Research Synopsis
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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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