Search Results

Abstract

Objective—To calculate values for the total concentration of nonvolatile weak acids (A_tot) 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 A_tot and K _a. Four methods for quantifying the unmeasured strong anion concentration in plasma (anion gap, the Fencl base excess method [BE_ua], 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 A_tot 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 BE_ua ( R ², 0.56), [XA] ( R ², 0.50), and the anion gap ( R ², 0.41).

Conclusions and Clinical Relevance—Calculated values for A_tot, 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)

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.

Abstract

Objective—To determine values for the total concentration of nonvolatile weak acids (A_tot) 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 37^oC 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 K_a from the measured pH and PCO₂ and estimated strong ion difference.

Results—Mean (± SD) values were as follows: A_tot = 24.3 ± 4.6 mmol/L (equivalent to 0.35 mmol/g of protein or 0.76 mmol/g of albumin); K_a = 0.67 ± 0.40 × 10^–7; and the negative logarithm (base 10) of K_a (pK_a) = 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)

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)

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.

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)

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)

Abstract

Objective—To determine the effect of endurance training on QRS duration, QRS-wave amplitude, and QT interval.

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 training.

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)

Abstract

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 calves.

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)

Abstract

Objective—To determine clinical examination findings, clinicopathologic abnormalities, and outcome of treatment in dairy cattle with abomasal impaction.

Design—Retrospective study.

Animals—80 lactating Holstein-Friesian cows ≥ 2 years old.

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)