Effects of medusahead on beef cale gains Jeremy James 1 , Philip Brownsey 1 , Josh Davy 2 , Theresa Becche 3 , Larry Forero 4 , Mahew Shapero 5 , Emilio Laca 6 1 University of California Sierra Foothill Research and Extension Center, 2 UC Livestock and Natural Resource Advisor Tehama, Glenn and Colusa Counes, 3 UC Livestock and Natural Resource Advisor Stanislaus and San Joaquin Counes, 4 UC Livestock and Natural Resource Advisor Shasta and Trinity Counes, 5 UC Berkeley, 6 Plant Sciences Department UC Davis The issue The invasive grass medusahead dominates millions of acres of rangeland across the West While the ecological impacts of medusahead on rangeland ecosystem funcon have been well-demonstrated the economic impact of this and similar invasive species has never been quanfied , severely liming cost:benefit assessment of different management decisions The objecve of this study is to quanfy the relaonship between medusahead abundance and beef cale gain Approach We experimentally manipulated medusahead abundance in 9, 5-acre pastures for two years (2013-2014) using fire, seeding, herbicide and grazing to reduce medusahead abundance in some pastures while increasing medusahead abundance in other pastures (Fig. 1) In March 2016, we stocked pastures with 6 steers (approximately 650 lbs. starng weight) in each of the 9 pastures Pastures were grazed from March to beginning of May and we adjusted stocking rate (removing or adding animals) to achieve equal ulizaon across pastures by the end of the growing season (target 800 lbs. per acre dry maer) We quanfied forage producon and ulizaon monthly across 10 transects as well as forage composion as frequency (Fig. 1) in mid spring 38% 37% 27% 12% 28% 32% 23% 50% 11% Figure 1. Locaon of the 9 pastures where medusahead composion was experimentally manipulated with values in red indicang medusahead frequency in each pasture (measured in April 2016)
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Effects of medusahead on beef cattle gains Jeremy James1, Philip Brownsey1, Josh Davy2, Theresa Becchetti3, Larry Forero4, Matthew Shapero5, Emilio Laca6
1University of California Sierra Foothill Research and Extension Center, 2UC Livestock and Natural Resource Advisor Tehama, Glenn and Colusa Counties, 3UC Livestock and Natural Resource Advisor
Stanislaus and San Joaquin Counties, 4UC Livestock and Natural Resource Advisor Shasta and Trinity Counties, 5UC Berkeley, 6Plant Sciences Department UC Davis
The issue The invasive grass medusahead dominates millions of acres of rangeland
across the West
While the ecological impacts of medusahead on rangeland ecosystem
function have been well-demonstrated the economic impact of this and
similar invasive species has never been quantified , severely limiting
cost:benefit assessment of different management decisions The objective of this study is to quantify the relationship between
medusahead abundance and beef cattle gain
Approach We experimentally manipulated medusahead abundance in 9, 5-acre pastures
for two years (2013-2014) using fire, seeding, herbicide and grazing to reduce
medusahead abundance in some pastures while increasing medusahead
abundance in other pastures (Fig. 1)
In March 2016, we stocked pastures with 6 steers (approximately 650 lbs.
starting weight) in each of the 9 pastures
Pastures were grazed from March to beginning of May and we adjusted
stocking rate (removing or adding animals) to achieve equal utilization across
pastures by the end of the growing season (target 800 lbs. per acre dry matter)
We quantified forage production and utilization monthly across 10 transects
as well as forage composition as frequency (Fig. 1) in mid spring
38%
37%
27%
12%
28%
32%
23%
50%
11%
Figure 1. Location of the 9 pastures where medusahead composition
was experimentally manipulated with values in red indicating
medusahead frequency in each pasture (measured in April 2016)
Results Average daily gain of steers was higher in March (4.2 lbs/animal/day) than in April (3.1 lbs/
animal/day) but was not associated with variation in medusahead abundance (Fig.2).
Total live stock production per acre over the growing season was significantly negatively
influenced by medusahead abundance (Fig. 3)
On average, for a 10% increase in medusahead abundance, steer gains decreased by over 30
lbs per acre over the grazing season. 2D Graph 3
Medusahead frequency (%)
0 10 20 30 40 50
Ave
rag
e d
aily
ga
in (
lbs. /d
ay)
1
2
3
4
MarchApril
Coefficient Std. Error t P Constant 4.6 0.24 18.8 <0.001Medusahead (%) -0.02 0.01 -1.6 0.147
Medusahead frequency (%)
10 20 30 40 50Liv
esto
ck p
roduction (
lbs. gain
ed/a
cre
/season)
100
200
300
400
Coefficient Std. Error t P Constant 377.1 29.3 12.8 <0.001Medusahead (%) -3.3 0.9 -3.4 0.011
Figure 2. Relationship between medusahead
frequency and steer average daily gains in March
(closed symbols) and April (open symbols)
Figure 3. Relationship between medusahead
frequency and total livestock production per acre
for the grazing season (March to early May).
Research was funded by Western SARE award #EW13-027 and USDA-NIFA Western Regional Integrated Pest Management Program Award #2013-41530-21326 as well as the
UC ANR Sierra Foothill Research & Extension Center grant number 4003
Implications During the most important time of the grazing season where forage
production is exceeding 1,000 lbs per acre per month medusahead appears
to strongly affect steer gains.
The main mechanism in which medusahead decreases gains appears to be
by lowering overall carrying capacity of a pasture rather than an effect on
individual animal gain
At the time steers were shipped, 800-900 lb steers were selling for $1.19
per pound. In this scenario a 10% reduction in medusahead would have
resulted in about a $38 more per acre in market value
This study did not examine effects of medusahead on beef cattle
performance in summer or fall where additional impacts may occur
Modest per acre inputs or changes in management that can progressively
lower medusahead abundance are likely to produce significant economic
