Objective—To calculate values for the total concentration
of nonvolatile weak acids (Atot) and the effective
dissociation constant for nonvolatile weak acids
( Ka) of bovine plasma and to determine the best
method for quantifying the unmeasured strong anion
concentration in bovine plasma.
Sample Population—Data sets from published and
Procedure—The simplified strong ion model was
applied to published and experimentally determined
values for pH, Pco2, and strong ion difference (SID+).
Nonlinear regression was used to solve simultaneously
for Atot and Ka. Four methods for quantifying the
unmeasured strong anion concentration in plasma
(anion gap, the Fencl base excess method [BEua], the
Figge unmeasured anion method [XA], and the strong
ion gap [SIG]) were compared in 35 cattle with abomasal
Results—For bovine plasma at 37 C, Atot was 25
mM/L, equivalent to 7.6 times the albumin concentration
or 3.6 times the total protein concentration; Ka
was 0.87 × 10–7, equivalent to p Ka of 7.06. The Atot and
Ka values were validated, using data sets from in vivo
and in vitro studies. Plasma unmeasured strong anion
concentration was most accurately predicted in critically
ill cattle by calculating SIG from serum albumin
( R2, 0.66) or total protein concentration ( R2, 0.60),
compared with BEua ( R2, 0.56), [XA] ( R2, 0.50), and the
anion gap ( R2, 0.41).
Conclusions and Clinical Relevance—Calculated
values for Atot, Ka, and the SIG equation should facilitate
application of the strong ion approach to acidbase
disturbances in cattle. (Am J Vet Res 2002;
Objective—To determine the effect of parenteral administration of erythromycin, tilmicosin, and tylosin on abomasal emptying rate in suckling calves.
Animals—8 male Holstein-Friesian calves < 35 days old.
Procedures—Calves received each of 4 treatments in random order (2 mL of saline [0.9% NaCl] solution, IM [control treatment]; erythromycin, 8.8 mg/kg, IM; tilmicosin, 10 mg/kg, SC; and tylosin, 17.6 mg/kg, IM). Calves were fed 2 L of milk replacer containing acetaminophen (50 mg/kg) 30 minutes later. Jugular venous blood samples and transabdominal ultrasonographic abomasal dimensions were obtained periodically after suckling. Abomasal emptying rate was assessed on the basis of the time to maximal plasma acetaminophen concentration and ultrasonographic determination of the halftime of abomasal emptying. One-tailed Dunnett post tests were conducted whenever the F value for group was significant.
Results—Emptying rate was faster for erythromycin, tilimicosin, and tylosin than for the control treatment, as determined on the basis of time to maximal plasma acetaminophen concentration. Ultrasonography indicated that the half-time of abomasal emptying was significantly shorter for erythromycin than for the control treatment. Tylosin and tilmicosin accelerated the abomasal emptying rate, but not significantly, relative to the emptying rate for the control treatment.
Conclusions and Clinical Relevance—Administration of erythromycin, tilmicosin, and tylosin at the label dosage increased abomasal emptying rate in calves. The clinical importance of an increase in abomasal emptying rate in cattle remains to be determined.
Objective—To determine values for the total concentration
of nonvolatile weak acids (Atot) and effective
dissociation constant of nonvolatile weak acids (Ka) in
plasma of cats.
Sample Population—Convenience plasma samples
of 5 male and 5 female healthy adult cats.
Procedure—Cats were sedated, and 20 mL of blood
was obtained from the jugular vein. Plasma was
tonometered at 37oC to systematically vary PCO2
from 8 to 156 mm Hg, thereby altering plasma pH
from 6.90 to 7.97. Plasma pH, PCO2, and concentrations
of quantitatively important strong cations (Na+,
K+, and Ca2+), strong anions (Cl–, lactate), and buffer
ions (total protein, albumin, and phosphate) were
determined. Strong ion difference was estimated
from the measured strong ion concentrations and
nonlinear regression used to calculate Atot and Ka
from the measured pH and PCO2 and estimated
strong ion difference.
Results—Mean (± SD) values were as follows: Atot =
24.3 ± 4.6 mmol/L (equivalent to 0.35 mmol/g of protein
or 0.76 mmol/g of albumin); Ka = 0.67 ± 0.40 ×
10–7; and the negative logarithm (base 10) of Ka (pKa) =
7.17. At 37oC, pH of 7.35, and a partial pressure of CO2
(PCO2) of 30 mm Hg, the calculated venous strong ion
difference was 30 mEq/L.
Conclusions and Clinical Relevance—These results
indicate that at a plasma pH of 7.35, a 1 mEq/L
decrease in strong ion difference will decrease pH by
0.020, a 1 mm Hg decrease in PCO2 will increase
plasma pH by 0.011, and a 1 g/dL decrease in albumin
concentration will increase plasma pH by 0.093.
(Am J Vet Res 2003;64:1047–1051)
Objective—To determine and compare the effects of
erythromycin, neostigmine, and metoclopramide on
abomasal motility and emptying rate in suckling
Animals—6 male Holstein calves (15 to 40 days of
Procedure—Calves were monitored for 1 hour before
being fed milk replacer (60 mL/kg; time, 0 minutes)
and then were monitored for another 3 hours. Calves
received 6 treatments in randomized order: erythromycin
(8.8 mg/kg, IM) at –30 minutes; low-dose
erythromycin (0.88 mg/kg, IM) at –30 minutes; erythromycin
(8.8 mg/kg, IM) at –30 minutes and neostigmine
(0.02 mg/kg, SC) at –30 and 90 minutes; neostigmine
(0.02 mg/kg, SC) at –30 and 90 minutes; metoclopramide
(0.1 mg/kg, IM) at –30 and 90 minutes; and
placebo (2 mL of saline [0.9% NaCl] solution, SC) at
–30 minutes. Abomasal volume was calculated from
ultrasonographic measurements of abomasal width,
length, and height. Abomasal motility and emptying
rate were assessed by measuring luminal pressure
and change in abomasal volume over time.
Results—Administration of erythromycin (8.8 mg/kg)
increased the frequency of abomasal luminal pressure
waves and the mean abomasal luminal pressure
and decreased the half-time of abomasal emptying by
37%. Administration of metoclopramide, neostigmine,
and low-dose erythromycin (0.88 mg/kg) did not
alter abomasal motility, mean luminal pressure, or
Conclusions and Clinical Relevance—Results indicated
that administration of erythromycin at the
labeled antimicrobial dose (8.8 mg/kg, IM) exerted an
immediate, marked prokinetic effect in healthy suckling
calves, whereas administration of metoclopramide
or neostigmine did not alter abomasal motility
or emptying rate. (Am J Vet Res 2005;66:545–552)
Objective—To determine and compare the abomasal emptying rates in calves suckling milk replacer or an isotonic or hypertonic solution of NaHCO3 or glucose.
Animals—5 male Holstein-Friesian calves that were < 30 days of age.
Procedures—Calves were fed 2 L of milk replacer or isotonic (300 mOsm/L) or hypertonic (600 mOsm/L) solutions of NaHCO3 or glucose containing acetaminophen (50 mg/kg). Venous blood samples and transabdominal ultrasonographic abomasal dimensions were obtained periodically after feeding, and abomasal luminal pH was continuously monitored by placement of a luminal pH electrode through an abomasal cannula. Abomasal emptying rate was assessed by the time to maximal plasma acetaminophen concentration, ultrasonographic determination of the half-time of abomasal emptying, and the time for luminal pH to return to within 1 pH unit of the preprandial value.
Results—Hypertonic NaHCO3 solution was emptied slower than an isotonic NaHCO3 solution, isotonic glucose solution was emptied slower than an isotonic NaHCO3 solution, and hypertonic glucose solution emptied slower than an isotonic glucose solution.
Conclusions and Clinical Relevance—An electrolyte solution for oral administration with a high osmolarity and glucose concentration may lead to a slower resuscitation of dehydrated diarrheic calves because such solutions decrease the abomasal emptying rate and therefore the rate of solution delivery to the small intestine. Whether slowing of the abomasal emptying rate in dehydrated diarrheic calves suckling an oral electrolyte solution is clinically important remains to be determined.
Objective—To compare abomasal luminal gas pressure
and volume and perfusion of the abomasum in
dairy cows with a left displaced abomasum (LDA) or
abomasal volvulus (AV).
Animals—40 lactating dairy cows (25 with an LDA
and 15 with an AV).
Procedure—Abomasal luminal gas pressure and volume
and pulse oximetry values for the caudal portion
of the dorsal ruminal sac and abomasal wall were
measured during laparotomy. Abomasal perfusion
was assessed on the basis of abomasal O2 saturation
(pulse oximetry) before correction of the LDA or AV.
Abomasal perfusion was also assessed after correction
of the LDA or AV by measuring venous O2 saturation
in the right gastroepiploic vein and calculating
the abomasal oxygen-extraction ratio.
Results—Abomasal luminal gas pressure and volume
were higher in cattle with an AV than in cattle with an
LDA. Abomasal O2 saturation was lower and abomasal
oxygen-extraction ratio higher in cattle with an AV,
compared with values in cattle with an LDA. In cows
with an AV, lactate concentration in the gastroepiploic
vein was greater than that in a jugular vein, whereas
no difference in lactate concentrations was detected
in cows with an LDA. Abomasal luminal gas pressure
was positively correlated ( r, 0.51) with plasma lactate
concentration in the gastroepiploic vein and negatively
correlated ( r, –0.32) with abomasal O2 saturation
determined by use of pulse oximetry.
Conclusions and Clinical Relevance—Abomasal
perfusion decreases as luminal pressure increases in
cattle with an AV or LDA. ( Am J Vet Res 2004;
Objective—To determine whether results of antimicrobial
susceptibility testing of bacterial pathogens
isolated from the milk of dairy cows with clinical mastitis
were associated with duration of clinical signs or
bacteriologic cure rate following treatment with
cephapirin and oxytetracycline.
Design—Observational study on a convenience sample.
Animals—58 dairy cows with 121 episodes of clinical
Procedure—Cows that only had abnormal glandular
secretions were treated with cephapirin alone. Cows
with an inflamed gland and abnormal glandular secretions
were treated with oxytetracycline and
cephapirin. Cows with systemic signs of illness, an
inflamed gland, and abnormal glandular secretions
were treated with oxytetracycline and flunixin meglumine
and frequent stripping of the affected glands.
The Kirby-Bauer method was used for antimicrobial
susceptibility testing, and current guidelines were
used to categorize causative bacteria as susceptible
or resistant to the treatment regimen.
Results—Median durations of episodes of clinical
mastitis caused by susceptible (n = 97) and resistant
(24) bacteria were not significantly different.
Bacteriologic cure rates at 14 and 28 days were similar
for episodes caused by susceptible and resistant
bacteria; however, for 56 episodes of clinical mastitis
caused by gram-positive bacteria and treated with
cephapirin alone, bacteriologic cure rate at 28 days
was significantly higher for susceptible than for resistant
Conclusions and Clinical Relevance—Results suggest
that antimicrobial susceptibility testing was of no
value in predicting duration of clinical signs or bacteriologic
cure rate in dairy cows with mastitis, except for
episodes caused by gram-positive organisms treated
with intramammary administration of cephapirin
alone. (J Am Vet Med Assoc 2002;221:103–108)
Objective—To determine the effect of endurance
training on QRS duration, QRS-wave amplitude, and
Animals—100 sled dogs in Alaska.
Procedure—Dogs were examined in early
September (before training) and late March (after
training). During the interim, dogs trained by pulling a
sled with a musher (mean, 20 km/d). Standard and
signal-averaged ECG were obtained before and after
Results—Endurance training significantly increased
mean QRS duration by 4.4 milliseconds for standard
ECG (mean ± SEM; 62.3 ± 0.7 to 66.7 ± 0.6 milliseconds)
and 4.3 milliseconds for signal-averaged ECG
(51.5 ± 0.7 to 55.8 ± 0.6 milliseconds) without changing
body weight. Increase in QRS duration corresponded
to a calculated increase in heart weight
(standard ECG, 23%; signal-averaged ECG, 27%).
Signal-averaged QRS duration was correlated with
echocardiographically determined left ventricular diastolic
diameter for the X orthogonal lead (r = +0.41), Y
orthogonal lead (r = +0.33), and vector (r = +0.35).
Training also increased QT interval (234 ± 2 to
249 ± 2 milliseconds) and R-wave amplitude in leads
II and rV2, increased peak-to-peak voltage and S-wave
amplitude in the Y orthogonal lead, and decreased Q-wave
amplitude in the Y orthogonal lead.
Conclusions and Clinical Relevance—Electrocardiographic
changes reflected physiologic cardiac
hypertrophy in these canine athletes in response to
repetitive endurance exercise. The QRS duration
increases in response to endurance exercise training
and, therefore, may be of use in predicting performance
in endurance activities. (Am J Vet Res 2000;61:582–588)
Objective—To characterize the change of pH in the
abomasal lumen throughout a 24-hour period, to
determine whether pH of the abomasal body differs
from pH of the pyloric antrum, and to determine
whether oral administration of cimetidine and ranitidine
alters pH of the abomasal lumen in milk-fed
Animals—5 male dairy calves (4 Holsteins-Friesian, 1
Ayrshire), 5 to 15 days old.
Procedure—Cannulas were surgically positioned in
the abomasal body and pyloric antrum of each calf.
Calves received the following treatments in a randomized
crossover design: milk replacer (60 ml/kg of
body weight, q 12 h [untreated control calves]), milk
replacer and cimetidine (50 or 100 mg/kg, q 8 h), or
milk replacer and ranitidine (10 or 50 mg/kg, q 8 h).
The pH of the abomasal body and pyloric antrum was
measured for 24 hours, using miniature glass pH electrodes.
Results—Suckling of milk replacer immediately
increased abomasal luminal pH from 1.4 to 6.0, followed
by a gradual decrease to preprandial values by
6 hours. Preprandial and postprandial pH values were
not significantly different between the abomasal body
and pyloric antrum, indicating lack of pH compartmentalization
in the abomasum of milk-fed calves.
Administration of cimetidine and ranitidine caused a
significant dose-dependent increase in mean 24-hour
abomasal luminal pH.
Conclusion and Clinical Relevance—Abomasal acid
secretion in milk-fed calves is mediated in part by histamine
type-2 receptors. Cimetidine and ranitidine may
be efficacious in the treatment of abomasal ulcers in
milk-fed calves. (Am J Vet Res 2001;62:1531–1538)
Objective—To determine clinical examination findings,
clinicopathologic abnormalities, and outcome of
treatment in dairy cattle with abomasal impaction.
Animals—80 lactating Holstein-Friesian cows ≥ 2 years
Procedure—Medical records of cattle with abomasal
impaction admitted between 1980 and 2003 were
retrieved, and data were extracted.
Results—All cows were reported to have decreased
food intake; concurrent diseases were identified in 54
(68%). Seventeen cows did not have detectable ruminal
motility, but physical examination findings were
nonspecific and variable. In general, cattle had mild
hypocalcemia, hyperbilirubinemia, and hyperglycemia,
but serum potassium and chloride concentrations
were typically within reference limits. Fifty-five (69%)
cattle had impaction of the pyloric antrum alone, and
25 (31%) had impaction of the abomasal body and
pyloric antrum. Right flank laparotomy and abomasal
massage were performed in 73 cattle. After surgery,
54 (74%) cattle received 3 to 4 L of mineral oil, PO,
daily for 1 to 5 days. Short-term (ie, discharged from
the hospital) survival rate was significantly higher for
cows with impaction of the pyloric antrum alone
(42/45 [93%]) than for cows with impaction of the
body and antrum (12/24 [50%]).
Conclusions and Clinical Relevance—Results suggest
that physical examination findings and results of
serum biochemical analyses do not facilitate the diagnosis
of abomasal impaction in lactating Holstein
cows and that exploratory right flank laparotomy is
necessary to make the diagnosis. Abomasal impaction
should be considered as a differential diagnosis for
inappetence and poor milk production in lactating dairy
cows. (J Am Vet Med Assoc 2005;227:287–291)