Feed Value of Leafy Spurge
Sheep and goats can be effective tools to complement herbicides for control of leafy
spurge. In addition, their control efforts can generate an economic return from land that
other livestock won't graze. The land operator can control leafy spurge by grazing sheep
or goats and provide a highly nutritional diet for the livestock.
Leafy spurge is very nutritious and provides good forage for lambs, kids, lactating
ewes, and/or lactating nannies. The crude protein content of leafy spurge was found to be
greater than 27 percent in the early season, only declining to less than 20 percent after
maturity (Table 1).
Table 1. Nutritional composition of leafy
spurge at four growth stages (Fox et al.
1991. N.D. Farm Res.).
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In vitro dry
Growth Crude matter
stages protein Phosphorus digestibility
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- - - - - Percent - - - - - -
Vegetative 27.3 0.53 80
Flowering 23.4 0.46 73
Mature 19.5 0.39 66
Regrowth 15.6 0.32 60
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Recommended Stocking Rates
Proper stocking rates to control leafy spurge vary dramatically between sheep and
goats. Although both classes of livestock readily consume leafy spurge, goats are more
selective than sheep. Dietary overlap between sheep and cattle averages 20 to 35 percent,
but with goats and cattle it is only 5 to 20 percent on leafy spurge infested lands. There
is generally less overlap between the animal species as leafy spurge densities increase.
Average stocking rate of three to four goats per acre of leafy spurge over a four-month
grazing season is required to maintain acceptable control, with lighter stocking rates in
western and heavier rates in eastern North Dakota. For just one month, the goat stocking
rate would be 12 to 16 goats per acre.
To determine stocking rates for a specific time, adjust animal numbers per acre by
dividing the one month stocking rate by number of months intended to graze. Example: if
goats are grazed for 2.5 months, the recommended stocking rate would be 4.8 to 6.4 goats
per acre of leafy spurge (12 goats/2.5 months to 16 goats/2.5 months).
An average stocking rate of one to two sheep per acre of leafy spurge over a four-month
grazing season is required for acceptable control, with lighter stocking rates in western
and heavier rates in eastern North Dakota. Sheep stocking rates for one month would be
four to eight sheep. To determine the stocking rate for a specific time, adjust animal
numbers per acre by dividing the one-month stocking rate by the number of months intended
to graze (see previous example).
Stocking rates should be based on actual infested acreage rather than pasture size.
This will minimize sheep and goat grass consumption, thus allowing optimum grass
production for cattle. Sheep or goat stocking rates could eventually be reduced, while
cattle numbers are increased as leafy spurge densities decline. A four-month grazing
season is recommended because it corresponds with the growing season and is the most
effective and efficient system for leafy spurge control with grazing animals.
Example # 1
Pasture -- 1,000 acres in central North Dakota of which leafy spurge infests 126 acres.
Recommended goat stocking rate for four months = 3.5 goats per leafy spurge acre times
126 acres = 441 goats.
Recommended sheep stocking rate for four months = 1.5 sheep per leafy spurge acre times
126 acres = 189 sheep.
Grazing Management Plan
Sheep and goats should go to pasture earlier than cattle to keep ahead of the early
growing leafy spurge plant. Once leafy spurge has reached 4 to 6 inches of growth, grazing
should begin. In North Dakota, normal turn out date will be approximately mid-May.
NOTE: These recommendations are for leafy spurge infested pastures and apply only to
sheep and goats. Cattle should not go to pasture until range readiness, or around June 1.
Goats, and especially sheep, should be forced to graze leafy spurge in the spring to
improve selectivity, making leafy spurge their dominant food source. Fence off a heavily
infested leafy spurge area with temporary corrals or woven fence and force the sheep or
goats to graze leafy spurge. This practice allows for quick transition and adaptation to
grazing leafy spurge, thus minimizing the potential use of grasses.
There are four management plans to control leafy spurge with sheep or goats. Leafy
spurge control increases with increased grazing intensity.
Plan # 1 -- Seed Removal
Leafy spurge should be grazed during the spring to remove the yellow bracts and
flowering parts of the plant. Grazing may be required again in late summer (late August,
early September) to eliminate potential flowering plants. This type of grazing will
prevent seed-set but does little to reduce the root system.
Plan # 2 -- Multiple Pasture Rotational System
A properly timed rotational grazing system will continuously defoliate leafy spurge
throughout the growing season. Defoliation will eliminate seed production and cause
limited stress on the root system. This plan is often recommended when large leafy spurge
infestations occur over many acres to maximize grazing coverage.
Plan # 3 -- Intensive Rotational Grazing
Leafy spurge should be grazed in the spring until the plant is completely defoliated,
including all flowering parts and green foliage. The sheep or goats should then be rotated
to the next pasture and process repeated. In late summer (late August, September), each
pasture should be grazed a second time and the leafy spurge heavily grazed again.
This method will achieve optimum stress on the plant during the critical growing
periods, decreasing plant vigor and carbohydrate reserves. Grass production increases with
decreased leafy spurge densities.
Plan # 4 -- Continuous Grazing
Continuous grazing (about four months) is the most intensive in terms of leafy spurge
utilization; however, it involves the least amount of labor and fence. Continuous grazing
allows goats or sheep to graze leafy spurge throughout the growing season, continually
stressing the plant. Continuous grazing does not allow a recovery period, maximizing
stress on the root system and its reserves.
Sheep and goats will graze other broadleaf forbs and shrubs, some of which are
beneficial to the plant community, requiring a thorough, careful management plan. Goats
and sheep can dramatically reduce the shrub component (buckbrush, chokecherry, hawthorn,
etc) with a continuous, seasonlong grazing plan. A rotational grazing system may be most
useful when desirable shrub and forb species are present in leafy spurge infested
pastures.
Lease Value for Goats and Sheep for Leafy Spurge Control
It is difficult to determine the cost-effectiveness of sheep or goat grazing for leafy
spurge control. However, one can compare similar grazing control with effective herbicides
as a baseline. For this example, the cost of control with 2,4-D applied twice per year was
used as a baseline. This dollar value will be a minimum value, since long-term grazing
(greater than five years) should reduce leafy spurge infestations greater than 2,4-D
herbicide.
The cost of applying 2 pounds (2 qt) of 2,4-D twice per year was estimated at $18 per
year, including application costs. Since the recommended stocking rate is three to four
goats per acre of leafy spurge for four months, the base lease value of one goat would be
$4.50 to $6.00 ($18 for 2,4-D/3 to 4 goats). If grazing sheep at the recommended stocking
rate of one to two sheep per acre of leafy spurge for four months, the base lease value of
one sheep would be $9.00 to $18.00 ($18 for 2,4-D/1 to 2 sheep).
Chemical control of leafy spurge, when applied properly, only affects broadleaf plants
and shrubs, NOT the grasses. This 2,4-D chemical control is 100 percent efficient for
grass availability for cattle. Average dietary overlap of goats and cattle in leafy spurge
infested pastures at the proper stocking rate is about 10 percent, or a 90 percent (0.9)
efficiency coefficient (100 % efficient -- 10 percent dietary overlap). Average dietary
overlap of sheep and cattle is about 30 percent, or a 70 percent (0.7) efficiency
coefficient (100 % efficient - 30 percent dietary overlap).
Formula for Calculating Lease Value of Sheep
$18.00 (cost of
2,4-D control)
---------------------- X 0.7 (efficiency coefficient)
1.5 to 2.0 (sheep/acre
leafy spurge)
Example # 2
- Using Example # 1 with a pasture size of 1,000 acres and a leafy spurge infestation of
126 acres.
- Using recommended stocking rate of 441 goats at 3.5 goats per acre of leafy spurge for 4
months.
- Lease value per goat: $18.00/3.5 x 0.9 = $4.63 per goat or $1.16 per goat per month.
- Lease value for this property would be $2,041 ($4.63 x 441 goats) over the four-month
grazing season. The cost of controlling one acre of leafy spurge would be $16.20.
Example # 3
- Using Example # 1 with a pasture size of 1,000 acres and a leafy spurge infestation of
126 acres.
- Using recommended stocking rate of 189 sheep at 1.5 sheep per acre of leafy spurge for 4
months.
- Lease value per sheep: $18.00/1.5 x 0.7 = $8.40 per sheep or $2.10 per sheep per month.
- Lease value for this property would be $1,588 ($8.40 x 189 sheep) over the four-month
grazing season. The cost of controlling one acre of leafy spurge would be $12.60.
Goats can provide good control of leafy spurge while increasing grass production for
cattle use. A goat grazing program should allow increased cattle carrying capacity to
levels at or near those achieved before leafy spurge was present.
Sheep can also provide good leafy spurge control, but less grass will be available for
cattle compared to control with goats. Cattle grazing capacity will slowly increase as
fewer sheep are required to control the leafy spurge infestation.
