Combined xylazine and ketamine as an analgesic regimen in sheep

OBJECTIVE: To determine whether low dose xylazine with ketamine reduces the concentrations of cortisol and prolactin in sheep postoperatively and to characterise the effects of the drugs on behaviour during recovery. DESIGN: Analysis of variance was used to compare the effects of anaesthesia, surgery and combined ketamine/xylazine treatment on the plasma cortisol and prolactin concentrations and on behavioural variables in pregnant ewes subjected to abdominal surgery. PROCEDURE: Twelve ewes were randomly assigned to receive either ketamine/xylazine or placebo in association with anaesthesia and surgery. Both groups of ewes underwent anaesthesia alone followed a week later by anaesthesia with laparotomy and hysterotomy. Plasma cortisol and prolactin concentrations were assayed during these procedures and for 5 days afterwards. Behavioural observations were made remotely during recovery from anaesthesia and anaesthesia plus surgery. RESULTS: The concentrations of cortisol in the plasma of pregnant ewes undergoing surgery were increased by preoperative handling and the onset of thiopentone/halothane anaesthesia, with a further increase during surgery (P = 0.033). Cortisol concentrations decreased over the first four postoperative hours (P = 0.029) and were normal by 24 h. The drug treatment did not affect the immediate responses of ewes to anaesthesia or surgery, although treated ewes had lower cortisol concentrations than saline-treated controls over the first five postoperative days (P = 0.018). Prolactin concentrations increased in response to anaesthesia (P = 0.047), but were not affected by surgery or the drug treatment. Drug-treated ewes had prolonged sleeping time after surgery (P = 0.002), but they took no longer to stand than saline-treated controls and required fewer attempts to stand successfully (P = 0.025). CONCLUSION: At the doses used, ketamine and xylazine did not mitigate the immediate endocrine consequences of surgery but the behavioural data provide a basis for further investigations that may lead to improvements in analgesic treatments.     

Sedative and analgesic effects of intravenous xylazine and tramadol on horses

This study was performed to evaluate the sedative and analgesic effects of xylazine (X) and tramadol (T) intravenously (IV) administered to horses. Six thoroughbred saddle horses each received X (1.0 mg/kg), T (2.0 mg/kg), and a combination of XT (1.0 and 2.0 mg/kg, respectively) IV. Heart rate (HR), respiratory rate (RR), rectal temperature (RT), indirect arterial pressure (IAP), capillary refill time (CRT), sedation, and analgesia (using electrical stimulation and pinprick) were measured before and after drug administration. HR and RR significantly decreased from basal values with X and XT treatments, and significantly increased with T treatment (p < 0.05). RT and IAP also significantly increased with T treatment (p < 0.05). CRT did not change significantly with any treatments. The onset of sedation and analgesia were approximately 5 min after both X and XT treatments; however, the XT combination produced a longer duration of sedation and analgesia than X alone. Two horses in the XT treatment group displayed excited transient behavior within 5 min of drug administration. The results suggest that the XT combination is useful for sedation and analgesia in horses. However, careful monitoring for excited behavior shortly after administration is recommended.     

The anti-nociceptive and cardiopulmonary effects of extradural fentanyl–xylazine in sheep

Objective To compare the anti‐nociceptive effects of extradural xylazine, fentanyl and a xylazine–fentanyl combination in sheep, and to measure the cardiopulmonary effects of the xylazine–fentanyl combination. Study design Prospective, randomized study. Animals Twenty‐five half‐merino ewes 2–4 years of age and body mass 54.2 ± 1.1 kg. Methods Six sheep in group 1 received 0.2 mg kg^?1 xylazine by extradural injection, six in group 2 received fentanyl 1.5 µg kg^?1 and 13 in group 3 received the combination of both treatments. In all groups, drugs were mixed with saline (0.15 mL kg^?1 before injection). Pulmonary and carotid arterial catheters were placed in seven sheep of group 3 which were used to evaluate cardiopulmonary effects. Anti‐nociception was determined by the response to electrical stimulation (40 V for 1.5 milliseconds) of the left flank and by superficial and deep muscular ‘pinpricking’ stimulation of the pelvic and thoracic limbs and thoracolumbar region. Results Lack of response to electrical stimulation at the left flank was present in 10 ± 1.1 minutes (mean ± SEM) (group 1) and in 4.5 ± 0.5 minutes in group 3. The duration of lack of response to electrical stimulation at the left flank was 96 ± 6 minutes in group 1 and 315 ± 6 minutes in group 3. Responses persisted in group 3. Significant decreases (p < 0.05) in cardiac output 30, 45, 60 and 90 minutes after injection, and in cardiac work at 30 and 45 minutes were observed in the seven animals of group 3. Arterial blood pH was lowest at 90 minutes, arterial bicarbonate was lowest at 60 minutes and values for both arterial and mixed venous base excess increased significantly at 60 and 90 minutes. There was no significant change from baseline values in heart rate, mean arterial blood pressure, respiratory rate, body temperature, systemic vascular resistance, arterial and mixed venous PO₂, PCO₂, oxygen saturation, blood oxygen content, haemoglobin concentration, mixed venous blood bicarbonate and pH. Conclusions Fentanyl decreases the onset time and prolongs the duration of anti‐nociception produced by xylazine. The combination decreases cardiac output but is without significant respiratory effects. Clinical relevance Further studies are required to show that surgery is possible in sheep after extradural xylazine–fentanyl injection.     

The analgesic effects of intrathecal xylazine and detomidine in sheep and their antagonism with systemic atipamezole

OBJECTIVE: To evaluate the analgesic and adverse side effects of intrathecal (IT) xylazine (XYL) and detomidine (DET) and the subsequent effects of two doses of intravenous (IV) atipamezole (ATI). STUDY DESIGN: Prospective, randomized, cross-over. ANIMALS: Five adult healthy female sheep with mean body mass of 55 +/- 2.3 kg. Material and methods Each sheep underwent four treatments: 1) 50 microg kg(-1) XYL IT and 5 microg kg(-1) ATI IV, 2) 50 microg kg(-1) XYL IT and 2.5 microg kg(-1) ATI IV, 3) 10 microg kg(-1) DET IT and 5 microg kg(-1) ATI IV, 4) 10 microg kg(-1) DET IT and 2.5 microg kg(-1) ATI IV. Pain threshold (TH) was tested by applying pulsed and stepwise incremental direct current to the skin overlying the pastern. The current at the point of foot lift was recorded as the TH. Heart rate (HR), mean arterial pressure, arterial oxygen (PO(2)) and carbon dioxide (PCO(2)) tensions were monitored. Outcomes were derived as differences between baseline assessment and measurements after treatment. Two-way anova was used to analyse drug effects, treatment differences between groups were examined with an F-test or Wilcoxon's rank sum test in case of non-parametric data distribution. p was set at 0.05. RESULTS: Both drugs increased the pain TH, caused small increases in PCO(2), and small decreases in HR, the latter was only significant for XYL recipients. Xylazine produced a significantly higher TH, more rapidly and for longer than DET. Atipamezole only significantly affected PaCO(2) in the XYL group 2. The pain TH was not affected in either group after IV ATI. CONCLUSIONS: At the doses used, IT XYL, and to a lesser extent DET, induced pastern analgesia. Atipamezole 5 microg kg(-1) IV antagonized some side effects without affecting analgesia. CLINICAL RELEVANCE: Intrathecal XYL may be useful as an analgesic in sheep. Its safety is increased because IV ATI antagonizes side effects, but not analgesia.     

Comparison of lidocaine, xylazine, and lidocaine−xylazine for caudal epidural analgesia in cattle

Objective To directly compare the time to onset and duration of analgesia produced by a lidocaine/xylazine combination with that produced by lidocaine and xylazine administered alone in the caudal epidural space of dairy cattle. Design Prospective randomized experimental study. Animals Nine adult (> 4 years of age) dairy cows (520–613 kg). Methods Caudal epidural analgesia was produced in all cows with 2% lidocaine (0.22 mg kg^?1; 5.5 mL 500 kg^?1), 10% xylazine (0.05 mg kg^?1 diluted to 5.5 mL 500 kg^?1 with sterile water), and 2% lidocaine/10% xylazine (0.22 mg kg^?1/0.05 mg kg^?1; total volume of 5.7 mL 500 kg^?1), at no earlier than weekly intervals in a Latin square design. Time to onset, duration and cranial spread of analgesia were recorded, as were degree of sedation, ataxia and ptyalism. Results No significant difference (p > 0.05) was noted for time (mean ± SEM) of onset of analgesia between lidocaine (4.8 ± 1.0 minutes) and the lidocaine/xylazine combination (5.1 ± 0.9 minutes) but onset of analgesia following xylazine was significantly longer (11.7 ± 1.0 minutes) than either of the other two treatments. Lidocaine/xylazine (302.8 ± 11.0 minutes) produced analgesia of significantly longer duration than that of xylazine (252.9 ± 18.9 minutes) and both the lidocaine/xylazine combination and xylazine alone produced analgesia of significantly longer duration than that produced by lidocaine (81.8 ± 11.8 minutes). In all cattle, xylazine, administered either alone or with lidocaine, induced mild to moderate sedation and ataxia and cutaneous analgesia from the coccyx to T13. Mild ataxia was also present in those cattle receiving lidocaine alone. Conclusion The combination of xylazine and lidocaine produces analgesia of quicker onset and longer duration than xylazine administered alone and of longer duration than lidocaine administered alone. Clinical relevance Utilizing this combination, long‐duration obstetrical and surgical procedures could commence relatively soon after epidural injection and could be completed without re‐administration of anesthetic agents.     

Effect of choline chloride premedication on xylazine-induced hypoxaemia in sheep

Objective

To determine the anti-inflammatory efficacy of choline in vivo and in vitro and to investigate the anti-inflammatory mechanisms of choline.

A comparison of two intramuscular doses of xylazine-ketamine combination and tolazoline reversal in llamas

OBJECTIVE: To evaluate the anesthetic and cardiorespiratory effects of two doses of intramuscular xylazine/ketamine in llamas, and to determine if an intramuscular injection of tolazoline would shorten the anesthesia recovery time. STUDY DESIGN: Prospective randomized study. ANIMALS: Six castrated male llamas. METHODS: Each llama received a low dose (LD) (0.4 mg kg(-1) xylazine and 4 mg kg(-1) ketamine) and high dose (HD) (0.8 mg kg(-1) xylazine and 8 mg kg(-1) ketamine). Time to sedation, duration of lateral recumbency and analgesia, pulse, respiratory rate, hemoglobin oxygen saturation, arterial blood pressure, blood gases, and the electrocardiogram were monitored and recorded during anesthesia. Three llamas in each treatment were randomized to receive intramuscular tolazoline (2 mg kg(-1)) after 30 minutes of lateral recumbency. RESULTS: Onset of sedation, lateral recumbency, and analgesia was rapid with both treatments. The HD was able to provide at least 30 minutes of anesthesia in all six llamas. The LD provided only 30 minutes of anesthesia in two out of six llamas. Respiratory depression and hypoxemia were seen in the HD treatment during the first 10 minutes of lateral recumbency. Two llamas were severely hypoxemic during this period and were given nasal oxygen for five minutes. Heart rate decreased, but there were no significant changes in blood pressure. Tolazoline significantly shortened the duration of recumbency in the HD treatment. CONCLUSIONS: The HD provided more consistent clinical effects in llamas than did the LD. Intramuscular tolazoline shortens the duration of lateral recumbency in llamas anesthetized with this combination. CLINICAL RELEVANCE: Both doses appear to be very effective in providing restraint in llamas. The LD may be used for procedures requiring a short period of anesthesia or restraint. The HD could be used when a longer duration of anesthesia is desired. Supplemental oxygen should be available if using the HD. Tolazoline (IM) shortened the recovery time with this combination in llamas.     

Effect of caudal epidural xylazine on intraoperative distress and post-operative pain in Holstein heifers

Objective To compare the effects of caudal epidural xylazine versus saline on tolerance of paravertebral nerve block and flank surgery and on post‐operative pain in heifers used for a veterinary student training laboratory. Study design Randomized controlled prospective study. Animals Fourteen one‐year‐old, nongravid, healthy Holstein heifers, weighing 360 ± 5 kg. Methods Xylazine (0.05 mg kg^?1) or 0.9% saline (5 mL) was injected using a caudal epidural technique to seven heifers undergoing a flank surgery. Nerve block of the right paravertebral fossa was performed using equal parts of lidocaine 2% and bupivacaine 0.5%. Heart and respiratory rates, rectal temperature, rumination frequency, and appetite were recorded before and at 4, 8, and 24 hours after surgery. Scores were recorded for: tolerance of local anesthesia injections (pre‐operatively), sedation, ataxia and distress (intraoperatively, every 30 minutes), and pain (4, 8, and 24 hours post‐operatively). Results The animals reaction to local anesthetic injection was judged to be less in the xylazine group by both an experienced observer (p < 0.001) and student surgeons (p < 0.01). The xylazine group required less local anesthetic (82.9 ± 13.8 mL) versus the saline group (108.4 ± 19.6 mL, p = 0.035). Intraoperatively, xylazine heifers were more sedated at all times (p‐values from <0.001 to 0.017), were more ataxic for the first 1.5 hours (p‐values from <0.001 to 0.026), and lower in distress at all times (p‐values from <0.001 to 0.007). No difference in post‐operative pain or physiologic variables was found, except immediately post‐operatively, rectal temperature was higher in the xylazine group (39.5 ± 0.3 °C) than in the saline group (38.6 ± 0.2 °C, p < 0.001). Conclusion and clinical relevance Compared with epidural saline, caudal epidural xylazine reduced distress of anesthetic injection and surgical manipulation in heifers and an improvement in animal well‐being was apparent. This effect may have been as a result of sedation. Pre‐operative epidural xylazine did not appear to improve post‐surgical analgesia in our study.     

Efficacy of caudal epidural injection of lidocaine,xylazine and xylazine plus hyaluronidase in reducing discomfort produced by electroejaculation in bulls

To test the hypothesis that epidural administration of lidocaine, xylazine or xylazine plus hyaluronidase provides reduced pain and stress during electroejaculation in bulls, eight 30-month-old Nellore bulls received saline solution (control), 2% lidocaine, 2% xylazine or 2% xylazine plus hyaluronidase injected into the first intercoccygeal (Co1–Co2) epidural space in randomized order. Heart rate, respiratory rate, mean arterial pressure, analgesia, animal behavior and motor blockade were evaluated before treatment and at predetermined intervals during and after treatment. Pain and stress were scored subjectively, and semen quality was evaluated. The onset of anesthetic action was significantly faster with lidocaine (3.0 ± 1.2 min) than with xylazine or xylazine plus hyaluronidase (8.9 ± 1.5 and 5.5 ± 2.6 min, P=0.021 and P=0.012, respectively), and the onset of anesthesia with xylazine plus hyaluronidase was significantly faster than that with xylazine alone (P=0.032). Treatment with xylazine or xylazine plus hyaluronidase resulted in less discomfort than treatment with lidocaine, as indicated by animal behavior. Changes in heart rate, respiratory rate and arterial pressure were within acceptable limits. Penile protrusion and semen emission occurred in all animals during all four treatments. Our results suggest that xylazine plus hyaluronidase reduced discomfort during electroejaculation more effectively than xylazine or lidocaine alone. Further experiments are necessary to determine whether electroejaculation with xylazine plus hyaluronidase is feasible for obtaining semen from Nellore bulls unaccustomed to being handled or restrained.     

Antinociceptive,physiologic and biochemical effects of electroacupuncture combined with xylazine in hybrid goats

ObjectiveTo elucidate the antinociceptive, physiologic and biochemical effects of electroacupuncture (EA) and xylazine in hybrid goats.Study designProspective experimental study.AnimalsA total of 30 female hybrid goats aged 1–2 years and weighing 25 ± 2.9 kg (mean ± standard deviation).MethodsThe goats were divided into five groups and administered xylazine (0.1 mg kg⁻¹; group XYL.1), xylazine (0.3 mg kg⁻¹; group XYL.3), EA (group EA), EA + xylazine (0.1 mg kg⁻¹; group XYL.1-EA) and 0.9% saline (0.3 mL; control group CON). Nociceptive threshold and serum glucose concentration were measured at time 0 and at 15, 30, 45, 60 minutes and 24 hours after treatment. Nociceptive threshold was measured by passing potassium ions through the skin using potassium iontophoresis. Mean arterial pressure (MAP), heart rate (HR), respiratory frequency (f_R) and rectal temperature (RT) were recorded at times 0 and at 5, 10, 15, 20, 30, 45, 60 minutes and 24 hours. Repeated-measures analyses were performed for each response variable; p < 0.05 was considered significant for all analyses.ResultsAntinociceptive effects in groups XYL.1 and XYL.3 were increased significantly at 15–60 minutes compared with group CON. Antinociceptive effect was higher in group XYL.1-EA than groups XYL.1 or EA at 15–60 minutes (p < 0.05). No significant difference in the nociceptive threshold was recorded in groups XYL.1-EA and XYL.3, except at 30 minutes. HR, MAP, f_R, RT values were higher in group XYL.1-EA than in groups XYL.1 or XYL.3. Serum glucose concentration was higher in group XYL.3 at 15–60 minutes than in CON.Conclusions and clinical relevanceThe XYL.1 and EA combination was effective for antinociception with minimum physiologic alteration, suggesting that the combination may be a new and effective strategy for pain relief during clinical procedures in goats.     

Comparison of two pre-anaesthetic medetomidine doses in isoflurane anaesthetized sheep

OBJECTIVE: To compare the sedative, anaesthetic-sparing and arterial blood-gas effects of two medetomidine (MED) doses used as pre-anaesthetic medication in sheep undergoing experimental orthopaedic surgery. STUDY DESIGN: Randomized, prospective, controlled experimental trial. ANIMALS: Twenty-four adult, non-pregnant, female sheep of various breeds, weighing 53.9 +/- 7.3 kg (mean +/- SD). METHODS: All animals underwent experimental tibial osteotomy. Group 0 (n = 8) received 0.9% NaCl, group L (low dose) (n = 8) received 5 microg kg(-1) MED and group H (high dose) (n = 8) received 10 microg kg(-1) MED by intramuscular (IM) injection 30 minutes before induction of anaesthesia with intravenous (IV) propofol 1% and maintenance with isoflurane delivered in oxygen. The propofol doses required for induction and endtidal isoflurane concentrations (F(E')ISO) required to maintain anaesthesia were recorded. Heart and respiratory rates and rectal temperature were determined before and 30 minutes after administration of the test substance. The degree of sedation before induction of anaesthesia was assessed using a numerical rating scale. Arterial blood pressure, heart rate, respiratory rate, FE'ISO, end-tidal CO2 (FE'CO2) and inspired O2 (FIO2) concentration were recorded every 10 minutes during anaesthesia. Arterial blood gas values were determined 10 minutes after induction of anaesthesia and every 30 minutes thereafter. Changes over time and differences between groups were examined by analysis of variance (anova) for repeated measures followed by Bonferroni-adjusted t-tests for effects over time. RESULTS: Both MED doses produced mild sedation. The dose of propofol for induction of anaesthesia decreased in a dose-dependent manner: mean (+/-SE) values for group 0 were 4.7 (+/-0.4) mg kg(-1), for group L, 3.2 (+/-0.4) mg kg(-1) and for group H, 2.3 (+/-0.3) mg kg(-1)). The mean (+/-SE) FE'ISO required to maintain anaesthesia was 30% lower in both MED groups [group L: 0.96 (+/-0.07) %; group H: 1.06 (+/-0.09) %] compared with control group values [(1.54 +/- 0.17) %]. Heart rates were constantly higher in the control group with a tendency towards lower arterial blood pressures when compared with the MED groups. Respiratory rates and PaCO2 were similar in all groups while PaO2 increased during anaesthesia with no significant difference between groups. In group H, one animal developed a transient hypoxaemia: PaO2 was 7.4 kPa (55.7 mmHg) 40 minutes after induction of anaesthesia. Arterial pH values and bicarbonate concentrations were higher in the MED groups at all time points. CONCLUSION AND CLINICAL RELEVANCE: Intramuscular MED doses of 5 and 10 microg kg(-1) reduced the propofol and isoflurane requirements for induction and maintenance of anaesthesia respectively. Cardiovascular variables and blood gas measurements remained stable over the course of anaesthesia but hypoxaemia developed in one of 16 sheep receiving MED.     

Concentrations of vatinoxan and xylazine in plasma,cerebrospinal fluid and brain tissue following intravenous administration in sheep

ObjectivesTo investigate the extent of vatinoxan distribution into sheep brain, and whether vatinoxan influences brain concentrations of xylazine; and to examine the utility of cerebrospinal fluid (CSF) as a surrogate of brain tissue concentrations for vatinoxan and xylazine.Study designRandomised, blinded, experimental study.AnimalsA total of 14 adult female sheep.MethodsSheep were randomly allocated into two equal groups and premedicated with either intravenous (IV) vatinoxan (750 μg kg^–1, VX) or saline (SX) administered 10 minutes before IV xylazine (500 μg kg^–1). Sedation was subjectively assessed at selected intervals before and after treatments. At 10 minutes after xylazine administration, a venous blood sample was collected and the sheep were immediately euthanised with IV pentobarbital (100 mg kg^–1). Plasma, CSF and brain tissues were harvested, and concentrations of vatinoxan and xylazine were quantified using liquid chromatography–tandem mass spectrometry. Drug ratios were then calculated and the data were analysed as appropriate.ResultsThe brain-to-plasma and CSF-to-plasma ratios of vatinoxan were 0.06 ± 0.013 and 0.05 ± 0.01 (mean ± standard deviation), respectively. Xylazine brain concentrations were not significantly different (835 ± 262 versus 1029 ± 297 ng g^–1 in groups VX and SX, respectively) and were approximately 15-fold higher than those in plasma. The CSF-to-brain ratio of vatinoxan was 0.8 ± 0.2, whereas xylazine concentrations in the brain were approximately 17-fold greater than those in CSF, with and without vatinoxan.Conclusions and clinical relevanceVatinoxan did not significantly affect sedation with xylazine or the concentrations of xylazine in the brain. CSF is not a good predictor of xylazine concentrations in the brain, whereas vatinoxan concentrations were concordant between the brain and CSF, using the dosages in this study.     

Comparative evaluation of sedative and clinical effects of dexmedetomidine and xylazine in dromedary calves (Camelus dromedarius)

ObjectiveTo compare the sedative and clinical effects of intravenous (IV) administration of dexmedetomidine and xylazine in dromedary calves.Study designExperimental, crossover, randomized, blinded study.AnimalsA total of seven healthy male dromedary calves aged 14 ± 2 weeks and weighing 95 ± 5.5 kg.MethodsCalves were assigned three IV treatments: treatment XYL, xylazine (0.2 mg kg⁻¹); treatment DEX, dexmedetomidine (5 μg kg⁻¹); and control treatment, normal saline (0.01 mL kg⁻¹). Sedation scores, heart rate (HR), respiratory rate (f_R), rectal temperature (RT) and ruminal motility were recorded before (baseline) and after drug administration. Sedation signs were scored using a 4-point scale. One-way anova and Mann–Whitney U tests were used for data analysis.ResultsCalves in treatments XYL and DEX were sedated at 5–60 minutes. Sedation had waned in XYL calves, but not DEX calves, at 60 minutes (p = 0.037). Sedation was not present in calves of any treatment at 90 minutes. HR decreased from baseline in XYL and DEX at 5–90 minutes after drug administration and was lower in DEX than XYL at 5 minutes (p = 0.017). HR was lower in DEX (p = 0.001) and XYL (p = 0.013) than in control treatment at 90 minutes. f_R decreased from baseline in XYL and DEX at 5–60 minutes after drug administration and was lower in DEX than XYL at 5 minutes (p = 0.013). RT was unchanged in any treatment over 120 minutes. Ruminal motility was decreased in XYL at 5, 90 and 120 minutes and absent at 10–60 minutes. Motility was decreased in DEX at 5, 10 and 120 minutes and was absent at 15–90 minutes.Conclusion and clinical relevanceThe duration of sedation from dexmedetomidine (5 μg kg^–1) and xylazine (0.2 mg kg^–1) was similar in dromedary calves.     

Pharmacokinetics after intravenous, intramuscular and subcutaneous administration of difloxacin in sheep

The disposition kinetics of difloxacin, a fluoroquinolone antibiotic, after intravenous (IV), intramuscular (IM) and subcutaneous (SC) administration were determined in sheep at a single dose of 5mg/kg. The concentration-time data were analysed by compartmental (after IV dose) and non-compartmental pharmacokinetics method (after IV, IM and SC administration). Plasma concentrations of difloxacin were determined by high performance liquid chromatography with fluorescence detection. Steady-state volume of distribution (V(ss)) and clearance (Cl) of difloxacin after IV administration were 1.68+/-0.21L/kg and 0.21+/-0.03L/hkg, respectively. Following IM and SC administration difloxacin achieved maximum plasma concentration of 1.89+/-0.55 and 1.39+/-0.14mg/L at 2.42+/-1.28 and 5.33+/-1.03h, respectively. The absolute bioavailabilities after IM and SC routes were 99.92+/-26.50 and 82.35+/-25.65%, respectively. Based on these kinetic parameters, difloxacin is likely to be effective in sheep.     

Cardiovascular effects of xylazine and detomidine in horses

The cardiovascular effects of xylazine and detomidine in horses were studied. Six horses were given each of the following 5 treatments, at 1-week intervals: xylazine, 1.1 mg/kg, IV; xylazine, 2.2 mg/kg, IM; detomidine, 0.01 mg/kg, IV; detomidine, 0.02 mg/kg, IV; and detomidine, 0.04 mg/kg, IM. All treatments resulted in significantly decreased heart rate, increased incidence of atrioventricular block, and decreased cardiac output and cardiac index; cardiac output and cardiac index were lowest following IV administration of 0.02 mg of detomidine/kg. Mean arterial pressure was significantly reduced for various periods with all treatments; however, IV administration of 0.02 mg of detomidine/kg caused hypertension initially. Systemic vascular resistance was increased by all treatments. Indices of ventricular contractility and relaxation, +dP/dt and -dP/dt, were significantly depressed by all treatments. Significant changes were not detected in stroke volume or ejection fraction. The PCV was significantly reduced by all treatments. Respiratory rate was significantly decreased with all treatments, but arterial carbon dioxide tension did not change. Arterial oxygen tension was significantly decreased briefly with the 3 IV treatments only.     

Pharmacokinetics after intravenous, intramuscular and subcutaneous administration of moxifloxacin in sheep

The disposition kinetics of moxifloxacin, a fluoroquinolone antibiotic, after intravenous (IV), intramuscular (IM) and subcutaneous (SC) administration was determined in sheep at a single dose of 5 mg/kg. The concentration-time data were analysed by compartmental (after IV dose) and non-compartmental (after IV, IM and SC administration) pharmacokinetic methods. Plasma concentrations of moxifloxacin were determined by high performance liquid chromatography with fluorescence detection. Steady-state volume of distribution (V_ss) and clearance (Cl) of moxifloxacin after IV administration were 2.03 ± 0.36 L/kg and 0.39 ± 0.04 L/h kg, respectively. Following IM and SC administration, moxifloxacin achieved maximum plasma concentration of 1.66 ± 0.62 mg/L and 0.90 ± 0.19 mg/L at 2.25 ± 0.88 h and 3.25 ± 1.17 h, respectively. The absolute bioavailabilities after IM and SC routes were 96.12 ± 32.70% and 102.20 ± 23.76%, respectively. From these data (kinetic parameters and absence of adverse reactions) moxifloxacin may be a potentially useful antibiotic in sheep.     

Comparative study of epidural xylazine or clonidine in horses

OBJECTIVE: To evaluate the cardiorespiratory and behavioural effects of epidural xylazine (XYL) or clonidine (CLO) in horses. STUDY DESIGN: Blinded, randomized experimental study. ANIMALS: Twelve healthy Arabian yearling horses weighing 117-204 kg were randomly allocated into two groups: XYL (n = 6) and CLO (n = 6). METHODS: An epidural catheter was inserted and a facial arterial catheter was placed and the next day the horses were restrained in stocks. Baseline values for heart (HR) and respiratory (RR) rates, arterial pressure and behavioural responses were evaluated before (T0) and 10, 20, 30, 45, 60, 90 and 120 minutes after epidural injection (T10-T120). The horses received 0.2 mg kg(-1) of XYL or 5 microg kg(-1) CLO; adjusted to (3.4 + (body weight in kg x 0.013) mL with saline. Data were analysed by the Kolmogorov-Smirnov test, one-way anova with repeated measures, and one-way anova followed by a Student-Newman-Keuls test or Fisher's exact test, as necessary. Significance was set at p < or = 0.05. RESULTS: Sedation and ataxia were seen at T10, persisting until T120 in four and three horses, respectively, in XYL and all horses in CLO respectively. Two XYL and one CLO horses became recumbent at T45 and T25 respectively. Penile prolapse occurred in four of five males at T30 and T45, in the XYL and CLO groups, respectively, resolving by T120. Tail relaxation was present from T10 to T120 in all horses in XYL and in four horses in CLO. Head drop was observed from T20 to T60 and from T10 to T120 in XYL and CLO respectively. Respiratory rate decreased significantly only at T45 in the CLO group. Heart rate and arterial blood pressure remained stable. CONCLUSIONS AND CLINICAL RELEVANCE: Epidural CLO and XYL produce similar cardiorespiratory and behavioural changes but neither would be safe to use clinically at the doses used in this study.     

Antinociceptive and selected physiological effects of morphine and xylazine on tiletamine‐zolazepam anesthesia in llamas

ObjectiveEvaluate antinociception, anesthesia, and recovery in llamas given tiletamine-zolazepam (TZ) with either morphine, xylazine, morphine and xylazine, or saline.Study designRandomized crossover experimental study.AnimalsSix healthy, adult intact male llamas.MethodsLlamas were given each of four treatments intramuscularly with a 1-week washout: TZ (2 mg kg^?1) combined with either morphine (0.5 mg kg^?1; M), xylazine (0.15 mg kg^?1; X), morphine (0.5 mg kg^?1) and xylazine (0.15mg kg^?1) (MX), or saline (C). Llamas breathed room air during the experiment. Characteristics of anesthesia, recovery, and selected cardiopulmonary variables were recorded. Antinociception was assessed by clamping a claw at 5-minute intervals. Data were analyzed using a mixed-model anova and Tukey-Kramer test, and are expressed as least squares mean ± SEM. Significance was set at p < 0.05.ResultsNo llama in the control group demonstrated antinociception. Antinociception was longest with treatment MX, followed by treatments X and M, respectively. Heart rates in llamas given treatments X and MX were significantly lower than with other treatments. The respiratory rate in llamas given treatment C was greater (p < 0.05) than for all other treatments, however, the respiratory rate was not significantly different among treatments X, M and MX. The PaO₂ for llamas given MX remained <60 mmHg throughout the 20 minute period of blood gas analysis. Mean arterial blood pressure in llamas in treatment MX was less than for treatments M or C.Conclusion and clinical relevanceThe combination of morphine (0.5 mg kg^?1) and xylazine (0.15 mg kg^?1) increased the duration of antinociception compared with xylazine alone, in TZ-anesthetized llamas. Treatments X, M and MX were associated with hypoxemia (PaO₂ < 60 mmHg).     

A gene expression estimator of intramuscular fat percentage for use in both cattle and sheep

Background：The expression of genes encoding proteins involved in triacyglyceride and fatty acid synthesis and storage in cattle muscle are correlated with intramuscular fat（IMF）%.Are the same genes also correlated with IMF%in sheep muscle,and can the same set of genes be used to estimate IMF%in both species？Results：The correlation between gene expression（microarray） and IMF%in the longissimus muscle（LM） of twenty sheep was calculated.An integrated analysis of this dataset with an equivalent cattle correlation dataset and a cattle differential expression dataset was undertaken.A total of 30 genes were identified to be strongly correlated with IMF%in both cattle and sheep.The overlap of genes was highly significant,8 of the 13 genes in the TAG gene set and 8 of the 13 genes in the FA gene set were in the top 100 and 500 genes respertively most correlated with IMF%in sheep,P-value = 0.Of the 30 genes,CIDEA,THRSP,ACSM1,DGAT2 and FABP4 had the highest average rank in both species.Using the data from two small groups of Brahman cattle（control and Hormone growth promotant-treated[known to decrease IMF%in muscle]） and 22 animals in total,the utility of a direct measure and different estimators of IMF%（ultrasound and gene expression） to differentiate between the two groups were examined.Directly measured IMF%and IMF%estimated from ultrasound scanning could not discriminate between the two groups.However,using gene expression to estimate IMF%discriminated between the two groups.Increasing the number of genes used to estimate IMF%from one to five significantly increased the discrimination power;but increasing the number of genes to 15 resulted in little further improvement.Conclusion：We have demonstrated the utility of a comparative approach to identify robust estimators of IMF%in the LM in cattle and sheep.We have also demonstrated a number of approaches（potentially applicable to much smaller groups of animals than conventional methods） to using gene expression to rank animals for IMF%within