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  • Author or Editor: Arnold M. Saxton x
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Summary

Packed cell volume and plasma total protein (tp), serum albumin (Alb) and globulin (Glb), and plasma ionized calcium (PCa) concentrations, blood viscosity ( bv ), and plasma viscosity (pv) were measured in 42 horses at rest and after the cross country jumping phase of a horse trial competition. The bv and pv were determined at 6 shear rates (230, 115, 46, 23, 11.5, 5.75 s−1), using a digital rotational cone and plate microviscometer. A paired t-test was used to determine differences between pcv, tp, Alb, Glb and PCa values at rest and after exercise. The pcv, tp, Alb, and Glb values increased (P < 0.05) in horses after exercise. The PCa concentration decreased (P < 0.05) in horses after exercise. Mean bv and pv in the 42 horses at rest and after exercise were fitted to an asymptotic function. Significant (P < 0.05) correlation at all shear rates was seen between bv at rest and pcv, tp, Alb, Glb, and PCa values at rest; and between bv after exercise and pcv, tp, Alb, Glb, and PCa values after exercise. Significant correlation was not seen between pv at rest and tp, Alb, Glb, and PCa at rest, or between pv after exercise and tp, Alb, Glb, and PCa concentrations after exercise at any shear rate.

Free access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To evaluate changes in behavior and surfactant protein (SP) A and D concentrations in serum and bronchoalveolar lavage fluid (BALF) samples of calves experimentally infected with Mannheimia haemolytica.

ANIMALS Twelve 4- to 5-month-old Holstein steers.

PROCEDURES Calves were divided into 2 treatment groups and instrumented with a data logger to collect behavioral data. After 10 days of acclimation, calves were experimentally inoculated with 3 × 109 CFUs to 5 × 109 CFUs of M haemolytica suspended in approximately 5 mL of PBS solution (infected calves; n = 6) or 5 mL of PBS solution without M haemolytica (control calves; 6) through a catheter into the right accessory lung lobe. Calves were clinically evaluated twice daily for 7 days after inoculation. Blood and BALF samples were collected from all calves at predetermined times for determination of serum and BALF SP-A and SP-D concentrations. Serum and BALF concentrations of SP-A and SP-D and behavioral data were evaluated over time and between treatment groups.

RESULTS Compared with control calves, infected calves spent more time lying in general and more time lying on the right side during the 24 hours and 6 days after inoculation, respectively. Mean rectal temperature for infected calves (41.3°C) was significantly greater than that for control calves (39.2°C) 12 hours after inoculation. Mean respiratory rate for infected calves (52.5 breaths/min) was significantly greater than that for control calves (45.4 breaths/min) throughout the observation period.

CONCLUSIONS AND CLINICAL RELEVANCE Results indicated continuous behavioral monitoring may improve detection of calves with respiratory tract disease.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To identify the pathogenesis of gastric ulcers by comparing injury to the nonglandular gastric mucosa of horses caused by hydrochloric acid (HCl) or volatile fatty acids (VFAs).

Sample Population—Gastric tissues from 30 horses.

Procedure—Nonglandular gastric mucosa was studied by use of Ussing chambers. Short-circuit current (Isc) and potential difference were measured and electrical resistance calculated for tissues after addition of HCl and VFAs to normal Ringer's solution (NRS). Tissues were examined histologically.

Results—Mucosa exposed to HCl in NRS (pH, 1.5) had a significant decrease in Isc, compared with Isc for mucosa exposed to NRS at pH 4.0 or 7.0. Also, exposure to 60mM acetic, propionic, and butyric acids (pH, 4.0 or 1.5) caused an immediate significant decrease in Isc. Recovery of sodium transport was detected only in samples exposed to acetic acid at pH 4.0. Recovery of sodium transport was not seen in other mucosal samples exposed to VFAs at pH ≤ 4.0.

Conclusions and Clinical Relevance—Acetic, butyric, and propionic acids and, to a lesser extent, HCl caused decreases in mucosal barrier function of the nonglandular portion of the equine stomach. Because of their lipid solubility at pH ≤ 4.0, undissociated VFAs penetrate cells in the nonglandular gastric mucosa, which causes acidification of cellular contents, inhibition of sodium transport, and cellular swelling. Results indicate that HCl alone or in combination with VFAs at gastric pH ≤ 4.0 may be important in the pathogenesis of gastric ulcers in the nonglandular portion of the stomach of horses. (Am J Vet Res 2003;64:404–412)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To identify in vitro effects of hydrochloric acid, valeric acid, and other volatile fatty acids (VFAs) on the pathogenesis of ulcers in the nonglandular portion of the equine stomach.

Sample Population—Gastric tissues from 13 adult horses.

Procedure—Nonglandular gastric mucosa was studied by use of Ussing chambers. Short-circuit current (Isc) and potential difference were measured and electrical resistance and conductance calculated after tissues were bathed in normal Ringer's solution (NRS) or NRS and hydrochloric, valeric, acetic, propionic, and butyric acids. Treated tissues were examined histologically.

Results—Incubation in 60mM valeric acid at pH ≤ 7.0 abruptly and irreversibly abolished Isc, which was followed by a slower decrease in resistance and an increase in conductance. Incubation in 60mM acetic, propionic, and butyric acids and, to a lesser extent, hydrochloric acid at pH ≤ 7.0 significantly decreased Isc, which was followed by an increase in resistance and a decrease in conductance.

Conclusions and Clinical Relevance—Incubation in valeric acid at pH ≤ 7.0 caused a dramatic decrease in mucosal barrier function in the nonglandular portion of the stomach. Changes in barrier function attributable to exposure to valeric acid were associated with histopathologic evidence of cellular swelling in all layers of the nonglandular mucosa. Because of its high lipid solubility, valeric acid penetrates the nonglandular gastric mucosa, resulting in inhibition of sodium transport and cellular swelling. Valeric acid and other VFAs in gastric contents may contribute to the pathogenesis of ulcers in the nonglandular portion of the stomach of horses. (Am J Vet Res 2003;64:413–417)

Full access
in American Journal of Veterinary Research

Abstract

Objectives

To determine the effects of orally administered omeprazole, as enteric-coated capsules, on baseline and stimulated gastric acid secretion in horses.

Animals

5 healthy 8-year-old mixed-breed horses fitted with gastric cannulas.

Procedure

Enteric-coated granules of omeprazole were mixed with corn syrup and administered orally once daily for 5 consecutive days. On days 1 and 5 beginning 5 hours after omeprazole administration, 4 gastric fluid samples were collected, each for 15 minutes, via the gastric cannula (baseline samples). Pentagastrin was administered IV as a constant infusion for the subsequent 2 hours, and 15-minute gastric fluid samples were again collected (stimulated samples). Fluid volume, acidity (mmol H+/L), and pH and gastric acid production (mmol H+) were determined for all baseline samples and for stimulated samples collected during the second hour of pentagastrin infusion. Control experiments were done in a similar manner after giving corn syrup alone to the same horses.

Results

Compared with values obtained during control experiments, baseline and stimulated gastric fluid acidity and gastric acid production significantly decreased, and the mean pH of gastric fluid samples significantly increased, after horses were given 5 daily doses of omeprazole.

Conclusions and Clinical Relevance

Enteric-coated omeprazole (1.0 mg/kg of body weight; PO) administered once daily for 5 days significantly inhibited unstimulated and pentagastrin-stimulated gastric acid secretion in horses. This commercially available formulation of omeprazole may be efficacious in the treatment of gastroduodenal ulcers in horses. (Am J Vet Res 1999;60:929–931)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To measure pH, volatile fatty acid (VFA) concentrations, and lactate concentrations in stomach contents and determine number and severity of gastric lesions in horses fed bromegrass hay and alfalfa hay-grain diets.

Animals—Six 7-year-old horses.

Procedure—A gastric cannula was inserted in each horse. Horses were fed each diet, using a randomized crossover design. Stomach contents were collected immediately after feeding and 1, 2, 3, 4, 5, 6, 7, 8, 10, 12, and 24 hours after feeding on day 14. The pH and VFA and lactate concentrations were measured in gastric juice. Number and severity of gastric lesions were scored during endoscopic examinations.

Results—The alfalfa hay-grain diet caused significantly higher pH in gastric juice during the first 5 hours after feeding, compared with that for bromegrass hay. Concentrations of acetic, propionic, and isovaleric acid were significantly higher in gastric juice, and number and severity of nonglandular squamous gastric lesions were significantly lower in horses fed alfalfa hay-grain. Valeric acid, butyric acid, and propionic acid concentrations and pH were useful in predicting severity of nonglandular squamous gastric lesions in horses fed alfalfa hay-grain, whereas valeric acid concentrations and butyric acid were useful in predicting severity of those lesions in horses fed bromegrass hay.

Conclusions and Clinical Relevance—An alfalfa haygrain diet induced significantly higher pH and VFA concentrations in gastric juice than did bromegrass hay. However, number and severity of nonglandular squamous gastric lesions were significantly lower in horses fed alfalfa hay-grain. An alfalfa hay-grain diet may buffer stomach acid in horses. (Am J Vet Res 2000;61: 784–790)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To compare the effects of hydrochloric acid (HCl) and various concentrations of volatile fatty acids (VFAs) on tissue bioelectric properties of equine stomach nonglandular (NG) mucosa.

Sample Population—Gastric tissues obtained from 48 adult horses.

Procedures—NG gastric mucosa was studied by use of Ussing chambers. Short-circuit current (Isc) and potential difference (PD) were measured and electrical resistance (R) and conductance calculated for tissues after addition of HCl and VFAs (5, 10, 20, and 40mM) in normal Ringer's solution (NRS).

Results—Mucosa exposed to HCl in NRS (pH of 1.5 and, to a lesser extent, 4.0) had a significant decrease in Isc, PD, and R, whereas tissues exposed to acetic acid at a pH of < 4.0, propionic and butyric acids at a pH of ≤ 4.0, and valeric acid at a pH of ≤ 7.0 induced a concentration-dependent effect on reduction in these same values. Values for Isc returned to baseline (recovery of sodium transport) after addition of calcium carbonate in tissues exposed to all concentrations of VFAs except the higher concentrations of valeric acid at a pH of ≤ 4.0. Histologic examination revealed cell swelling in the mucosal layers below and adjacent to the stratum corneum in tissues exposed to HCl and VFAs at a pH of ≤ 4.0.

Conclusions and Clinical Relevance—The VFAs, especially acetic acid, in the presence of HCl at a pH of ≤ 4.0 appear to be important in the pathogenesis of NG mucosal ulcers in horses.

Full access
in American Journal of Veterinary Research

Abstract

Objective

To measure total body water (TBW) content in horses, using deuterium oxide (D20) dilution.

Animals

Six 8- to 10-year-old healthy untrained mixed-breed horses, weighing (mean ± SD) 503.4 ± 64.0 kg.

Procedure

After a 12-hour nonfeeding period, 6 horses were given D2O (0.14 g/kg of body weight) via nasogastric tube. Blood samples were collected from a preplaced indwelling jugular vein catheter prior to and 1 to 8, 10, 12, 14, and 24 hours after administration of D2O. Blood samples were centrifuged immediately, and plasma was collected and stored at −70 C until analysis. The D2O content in plasma was measured by zinc reduction to deuterium gas. The resulting gas was measured, using an isotope ratio mass spectrometer.

Results

Deuterium oxide was rapidly absorbed from the gastrointestinal tract of all horses, and reached peak (mean ± SD) plasma concentration (1,454.4 ± 163 delta D/ml or parts/thousand) 1 hour after administration. Plasma concentration decreased slowly during the next 2 to 3 hours, then remained statistically constant from 2 to 5 hours (early plateau phase) and 3 to 7 hours (late plateau phase) after administration. Mean ± SEM TBW content was 623.0 ± 2.2 ml/kg (62.3% of body weight) for the early plateau phase and 630.3 ± 2.2 ml/kg (63.0% of body weight) for the late plateau phase.

Conclusion

Deuterium oxide dilution appears to be of value for measurement of TBW content in horses, and has a 4-hour plateau effect. Equilibration of D2O with large intestinal water may be the reason for the prolonged equilibrium time and plateau effect seen in these horses.

Clinical Relevance

Deuterium oxide appears safe and efficacious for determining TBW content in horses and may be helpful for determining changes in TBW content during exercise and disease. (Am J Vet Res 1997;58:1060–1064)

Free access
in American Journal of Veterinary Research

Objective—

To establish reference values for urinary diagnostic indices in healthy calves from birth to 90 days of age.

Design—

Prospective field trial.

Animals—

12 Holstein heifer calves.

Procedure—

Urine and serum samples were collected daily for the first 5 days after birth, then weekly until calves were 90 days old. Urine:serum creatinine ratio, urine:serum urea nitrogen ratio, urine:serum osmolality ratio, fractional clearances of sodium and inorganic phosphate, and urine γ-glutamyltransferase activity were measured. Data were grouped by age of calves at the time of sample collection: 1 to 5 days old (neonatal period), 7 to 27 days old (suckling period), and 28 to 90 days old (weanling period).

Results—

Mean urine:serum creatinine, urea nitrogen, and osmolality ratios were significantly higher during the weanling period than during the other 2 periods. There were no significant differences in mean fractional clearances of sodium among age periods.

Clinical Implications—

Urinary diagnostic indices calculated for these healthy calves may be used as reference values for early recognition of renal damage or renal failure. (J Am Vet Med Assoc 1997;211: 212–214)

Free access
in Journal of the American Veterinary Medical Association