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Abstract

Objective—To calculate values for the total concentration of nonvolatile weak acids (Atot) and the effective dissociation constant for nonvolatile weak acids ( K a) 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 experimental studies.

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 K a. 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 volvulus.

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 K a of 7.06. The Atot and K a 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 ( R 2, 0.56), [XA] ( R 2, 0.50), and the anion gap ( R 2, 0.41).

Conclusions and Clinical Relevance—Calculated values for Atot, K a, and the SIG equation should facilitate application of the strong ion approach to acidbase disturbances in cattle. (Am J Vet Res 2002; 63:482–490)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine and compare the effects of erythromycin, neostigmine, and metoclopramide on abomasal motility and emptying rate in suckling calves.

Animals—6 male Holstein calves (15 to 40 days of age).

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 emptying rate.

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)

Full access
in American Journal of Veterinary Research

Abstract

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.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine values for the total concentration of nonvolatile weak acids (Atot) and effective dissociation constant of nonvolatile weak acids (K a) 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)

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in American Journal of Veterinary Research

Abstract

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 mastitis.

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 bacteria.

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)

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in Journal of the American Veterinary Medical Association

Abstract

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.

Full access
in American Journal of Veterinary Research

Abstract

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.

Full access
in American Journal of Veterinary Research

Abstract

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 calves.

Design—Randomized trial.

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)

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in Journal of the American Veterinary Medical Association

Abstract

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.

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in Journal of the American Veterinary Medical Association

Abstract

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; 65:597–603)

Full access
in American Journal of Veterinary Research