A trial was conducted May 1 to September 4, 1989 at the Eastern
Oregon Agricultural Research Center (EOARC) Burns, OR to examine the
effects of strip or continuous grazing management on the diet and
performance of steers grazing native flood meadows. The objective was
to determine if strip grazing would be a more efficient means of
grazing management than continuous grazing.
The experiment was designed to test diet quality, botanical
composition of the diet, daily dry matter (DM) intake and performance
of yearling steers. Eighty yearling steers weighing 253±17 kg were
selected from cattle at the Squaw Butte Experiment Station. The
experimental design was a randomized complete block, with blocking
based on past forage production. Treatments were continuous or strip
grazing. A representative meadow of approximately 22.4 ha was divided
into four equal pastures. Continuous grazing steers had access to 5.6
ha pastures for the duration of the study. Animals on strip grazing
were confined to an area that was estimated to provide 5-7 days of
forage using New Zealand portable electric fencing. Strip sizes were
predetermined based on standing forage crop. Steers were not allowed
to graze more than 7 days in any one strip. Diet quality was estimated
from bi-weekly esophageal samples. Extrusa was collected from 4
esophageal fistulated steers per treatment on two consecutive days.
Collections were timed to coincide with the mid point of the strip
being currently grazed. Samples were pooled by collection dates and
analyzed for CP and IVOMD. Dietary OM intake was estimated from biweekly,
24 hr total fecal collections starting the day following
esophageal collections. Total DM fecal output from 6 fecal collection
steers per treatment was corrected with the %IVOMD to predict actual DM
intake. Diet botanical composition was estimated by microhistological
examination of fecal sub-samples. Animal weight gains were recorded
bi-weekly. Experimental animals grazed together at all times during
the trial. Initial stocking densities were 2.0 AU/ha in each treatment
pasture. Steers were counted as .56 AU with 20 steers grazing 5.6 ha
pastures. The average strip size over the trial was .46 ha; and
depending upon standing crop of forage, ranged from .23-1.15 ha.
Record moisture from snowmelt and rainfall resulted in greater than
expected standing crop of forage. This growth resulted in under
stocking of both treatment pastures. A 1.08 ha block was removed as
hay from the higher forage producing strip treatment block to adjust
for over abundant forage. This resulted in a total mean strip grazed
area of 4.37 ha or 22% less than continuous grazing. Actual grazing
density means over the summer were 2.6 AU/ha for continuous and 3.15
AU/ha for the strip treatment. Available forage was determined from
clipped plots on a DM basis and expressed as herbage allowance at a
given point in time. Herbage allowance for steers in continuous grazed
pastures ranged from 405-1153 kg/AU when measured at bi-weekly
intervals and 68-186 kg/AU for strip grazed steers when estimated at
the beginning of each strip. Grazing pressure was higher for strip
grazed steers (.10 AU/kg) compared to continuous (.02 AU/kg). Diet
quality declined significantly over the summer (P<.01). Analysis for
CP in steer diets provided values of 13.9 vs 10.9% for continuous and
strip treatments, respectively. However, this difference was not
significant (P=.14). Digestibility analysis suggested that forage in
continuous diets tended (P=.07) to have higher IVOMD than strip diets
(64.6 vs 60.7%), respectively. Daily herbage intake was similar
(P=.42) for both treatments when expressed as a percentage of body
weight. Diet botanical composition was positively affected by the type
of management system. The amount of the major grass species, meadow
foxtail (Alopecurus pratensjs), was increased (P=.05) 39% in the diet
of strip grazing steers. Differences were noted in the amounts of
other, less frequently occurring grass species. The total amount of
grass tended (P=.06) to be higher in strip diets (49% vs 35% for
continuous). Rushes (Juncus spp.) and sedges (Carex spp.) contributed
a similar percentage to the diets of both treatments. Forbs comprised
less than .5% of the overall diet of both strip and continuous steers.
Individual animal performance tended (P=.09) to be higher under
continuous grazing management. The ADG was 1.16 and .77 kg for steers
in continuous and strip grazing, respectively. However, total animal
production per hectare grazed area (26.14 vs 22.13 kg/hd) was not
considered different (P=.17). / Graduation date: 1991
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/38127 |
| Date | 23 May 1990 |
| Creators | Blount, David Kenneth |
| Contributors | Weber, Dale W. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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