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Abstract

Objective—To determine effects after topical administration of latanoprost, timolol, or a commercially available latanoprosttimolol combination twice daily on intraocular pressure (IOP), pupil size (PS), and heart rate (HR) in clinically normal dogs.

Animals—17 clinically normal dogs.

Procedures—A randomized controlled clinical trial was performed with a treatment (n = 9) and saline (0.9% NaCl) solution group (8). Each dog in the treatment group received 3 treatments (latanoprost, timolol, and the latanoprost-timolol combination), with a 14-day washout period between treatments. Baseline values were established on day 1 of each treatment period. On days 2 through 5, drugs were administered topically every 12 hours to 1 eye of each dog in the treatment group. In both groups, IOP PS, and HR were measured at 0, 2, 4, 6, 8, and 9 hours on days 2 and 5.

Results—Eyes treated with latanoprost or the latanoprost-timolol combination had a significant decrease in IOP and a significantly smaller PS, compared with results for dogs receiving only timolol or dogs in the saline solution group. Timolol and the latanoprost-timolol combination both significantly lowered HR, compared with HR following administration of latanoprost and the saline solution.

Conclusions and Clinical Relevance—Topical administration of latanoprost alone was as effective at lowering IOP as was administration of the latanoprost-timolol combination when both were given every 12 hours to clinically normal dogs. Timolol, either alone or in combination with latanoprost, appeared to have little or no effect on IOP in clinically normal dogs but was associated with a reduction in HR. (Am J Vet Res 2010;71:1055–1061)

Full access
in American Journal of Veterinary Research
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate trends in feedlot cattle mortality ratios over time, by primary body system affected, and by type of animal.

Design—Retrospective cohort study.

Animals—Approximately 21.8 million cattle entering 121 feedlots in the United States during 1994 through 1999.

Procedures—Yearly and monthly mortality ratios were calculated. Numbers of deaths were modeled by use of Poisson regression methods for repeated measures. Relative risks of death over time and by animal type were estimated.

Results—Averaged over time, the mortality ratio was 12.6 deaths/1,000 cattle entering the feedlots. The mortality ratio increased from 10.3 deaths/1,000 cattle in 1994 to 14.2 deaths/1,000 cattle in 1999, but this difference was not statistically significant (P = 0.09). Cattle entering the feedlots during 1999 had a significantly increased risk (relative risk, 1.46) of dying of respiratory tract disorders, compared with cattle that entered during 1994, and respiratory tract disorders accounted for 57.1% of all deaths. Dairy cattle had a significantly increased risk of death of any cause, compared with beef steers. Beef heifers had a significantly increased risk of dying of respiratory tract disorders, compared with beef steers.

Conclusions and Clinical Relevance—Results suggested that although overall yearly mortality ratio did not significantly increase during the study, the risk of death attributable to respiratory tract disorders was increased during most years, compared with risk of death during 1994. The increased rates of fatal respiratory tract disorders may also reflect increased rates of non-fatal respiratory tract disorders, which would be expected to have adverse production effects in surviving animals. (J Am Vet Med Assoc 2001;219:1122–1127)

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective

To further validate an antibody-capture ELISA for measuring bovine coronavirus (BCV) exposure (antibody seroresponse) in cattle and to explain the apparent loss of sensitivity of a BCV antigen-capture ELISA when testing feces from adult versus neonatal cattle.

Animals

98 adult cows from herds with and without winter dysentery; 10 gnotobiotic or colostrum-deprived calves.

Procedures

Results of an antibody-capture ELISA for BCV and a plaque reduction virus neutralization assay performed on paired serum samples from 24 cattle were compared with each other and with results of immunoelectron microscopy (IEM) of feces for BCV. For samples from 98 cattle, results of antibody-capture ELISA were compared with results of IEM. Calves were inoculated with feces ELISA-positive or IEM-positive for BCV and monitored for BCV infection. An ELISA was developed to detect BCV antigen-antibody complexes in feces and results were compared with results of an antigen-capture ELISA and IEM.

Results

Antibody-capture ELISA results correlated with neutralization assay results, but agreed more closely with results of IEM. Calves became infected with BCV following inoculation with either ELISA-positive or ELISA-negative but IEM-positive feces. Results of the antigen-antibody ELISA correlated with results of IEM and the antigen-capture ELISA.

Clinical Implications

In adult cattle, testing of paired serum samples by use of an antibody-capture ELISA may be a better indicator of recent BCV exposure than results of virus neutralization tests. Antigen-antibody binding in feces may interfere with results of antigen-capture ELISA for BCV. (Am J Vet Res 1998;59:956–960)

Free access
in American Journal of Veterinary Research

SUMMARY

Two commercially available infectious bovine keratoconjunctivitis (ibk) vaccines were evaluated for their effectiveness in protecting cattle from disease caused by experimental challenge exposure and natural transmission of Moraxella bovis infections. The study was conducted as 2 experiments, using a total of 81 cattle that were culture-negative for M bovis prior to vaccination. In each experiment, young adult cattle were randomly allotted to 4 groups. Each calf in groups 1 and 2 was vaccinated according to the vaccine manufacturer's directions. Groups 3 and 4 were unvaccinated controls. Three weeks after the last vaccination, each calf in groups 1 and 3 was experimentally challenge exposed by dropping a suspension of viable cells of a virulent strain of M bovis directly onto the corneal surface of each eye. Calves in all 4 groups were then commingled in open pastures so that calves in groups 2 and 4 could be naturally exposed to the calves with experimentally induced infections. Each calf was examined for signs of ocular disease on a regular basis by 2 experienced clinicians who scored each eye for severity of disease on the basis of a prearranged scale. Neither clinician was aware of the vaccination or exposure status of the calf nor to which experimental group they belonged. Lacrimal secretions were collected regularly to determine the number of eyes in which the virulent organism became established.

Moraxella bovis with bacterial cultural characteristics similar to those of the virulent strain placed in the eyes of groups 1 and 3 was cultured from ≥ 83% of the eyes of calves in all groups. The incidence of clinical ibk was ≥ 50% in each group. There was no significant difference in the ability of vaccinated calves to resist experimental or natural challenge infection. Compared with that in nonvaccinated controls, no decreased incidence or severity of clinical ibk was noticed in vaccinated calves. Though the challenge strain used was not homologous to those used to prepare the vaccine, it was no different than those that may be expected to cause disease under field conditions.

Free access
in American Journal of Veterinary Research

Summary

Supplementation of selenium and vitamin E to enhance disease resistance in dairy cattle has become common, particularly to prevent periparturient reproductive disorders and mastitis. To establish reference values for serum vitamin E and selenium concentrations in postparturient dairy cattle and to determine whether serum concentrations of these micronutrients varied with season and stage of lactation, cows from a stratified random sample of 50 herds were studied for 1 year. Blood samples were collected from each of the 50 study herds twice, from the 10 most recently parturient cows or from 10% of the herd, whichever was greatest. Mean concentration of vitamin E and selenium was 2.55 μg/ml and 78.12 ng/ml, respectively. Vitamin E concentrations were significantly (P < 0.05) higher during the summer and fall than during the winter and spring. Selenium concentrations were significantly (P < 0.05) lower during the summer and fall than during the winter and spring. Herd, season of blood sample collection, and time since parturition were significant (P < 0.02) in explaining variation in vitamin E and selenium concentrations.

Free access
in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association

SUMMARY

Renal electrolyte and net acid excretion were characterized during generation and maintenance of hypochloremic metabolic alkalosis in a ruminant model. Two phases of renal response with regard to sodium and net acid excretion were documented. An initial decrease in net acid excretion was attributable to increase in bicarbonate excretion with associated increase in sodium excretion. As the metabolic disturbance became more advanced, a second phase of renal excretion was observed in which sodium and bicarbonate excretion were markedly decreased, leading to increase in net acid excretion and development of aciduria. Throughout the metabolic disturbance, chloride excretion was markedly decreased; potassium excretion also decreased. These changes were accompanied by increase in plasma renin and aldosterone concentrations. There was apparent failure to concentrate the urine optimally during the course of the metabolic disturbance, despite increasing plasma concentration of antidiuretic hormone.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To describe structural changes in the left atrioventricular (mitral) valve complex of dogs with endocardiosis by use of scanning electron microscopy.

Animals—5 clinically normal dogs and 4 dogs with mitral valve endocardiosis.

Procedure—The mitral valve complex from each dog was fixed and prepared for examination via scanning electron microscopy. Findings in valves from clinically normal and affected dogs were compared to identify surface changes associated with endocardiosis.

Results—Compared with findings in valves from clinically normal dogs, endocardiosis-affected mitral valve complexes had several morphologic abnormalities. Tissue swelling on the edge of valve leaflets, chordae tendineae, and the chordal-papillary muscle junction was evident. Damage to the valve complex endothelium was unevenly distributed; in some areas, denudation of endothelial cells had exposed the basement membrane or subendothelial valve collagen matrix. This damage was most noticeable on the leaflet edges and extended more to the ventricular aspect of the valve than the atrial side. Cell loss also extended to the chordae tendineae but was less apparent at the chordal-papillary muscle junction. The remaining endothelial cells on affected valves were arranged in less-ordered rows and had more plasmalemmal microappendages, compared with cells on unaffected valves.

Conclusions and Clinical Relevance—Morphologic changes associated with mitral valve endocardiosis in dogs were similar to those observed in humans with mitral valve prolapse. In dogs with mitral valve endocardiosis, gross changes in the valve complex may affect hemodynamics in the heart; alterations in the leaflet and chordal endothelium may contribute to pathogenesis of this disease. (Am J Vet Res 2004; 65:198–206)

Full access
in American Journal of Veterinary Research
in Journal of the American Veterinary Medical Association