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Principal investigator Derek
Bailey records cattle locations. |
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SARE Research Synopsis
The overall goal of this project was to determine if selection
had the potential to effectively alter cattle grazing patterns in
rugged rangeland. Specifically our objectives were to: 1) Evaluate
the effect of cattle breed on grazing patterns to determine if some
breeds are more adaptable to mountainous terrain or extensive pastures;
2) determine if removing cattle with undesirable grazing distribution
patterns could result in a more uniform use of forage in foothills
rangeland; and, 3) determine the relationships among individual
grazing distribution patterns and livestock production traits such
as calf weaning weight, pregnancy rate and mature cow weight.
Study sites
Research was conducted at the Thackeray Ranch (part of Northern
Agricultural Research Center) and at the Ross Ranch (cooperating
private ranch owned and managed by Don and Warren Ross), in north
central Montana in the Bear’s Paw Mountains. Topography at
both ranches included steep and gentle slopes. Vegetation was dominated
by perennial cool-season grasses with a few areas of shrubs and
trees. We attempted to use “management-sized” pastures
and cattle herd sizes. At both ranches, study pastures were at least
200 acres and most were 400 acres. Forty to 90 cows grazed in each
pasture.
Treatments
Before the study, cows were observed by researchers on horseback
and ranked by terrain use. Based on previous observations, one half
of each herd was classified as “hill climbers.” Hill
climbers were cows that spent more time grazing steeper slopes and
higher elevations during observations. Cows in the remaining half
of each herd were classified as “bottom dwellers” and
included cows that used gentler slopes and areas closer to water.
At each ranch, hill climbers and bottom dwellers grazed in separate,
but similar, pastures during 1999 to 2001 at the Thackeray Ranch
and 2000 and 2001 at the Ross Ranch. Eight paired comparisons of
hill climbers and bottom dwellers were completed (replicated in
time and space).
Horseback cattle observations
Locations of cattle at the Thackeray Ranch were recorded by horseback
observers during the summers of 1997 through 2001. At the Ross Ranch,
cattle were observed from 1999 to 2001. The procedure used for recording
cattle locations using horseback observers was identical in all
years and study sites. Two to four observers on horseback rode a
pasture during a 1- to 2.5-hour period during the early morning
grazing period (0600 to 0900) and attempted to record the location
of every cow in the pasture. Observers recorded about 87% of the
animals in the herd during an observation period. Cows in each pasture
were observed two to four times each week. These observations were
pooled and used to calculate the average slope, horizontal distance
to water and vertical distance to water for each cow in each pasture
during each year of the study.
Tracking with GPS collars
Some randomly selected cows at the Thackeray Ranch were tracked
using Lotek GPS 2000 collars. These collars recorded cow locations
with an accuracy within 22 feet [13] using the Global Positioning
System (GPS). Cows were tracked for three to 15 consecutive days
based on battery life.
Vegetative measurements
Forage utilization was measured after grazing throughout upland
areas in each set of pastures. Forage stubble heights were measured
in predetermined locations that historically received heavy grazing
use and were considered sensitive areas. These areas included riparian
zones and coulee bottoms.
Statistical Analyses
All comparisons of telemetry data, horseback observations and stubble
heights in sensitive areas between the hill climber and bottom dweller
treatments were based on pasture averages each year. Analyses of
upland forage utilization data compared the relationships between
forage use and terrain use for each treatment.
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