BOTTOM LINE by tyndale


									                                      Cattle Range Site Preference Using
                                      GPS/GIS Technology
                                      R.K. Lyons, R.V. Machen, and C. Nicklas

                                          position of each animal within 5-10       Furthermore, some areas within the
BOTTOM LINE                               yards of their actual location after      Rumple-Comfort soil were favored
                                          differential correction. Collars were     over the total area occupied by this
! Strong cow preference for soil          also equipped with an ambient             soil type. For example, in the April
types could      increases    grazing     temperature sensor and vertical and       trial, Map Sites 3 and 4 which were
pressure.                                 horizontal motion sensors. Field          within the Rumple-Comfort soil type
                                          observations were conducted to            accounted for 38% of the total
! Rock cover greater than 30%             interpret data from the motion            position fixes and 50% of the
almost completely deterred cow use.       sensors. Motion data provides an          Rumple-Comfort position fixes.
                                          indication of whether cows were           These two map sites made up about
! Brush management decisions              grazing or resting. Data was collected    9% of the pasture area available
should consider rock cover.               during five six-day trials at 15-minute   during the April trial. Distribution
                                          intervals for a total of about 576        patterns for the April trial are
                                          position fixes per cow per trial.         illustrated in Figure 1. In the Mid-
                                              ArcView Global Information            August trial, Map Site 4 alone
           Introduction                   System (GIS) software was used to         accounted for 48% of the total
                                          project cow position fixes onto digital   position fixes and 80% of the fixes
     Research has demonstrated that       aerial photographs. ArcView was also      within the Rumple-Comfort soil. This
cattle and other grazing livestock do     used to quantify use of areas within      map site made up about 12% of the
not always distribute themselves          pastures in terms of position fixes per   pasture area available during the Mid-
evenly across a pasture and, therefore,   acre. Within pastures, brush density,     August trial.
do not evenly use the forage within       rock cover, and distance to water              When analyzed over the whole
the pasture. The purpose of this study    were measured within areas of use         range of rock cover (almost zero to 48
was to examine cattle distribution        and non-use. Overall use between the      percent), rock cover was the only
patterns, to find reasons for these       two major soil types on the study         variable of the three considered (rock
patterns, to find potential solutions     ranch was analyzed statistically using    cover, brush density, and distance to
for these distribution problems, and to   analysis of variance. Effects of rock     water) that explained cow use of
show these patterns pictorially to        cover, brush density, and distance to     areas. This one variable explained 63
illustrate grazing distribution           water were analyzed using regression      percent of the variation in cow use
concepts in Extension publications        analysis.                                 (Figure 2). Essentially no use
and at educational events.                                                          occurred above 30 percent rock
                                                Results and Discussion              cover.
     Experimental Approach                                                               Below 10 percent rock cover,
                                               On average, almost 3 times as        both rock and brush helped explain
    This study was conducted on a         many position fixes (p=0.01) were         cow use when considering total
ranch in the eastern Edwards Plateau.     located in the Rumple-Comfort soil        (grazing and non-grazing) position
Four mature cows were fitted with         type as in the Comfort soil type          fixes per acre, grazing position fixes,
Lotek 2000 Global Positioning             (Table 1). Within each of the five        and non-grazing position fixes. In
System (GPS) Collars. These collars       trials, position fixes per acre were      addition, when only grazing position
were capable of estimating the            significantly greater for the Rumple-     fixes were considered, distance to
                                          Comfort soil type (Table 1).              water negatively influenced cow use.

Interestingly, brush density had a         Table 1. Comparison of average differentially corrected position fixes per acre
positive influence on cow use when         for cows within the Rumple-Comfort and Comfort soil types.
rock cover was below 10 percent.
      A strong preference for the
                                                                                         Position Fixes/acre
Rumple-Comfort over the Comfort
soil type was exhibited by cows in             Trial                              Rumple-            Comfort           Probability
this study. In addition, there were                                               Comfort
preferred areas within the Rumple-
Comfort soil type. These preferences           Overall                            1.25               0.43              0.01
can lead to overuse. Fencing
preferred areas separately is a                Mar-Apr                            2.61               O.97              <0.0001
potential means of preventing                  April                              0.64               0.16              0.0156
overuse. If separate fencing is not
feasible, other options include                May                                1.08               0.24              <0.0001
rotational grazing and reduced stock
densities and stocking rates.                  Mid-Aug                            0.89               0.48              0.002
      Rock cover above 30 percent              Late-Aug                           1.01               0.32              0.0001
appeared to almost completely deter
cow use of an area. In contrast, brush
appeared to have a positive influence
on cow use when rock cover was
below 10 percent. This observation
may seem confusing. However, most
dense brush also tended to be
associated with dense rock.
Therefore, at lower brush densities
and low rock cover, cows were
probably attracted to the brush for
shade and grazing.
      While dense brush is a deterrent
to grazing by cows, results from this
study indicate that brush management
decisions related to increasing
grazing for cows also needs to
include consideration of rock cover.                   Figure 1. Grazing distribution patterns within the
For example, in this study, some of                    Rumple-Comfort (RC) and Comfort (CR) soil types for
the highest rock cover was in an open                  the April trial.
area close to water. However, this
area had very few position fixes.                                           100
Therefore, even if brush were                                                                               r2=0.63
removed from heavily wooded areas
                                                          Relative Use, %

associated with high rock cover, these                                       60
areas would probably receive little
cow use. Heavily wooded areas                                                40
associated with high rock cover are
probably best left for wildlife habitat.                                     20
Because these kinds of areas provide                                          0
little potential benefit to cows, they
should not be included when                                                 -20
considering the cow carrying                                                      0      10     20    30          40      50
capacity.                                                                                     Rock Cover, %

                                                         Figure 2. Relationship between rock cover and cow
                                                         use. Rock cover explained 63% of the variability.

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