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 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 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 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 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 determine the degree of agreement between 2 analyzers for measurement of total CO2 concentration (ctCO2) in equine plasma.
Animals—6 healthy untrained horses, 6 trained Standardbreds undergoing a simulated race protocol, and 135 trained Standardbreds at a racetrack.
Procedures—Jugular venous blood samples were obtained from all horses. Two analyzers (commonly used analyzer A and less expensive analyzer B) were used to measure plasma ctCO2 in each sample. Validation of both analyzers was conducted in accordance with guidelines established by the Clinical and Laboratory Standards Institute and involved characterization of linearity, total analytic error, and bias estimation.
Results—Total analytic error (instrument SD) was 0.58 mmol/L (coefficient of variation, 1.6%) and 0.49 mmol/L (coefficient of variation, 1.4%) for analyzers A and B, respectively, when measuring an aqueous standard containing 36.0 mmol of CO2/L. A 1 g/L decrease in plasma protein concentration corresponded to an increase in ctCO2 measured with analyzer B of 0.065 mmol/L. A difference plot indicated that analyzer B produced values 2.7% higher than analyzer A for 103 samples from the 6 trained and exercised Standardbreds (mean plasma protein concentration, 67 g/L).
Conclusions and Clinical Relevance—Analyzer B provided adequate precision and linearity for measurement of ctCO2 from 5 to 40 mmol/L and was therefore suitable for measuring ctCO2 in equine plasma, provided allowances are made for changes in plasma protein concentration.
Objective—To determine the effects of a commercially
available orally administered antacid agent containing
aluminum hydroxide and magnesium hydroxide
on abomasal luminal pH in clinically normal milkfed
Animals—5 male dairy calves.
Procedure—Throughout the study, calves were fed
milk replacer at 7:30 AM and 7:30 PM. Cannulae for pH
electrodes were placed in the abomasal body and
pyloric antrum. Treatments consisted of oral administration
of a high (50 ml) or low (25 ml) dose of the
antacid agent and oral administration of milk replacer
alone (control). Antacid was given at 7:30 AM, 3:30 PM,
and 11:30 PM, and luminal pH was monitored continuously
for 24 hours, beginning 15 minutes before
administration of the first dose of antacid.
Results—Administration of the first dose of antacid
at the time of the morning feeding resulted in an
increase in mean abomasal body luminal pH of < 1 pH
unit, whereas administration of the second and third
doses of the antacid caused transient (< 3 hours)
increases in mean luminal pH of approximately 1.5
(low dose) and 2.5 (high dose) pH units.
Conclusions and Clinical Relevance—Results suggest
that clinically normal milk-fed calves given a
commercially available antacid agent, PO, will have a
transient increase in abomasal luminal pH. Such
agents may, therefore, have a role in the treatment of
abomasal ulceration in calves; however, the long-term
effects of orally administered antacid agents in milkfed
calves and the clinical efficacy of such agents in
treating abomasal ulceration remain to be determined.
(J Am Vet Med Assoc 2002;220:74–79)
OBJECTIVE To characterize signalment, clinical signs, reproductive history, surgical management, and outcomes of beef cattle undergoing cesarean section because of dystocia at a veterinary teaching hospital.
DESIGN Retrospective case series with nested cohort study.
ANIMALS 173 beef cattle admitted to a veterinary teaching hospital from 2001 through 2010 that underwent cesarean section because of dystocia.
PROCEDURES Medical records were reviewed and information collected on cattle signalment; reproductive history; cause of dystocia; anesthetic protocol; surgical management; number, sex, and body weight of calves delivered (alive or dead); perioperative treatment; duration of hospitalization; and discharge status. A questionnaire regarding postoperative fertility was mailed to all owners, and owners who did not respond were contacted via telephone.
RESULTS Overall mortality rate for calves was high, with 37.6% (62/165) of calves delivered dead or dying ≤ 24 hours after cesarean section. Mortality rate was higher for female versus male calves and for calves from dams with signs of labor for ≥ 3 hours versus < 3 hours before hospital admission. Overall mortality rate for dams was low, with only 10 of 161 (6.2%) dams failing to survive for ≥ 21 days after hospital discharge. Postoperative fertility rate was acceptable, with 75% (44/59) of dams that were rebred after cesarean section giving birth to ≥ 1 live calf.
CONCLUSIONS AND CLINICAL RELEVANCE Cesarean section was a clinically useful method for resolving dystocia in beef cattle, providing a high dam survival rate and an acceptable postoperative fertility rate. Beef cattle producers should seek veterinary assistance whenever clinical signs of dystocia are noticed, preferably within 6 hours after onset of parturition.
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;