Objective—To characterize and compare in vitro contractility
patterns of sections of abomasal wall harvested
from cattle of 3 dairy breeds.
Sample Population—Longitudinal and circular
smooth muscle preparations harvested from the
antrum and body of the abomasum of 30 recently
slaughtered Holstein-Friesian, Brown Swiss, and
Simmental X Red Holstein cows.
Procedure—Spontaneous isometric contractions of
specimens in tissue baths of modified Krebs solution
were recorded during a 4-hour period. Maximal amplitude,
frequency of contractions, and change of basal
tension were used to characterize contractility.
Statistical analyses were used to test for differences
among time periods, among breeds, between specimen
locations, and between fiber orientations.
Results—Myoactivity patterns of abomasal smooth
muscle preparations are highly variable and differ on
the basis of location and fiber orientation. Frequency
of contractions differed significantly among time
periods for longitudinally oriented specimens with
decreasing frequencies of contractions over time.
Maximal amplitude of the longitudinally oriented
specimens from the antrum increased significantly,
whereas maximal amplitude of the circularly oriented
specimens from the antrum decreased significantly.
Values did not differ significantly among
Conclusions and Clinical Relevance—Patterns of
spontaneous contractility of abomasal wall specimens
are not homogeneous. During a 4-hour recording
period, maximal amplitude and frequency of contractions
of specimens varied significantly with
respect to orientation and location; however, spontaneous
contractile myoactivity did not differ significantly
among breeds. Therefore, breed predisposition
for displaced abomasum is not correlated with spontaneous
activity of smooth muscle specimens. (Am J
Vet Res 2002;63:1687–1694)