|Abstract or Summary
- A two-year study was made of pastures suspected of inciting
acute bovine pulmonary emphysema (ABPE) in east-central Oregon.
Objectives of this study were (1) to determine the vegetation composition
of these pastures, (2) to determine seasonal trends of tryptophan,
crude protein, and nitrogen/sulfur ratios in selected pasture plants,
(3) to determine daily utilization immediately after cattle were introduced
to these pastures, (4) to relate cattle foraging habits to development
of symptoms of ABPE, and (5) to determine common herd characteristics
and management practices on ranches frequently affected by
Frequency data collected from plant communities on inciting
pastures on the Lemcke and Palmer ranches showed a large number of
species on these meadows. Kentucky bluegrass, Nebraska sedge, and
common rush were common to me sic portions of all pastures studied.
These three species were collected over the 1973 growing season and
analyzed for tryptophan, crude protein and the nitrogen/sulfur ratio.
Tryptophan content decreased from May 24 to September 4, with
the largest change occurring over the first half of the season. It was
determined that a 1000 lb cow eating the forage with the highest tryptophan
level would have to ingest 43.8 kg (dry weight) of material to
assimilate an equivalent amount of a single dose of tryptophan administered
in laboratory induction of ABPE. This amount of forage could
only be ingested over a period of several days.
Crude protein content of Nebraska sedge, common rush, and
Kentucky bluegrass declined from the first sampling to the last and
decreased most rapidly early in the season. Crude protein of all
plants was adequate for lactating range cattle through the soft dough
stages of plants sampled. Crude protein content of Kentucky bluegrass
in latter stages of seed development were not adequate to maintain
lactating range cows.
Nitrogen/sulfur ratios of Nebraska sedge, common rush, and
Kentucky bluegrass varied more than tryptophan or crude protein
within sampling periods. A decrease in nitrogen/sulfur ratios was
noted over the season, the most rapid decline occurring during the
last part. Sulfur content of all samples was adequate to maintain
lactating range cows. No conclusions were drawn concerning the involvement of the nitrogen/ sulfur ratio in ABPE.
Utilization measurements taken on me sic portions of the Lemcke
and Palmer pastures showed Kentucky bluegrass, common rush, and
Nebraska sedge utilized on the Lemcke ranch and birdsfoot trefoil,
Kentucky bluegrass, bluebunch wheatgrass, smooth brome, and
Nebraska sedge selected by cattle on the Palmer ranch. Observations
of grazing habits of cattle on the Lemcke and Palmer pastures in 1972
and 1973 failed to correlate grazing patterns with development of
symptoms of ABPE.
Questionnaires were completed for six ranch operations that had
recent histories of ABPE. Factors common to all six areas were
(1) occurrence of the disease between early July and mid-October,
(2) appearance of symptoms after a change from relatively dry,
sparse to relatively succulent, abundant forage, (3) a natural water
source, (4) apparent high susceptibility of mature, lactating Herefords,
(5) unpredictable morbidity, and (6) high probability of recurrence of
symptoms after ABPE had been diagnosed in a herd.
Determination of cattle diets on ABPE-inciting pastures and
chemical analysis of additional plant species is suggested for future
work. Investigation of summer forage on frequently victimized
ranches and continued compilation of case history information is also