WWRC 92-24
Declining Forage Availability Effects on Utilization and Community Selection by Cattle
Abstract
Land managers of salt desert shrub and sagebrush steppe vegetation
have concerns regarding appropriate stocking rates in summer
for ephemeral stream riparian zones because of elevated levels of
use on woody vegetation. We determined utilization levels of forage
species over time as a fixed animal density decreased available
forage as a means of approximating the stocking rate suitable for
an area and identifying plant species for monitoring. Trend in
abundance of important plant species will ultimately determine
appropriate stocking rate in a particular management situation.
Forage utilization by cattle during mid-summer for 2 successive
years was measured weekly for 3 weeks in streamside (channel and
floodplain) and adjacent upland (terrace and saline upland) vegetation
communities along the ephemeral stream. Measures were
also made of crude protein and dry matter content of plant species.
Plant communities used by cattle were also recorded.
Utilization of streamside and terrace vegetation declined markedly
over the 3 weeks, while utilization of forage in saline uplands was
lower than in other areas and did not decline over weeks of study.
More cattle selected streamside and terrace areas with the most
succulent forages than saline uplands with less succulent forages.
Woody plants in channel areas, cottonwood (Populus deltoides
Bartr. ex Marsh.) particularly, were higher in protein, more succulent,
and more severely grazed than other species. Management of
cottonwood probably limits the stocking rate used in these communities.
Declines in weekly utilization of forages after the first
week indicated intake may have been declining. If so, lower levels
of utilization may be needed to maintain animal performance.
Maintenance of cottonwoods and animal performance considerations
may dictate a lower stocking rate than achieved in this
midsummer study.
Key Words: stocking rate, cottonwood, Populus deltoides, forage
quality, riparian zones
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