Adverse effect of orally administered magnesium hydroxide on serum magnesium concentration and systemic acid-base balance in adult cattle

Two cows, 1 with diarrhea and 1 with signs of forestomach outflow obstruction, were treated in part with repeated doses of a commercially available antacid/cathartic preparation containing magnesium hydroxide. Both cows subsequently were determined to have hypermagnesemia, along with severe metabolic alkalosis. In addition, each cow was comatose at the time of death. A clinical study was initiated to investigate the causal relationship between the ingestion of magnesium hydroxide and the generation of hypermagnesemia and metabolic alkalosis in adult cows. Twelve healthy mature cross bred beef cows were allotted at random to a fed or fasted (simulated anorexia) group, with 2 untreated and 4 treated cows in each group. A single dose of magnesium hydroxide (1.5 g/kg of body weight, suspended in 3.8 L of warm water) was administered per os to each treated cow, whereas each control cow was given only water. Individual determinations of selected venous blood gas values (plasma bicarbonate ion [HCO3-] concentration, and base excess [BE]), serum magnesium (Mg) concentration, and urine magnesium fractional clearance ratio (Mg-FCR) were made immediately before drug administration, and at 2, 4, 8, 12, 24, and 36 hours after treatment. Compared with control values at the conclusion of the study, mean serum Mg concentration, urine Mg-FCR, plasma HCO3- concentration, and BE were significantly higher (P = 0.0001, P = 0.0015, P = 0.028, and P = 0.021, respectively) in treated cows.(ABSTRACT TRUNCATED AT 250 WORDS)     

Analysis of lidocaine and its major metabolite, monoethylglycinexylidide, in elk velvet antler by liquid chromatography with UV detection and confirmation by electrospray ionization tandem mass spectrometry

A sensitive liquid chromatographic (LC) method with UV detection was developed for the determination of residues of lidocaine (LID) and its major metabolite, monoethylglycinexylidide (MEGX), in elk velvet antler. The drugs were extracted from alkaline velvet antler homogenates, cleaned up on a C(18) solid-phase extraction cartridge, and separated on an Inertsil ODS-3 (3.0 x 250 mm, 5 microm) column using an isocratic mobile phase made up of 0.05 M phosphate buffer (pH 4.0)/acetonitrile (88:12, v/v) at a flow rate of 1.0 mL/min. The limits of quantification for LID and its major metabolite, MEGX, were 10 and 20 ng/g, respectively. The method was validated and used to measure the concentration of residues of LID and MEGX in elk velvet antlers harvested after either LID anesthesia or application of a drug-free control method (electro-anesthesia, EA). No LID or MEGX residues were detected in any of the antlers harvested after EA application. No MEGX residues were detected in any of the velvet antlers harvested after LID application, but residues of LID ranging in concentration from 68 to 4300 ng/g were detected in the three sections of the velvet antlers harvested after LID administration. LC-tandem mass spectrometry was used to confirm the presence of lidocaine detected in the velvet antlers.     

Diagnostic detection methods for Mycobacterium avium subsp. paratuberculosis in white-tailed deer

This study compares the results and suitability of serological testing, microscopic examination, deoxyribonucleic acid (DNA) detection, and bacterial culture for detecting Mycobacterium avium subsp. paratuberculosis (Map) infection in asymptomatic farmed white-tailed deer (WTD) (Odocoileus virginianus). Deer were classified as infected if culture slants from their feces, lymph nodes, or ileum were positive, or if a polymerase chain reaction (PCR) assay detected Map DNA in any of its tissues. Deer identified as positive by agar gel immunodiffusion (AGID) testing or enzyme-linked immunosorbent assay (ELISA) but not by bacterial culture, Ziehl-Neelsen staining, or PCR assay were classified as suspect. Culture of tissues classified 10/16 (62.5%), histopathologic examination 1/16 (6.3%), tissue smears 4/16 (25%), culture slant (CS)-PCR on feces 12/15 (80%), CS-PCR on tissue 13/16 (81.3%), and direct PCR on uncultured tissues 5/16 (31.3%) deer as infected. The ELISA classified 2/15 (13.3%) deer as positive and therefore suspect. The AGID test was negative for all deer. Fifteen of 16 deer were positive by 1 or more tests; only 1 deer was negative on all 11 assays. The CS-PCR gave superior results on antemortem fecal testing as well as postmortem tissue testing and can be recommended for improving the detection of Map in WTD at every stage of infection.     

A survey of the fecal bacteria of bison (Bison bison) for potential pathogens and antimicrobial susceptibility of bison-origin E. coli

An observational study determined the normal fecal bacterial flora of clinically healthy bison, detected the presence of common potential zoonotic pathogens, and determined the antimicrobial susceptibility of isolated E. coli strains. Ninety-six fecal samples from 10 captive herds were cultured for aerobic, anaerobic, facultative, and microaerophillic bacteria. Nineteen major genera of gram-positive and 8 genera of gram-negative bacteria were identified. Salmonella spp. were not detected but some of the isolated bacteria are potential gastrointestinal pathogens. Minimum inhibitory concentrations (MIC) of 24 antimicrobials were determined for the E. coli isolated. Nearly all were susceptible to 23 of the 24 antimicrobials but there was a reduced susceptibility to sulphonamide. There were fewer resistant strains than were reported in recent studies of generic E. coli from cattle living in the same area.     

An observational study of mortality on bison farms in Saskatchewan with special emphasis on malignant catarrhal fever

In December 2011, the Malignant Catarrhal Fever (MCF) Task Force in Saskatchewan recommended that research be conducted on the relationship between the proximity of bison and sheep under typical commercial production settings and bison deaths due to MCF. The objective of this study was to evaluate all causes of death in bison herds and compare the incidence of MCF in herds at varying distances of exposure from sheep operations. Necropsies were completed on 76 of 133 bison reported to have died during the 18-month study period. A total of 7 MCF deaths was reported from 2 large herds within 1.0 km of sheep operations. Although there was a greater risk of MCF deaths in bison herds within 1.0 km of sheep operations than in herds more than 1.0 km away, the overall incidence of MCF deaths within the study period was very low. Most deaths were attributed to non-infectious causes, including copper deficiency.     

Pharmacokinetics and lung and muscle concentrations of tulathromycin following subcutaneous administration in white‐tailed deer (Odocoileus virginianus)

Respiratory tract infections are common in farmed North American white‐tailed deer (Odocoileus virginianus). Tulathromycin is approved for use in cattle but not deer but is often employed to treat deer. The pharmacokinetic properties and lung and muscle concentrations of tulathromycin in white‐tailed deer were investigated. Tulathromycin was administered to 10 deer, and then, serum, lung, and muscle tulathromycin concentrations were measured using liquid chromatography–mass spectrometry (LC–MS). The mean maximal serum tulathromycin concentration in deer was 359 ng/mL at 1.3 h postinjection. The mean area under the serum concentration–time curve, apparent volume of distribution, apparent clearance, and half‐life was 4883 ng·h/mL, 208 L/kg, 0.5 L/h/kg, and 281 h (11.7 days), respectively. The maximal tulathromycin concentration in lung and muscle homogenate from a single animal was 4657 ng/g (14 days) and 2264 ng/g (7 days), respectively. The minimum concentrations in lung and muscle were 39.4 ng/g (56 days) and 9.1 ng/g (56 days), respectively. Based on similarity in maximal serum concentrations between deer and cattle and high lung concentrations in deer, we suggest the recommended cattle dosage is effective in deer. Tissue concentrations persisted for 56 days, suggesting a need for longer withdrawal times in deer than cattle. Further tissue distribution and depletion studies are necessary to understand tulathromycin persistence in deer tissue; clinical efficacy studies are needed to confirm the appropriate dosage regimen in deer.     

Osteochondrosis and epiphyseal bone abnormalities associated with copper deficiency in bison calves

Two bison calves were submitted to the Western College of Veterinary Medicine to confirm suspected copper deficiency. In addition to clinical signs, there were pathologic changes in the cartilage and subchondral bone of several joints. Water analysis indicated high levels of sulfate in the drinking water, contributing to a secondary copper deficiency.