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Background -- Tryptophan (Trp) is an essential amino acid that is a precursor of serotonin, a neurotransmitter implicated in sedation, inhibition of aggression, fear and stress in various animal species and humans. Preparations containing Trp are marketed worldwide as calmative agents to treat excitable horses, but there is no evidence of their efficacy. Coupled with this, it has been shown that high oral doses can be toxic. No work has been done to establish that commercial pastes actually increase Trp concentrations in the blood of horses, or how long this elevation lasts. Objectives -- To determine if a commercial Trp oral paste increases plasma Trp concentrations and to establish whether the pharmacokinetics of Trp are altered by different feeding regimens. Design -- Eleven mature geldings (BW 507 ± 12.9 kg) were fed a meal of 2.7 kg lucerne hay at 0900 h each day, supplemented in the afternoon with sufficient hay to meet maintenance energy requirements. At 0900 h the horses were also given either 3 doses of a commercial Trp oral paste (total 6.3 g L-Trp) or an equivalent volume of water in a crossover design. Blood samples were collected every 30 min for 6 h and analysed for total Trp using gas chromatography. The study was repeated after 3 weeks using the same horses fed a morning meal of 1.5 kg oats. Outcomes -- Baseline Trp concentrations measured 2 h after feeding were 71.8 ± 3.7µM and 36.7 ± 3.4 µM for horses fed lucerne hay or oats, respectively (P < 0.001). Peak Trp concentration in response to Trp paste was also higher in horses fed hay (167.6 ± 8.0 µM at 1130 h) versus oats (149.4 ± 13.7 µM at 1030 h; P <0.001), as was the area under a plot of Typ concentration versus time (227.8 ± 8.7 µM.h versus 179.1 ± 14.9 µM.h; P<0.01). Tryptophan concentrations returned to baseline after 6 hours regardless of the ration fed. Conclusion -- No adverse signs were seen in this study although the effect of such doses fed over a more prolonged period is unknown. Tryptophan paste fed at this level does increase plasma Trp concentrations in horses. The amount and duration of this elevation is dependent on the type of diet fed. Further work is needed to determine if the Trp paste fed at lower doses has an effect and whether in fact an increase in Trp concentrations has any effect on equine behaviour. [ABSTRACT FROM AUTHOR]

Background: The pharmacokinetics, efficacy, and safety of meloxicam have been evaluated in adult horses, but not foals. Physiologic differences between neonates and adults might alter drug pharmacokinetics and therapeutic index., Hypotheses: The pharmacokinetics of meloxicam will be different in foals compared with adult horses, and foals could be at increased risk for adverse drug effects., Animals: Twenty lightbreed foals less than 6 weeks of age at commencement of the study., Methods: Single and repeated oral dose pharmacokinetics were determined for meloxicam (0.6 mg/kg) in 10 foals. The safety of the drug was further evaluated in a 2nd group of 10 foals in a randomized blinded prospective study., Results: Plasma concentrations after a single oral dose of meloxicam (0.6 mg/kg) and time to maximum plasma concentration were similar to adult horses. However, drug clearance was much more rapid in foals (elimination half-life 2.48 ± 0.25 hours). Administration of 0.6 mg/kg every 12 hours was well tolerated by foals for up to 3 weeks, with no evidence of drug accumulation in plasma. Adverse effects observed in adult horses at higher dose rates were not observed in foals given 1.8 mg/kg twice daily for 7 days., Conclusions and Clinical Importance: Meloxicam at an oral dose rate of 0.6 mg/kg every 12 hours provided plasma concentrations likely to be therapeutic. In contrast to findings for other NSAIDs, foals appeared more resilient to the adverse effects of this drug than was observed in adult horses., (Copyright © 2013 by the American College of Veterinary Internal Medicine.)

Objective: To determine if postoperative C-reactive protein (CRP) or cortisol concentrations were significantly changed between dogs undergoing ovariohysterectomy by an experienced or inexperienced surgeon. As part of the Charles Sturt University teaching program, 45 bitches from an animal shelter were surgically sterilised between March and October 2010., Methods: The dogs were randomly assigned to surgeons, with 37 sterilised by veterinary undergraduates and 8 by experienced surgeons. Blood samples were collected preoperatively and at 2, 4 and 6 h postoperatively. A standard midline ovariohysterectomy was performed and detailed records kept., Results: The median surgery time for experienced surgeons was 17 min versus 87 min for inexperienced surgeons. Anaesthesia time and blood loss were greater among the inexperienced surgeons. The CRP concentration increased significantly postoperatively for all animals (P < 0.001). Bitches sterilised by inexperienced surgeons had a significantly greater rise in CRP at 4 and 6 h post-surgery (P = 0.046). Serum cortisol concentrations were found to increase significantly over time for all animals (P < 0.001), but were not affected by surgeon experience., Conclusion: The results suggest that inexperienced surgeons affect their patients differently to experienced surgeons, potentially through tissue trauma or anaesthetic duration. The lack of difference in the cortisol concentrations reflects the large number of triggers for cortisol release and, potentially, that there was little difference between the groups in terms of perceived pain in the presence of good analgesia. Serum CRP concentration may be a more sensitive measure than serum cortisol of differences in surgical trauma., (© 2012 The Authors. Australian Veterinary Journal © 2012 Australian Veterinary Association.)

Background: Newer NSAIDs that more selectively target the induced isoform of the cyclooxygenase enzyme (COX2) activity might reduce adverse effects while preserving therapeutic benefits of these drugs., Objectives: To compare the effect of oral administration of multiple dose rates of meloxicam and phenylbutazone (PBZ) on gastric mucosal integrity in horses., Animals: Twenty-five light breed horses., Methods: In vivo toxicity study. Horses were randomly assigned to 5 treatment groups, receiving placebo, PBZ (4.4 mg/kg PO q12h day 1, 2.2 mg/kg PO q12h for 4 days, 2.2 mg/kg PO q24h for 9 days), or 3 dose rates of meloxicam (0.6 mg/kg q24h, 1.8 mg/kg q24h, 3.0 mg/kg q24h) for 14 days. Sucrose permeability testing was performed on Day 0 (before treatment) and on Day 13. All personnel involved with data collection or analysis were blinded to treatment., Results: Administration of PBZ at the above dose rate significantly increased gastric permeability to sucrose, evidenced by increased peak serum sucrose concentrations (280-1,580 pg/μL, P = .001) after treatment. Similar changes were not evident after administration of meloxicam at any dose rate tested, or in control horses (P > .05). Treatment was not associated with significant differences in ulceration of the squamous or glandular mucosa. Peak sucrose concentrations were not correlated with serum total protein or albumin concentrations (R(2) = -0.07, P = .61, R(2) = -0.08, P = .58, respectively)., Conclusion and Clinical Importance: These results suggest that PBZ was associated with greater compromise to gastric mucosal integrity than meloxicam., (Copyright © 2012 by the American College of Veterinary Internal Medicine.)

Determining circulating equine insulin concentrations is becoming increasingly important in equine clinical practice and research. Most available assays are optimized for human medicine, but there is strong equine cross-reactivity because of the highly conserved nature of insulin. To identify an accurate and reliable assay for equine insulin, 6 commercial immunoassays were evaluated for precision, accuracy, and specificity. Only 1 assay initially reached the requisite standard: Mercodia Equine Insulin Enzyme-linked Immunosorbent assay (ELISA). Plasma matrix interferences were identified when the provided assay buffer was used with the Siemens Count-a-Coat Insulin radioimmunoassay (RIA) but not when charcoal-stripped equine plasma was used as the diluent. This modified RIA and the Mercodia Equine Insulin ELISA were evaluated further by directly examining accuracy by comparing their results for 18 equine plasma samples with values obtained using liquid chromatography and high-resolution/high-accuracy mass spectrometry (LC-MS). Compared with LC-MS measurements, the modified Siemens Insulin RIA rendered a moderate Lin's concordance coefficient (ρ(c)) of 0.41, whereas the Mercodia Equine Insulin ELISA rendered a very poor ρ(c) of 0.06. This suggests that the Siemens Insulin RIA is appropriate to use for routine evaluations when LC-MS is not available., (Copyright © 2011 Elsevier Inc. All rights reserved.)