar response to some control variable, like grazing intensity,
across all locations.(a) true (b) true
13. The wife and I went to Denver yesterday to pick up a Turkish delegation at DIA, but decided to kill some time and did the IMAX Amazon and wandered in
the museum. I remember seeing a placard stating a 6 ton elephant eats about 300 lb of forage a day. What is the average Animal Unit Equivalent (AUE)?
AUE = 11.5
14. The Forage Acre Factor has units of: Acres/AUM
Given:
| Range Site | Acres | Median year production | Distance from water factor | Slope factor | Forage palatable to target animal | Harvest Efficiency | Potentially consumed forage |
Forage Acre Factor | AU per site, 4 month season, AUE = 1 |
| Loamy Plains | 2463 | 950 | 1.0 | 1.0 | .85 | .3 | 596661 | 3.22 | 191 |
| Loamy Plains | 432 | 1050 | .5 | 1.0 | .85 | .3 | 57834 | 5.80 | 18 |
| Shaly Plains | 564 | 840 | .5 | .85 | .85 | .3 | 51343 | 8.50 | 16 |
| Overflow | 247 | 1450 | 1.0 | 1.0 | .90 | .25 | 51343 | 2.40 | 26 |
| Sandy Plains | 1640 | 1250 | 1.0 | 1.0 | .90 | .3 | 553500 | 2.31 | 177 |
|
Total =
|
428 |
How many animals for the season? 428 AU
What was average stocking rate, AUM per acre? .3 = 1719/5346
What was average stocking rate Acre per AUM? 2.97 = 5346/1719
RS300
In Class
10-13-99
Given: A 10,000 acre rangeland in the sandhills of Nebraska. 2000 Acres is grazed by 265 yearling steers (AUE = .75) for about 4 months, 7000 acres is grazed by 275 cows and calves (AUE = 1.45) for 5 months and 275 cows alone (AUE = 1) for 2 months, 1000 acres is hayed and produces 1.5 tons per acre. One ton of hay is equivalent to 2.5 AUMs.
What is the average stocking rate on the 9,000 acre, expressed as AUM/Acre? The key formula is AUM = (AU)(AUE)(T)
265 *.75*4 = 795 AUM
275*1.45*5 = 1993 AUM
275*1.0*2 = 550 AUM
Total = 3338
How many AUMs of forage does this ranch produce in one year.
1000*1.5*2.5 = 3750 AUM from hay
Total = 3750 AUM + 3338 AUM = 7088
Given: A stocking rate of .20 AUM/Acre; a grazing season of 5.0 months; the area is 40000 acres.
What is the stocking rate expressed as Acre/AUM?
1/.20 = 5
How many cows and calves (AUE = 1.2) could be grazed on the area? Key formula is: [(AU)(AUE)(T)] ÷ ACRES = AUM/ACRE
.2 = [(AU)(1.2)(5)]/40000 = 1333
How long could the same number of 1300 lb cows and their calves be grazed on the same area (AUE = 1.66)? Key formula is: [(AU)(AUE)(T)] ÷ ACRES = AUM/ACRE
.2 = [1333AU)(1.66)(M)]/40000 = 3.6
If all the cows and calves were removed, how many steers (AUE = .70) could be grazed on this area for the same 4 mo season? Key formula is: [(AU)(AUE)(T)] ÷ ACRES = AUM/ACRE
.2 = [(AU)(.70)(4)]/40000 = 2857
Given: A rangeland is 9,000 acres in size. The stocking rate is 24 acres/AUY (AUE = 1.0). The area is grazed for 180 days.
How many animals graze the area? Note: this scenario has lots of apples and oranges; i.e., years/days/months. Key formula is: ACRES ÷ [(AU)(AUE)(T)] = ACRES/AUY
24 = 9000/[(AU)(1.0)(180/365)] = 760, or
2 = 9000/(AU)(1.0)(6) = 750
Difference is assumption about portion of year vs average days in a month
Given: An elk was found to consume about 400 lb dry matter/mo.
400/780 = .51
Given: A herd of 92 elk, including 42 females (620 lb), 18 adult males (850), 12 yearling males (340 lb), and 20 yearling females (320 lb).
What is an estimated demand of this herd for 1 month, pounds? Answer has to be in pounds. First key idea is AUE is a unitless ratio, i.e., units in numerator must be the same as units in the denominator. Second key is that a standard demand unit is 26 lb dry matter per day. Calculate demand of each age class and add ’em up.
42*.62*26*30 = 20311
18*.85*26*30 = 11934
12*.34*26*30 = 3182
20*.32*26*30 = 4992
Total demand per month is 40419 lbs