Cervical spinal kinematics: a comparison between foals and adult horses

A photographic method was used to measure axial rotation, dorsoventral flexion and extension and lateral bending at each intervertebral joint complex from the occiput to the first thoracic vertebra in spinal segments from 19 foals under 12 months of age and 14 horses over three years of age. Comparisons between the two groups showed that there was a general reduction in cervical spinal mobility with age. For the three types of movement at the eight joints tested, adults' mobility exceeded that of foals in only three cases (axial rotation and lateral bending at the A-O joint, and lateral bending at C7-T1). These differences were not significant (P greater than 0.05). In the remaining 21 cases the amplitude of movement was greater in the foals, the differences being significant (P less than 0.05) in 16 cases. With regard to overall mobility of the cervical spine the foals exceeded the adults by 17.3 per cent for axial rotation, 22.0 per cent for dorsoventral flexion and extension and 18.7 per cent for lateral bending.     

Pharmacokinetics and pharmacodynamics comparison between subcutaneous and intravenous butorphanol administration in horses

The study objective was to compare butorphanol pharmacokinetics and physiologic effects following intravenous and subcutaneous administration in horses. Ten adult horses received 0.1 mg/kg butorphanol by either intravenous or subcutaneous injections, in a randomized crossover design. Plasma concentrations of butorphanol were measured at predetermined time points using highly sensitive liquid chromatography–tandem mass spectrometry assay (LC‐MS/MS). Demeanor and physiologic variables were recorded. Data were analyzed with multivariate mixed‐effect model on ranks (P ≤ 0.05). For subcutaneous injection, absorption half‐life and peak plasma concentration of butorphanol were 0.10 ± 0.07 h and 88 ± 37.4 ng/mL (mean ± SD), respectively. Bioavailability was 87%. After intravenous injection, mean ± SD butorphanol steady‐state volume of distribution and clearance was 1.2 ± 0.96 L/kg and 0.65 ± 0.20 L/kg/h, respectively. Terminal half‐lives for butorphanol were 2.31 ± 1.74 h and 5.29 ± 1.72 h after intravenous and subcutaneous administrations. Subcutaneous butorphanol reached and maintained target plasma concentrations >10 ng/mL for 2 ± 0.87 h (Mean ± SD), with less marked physiologic and behavioral effects compared to intravenous injection. Subcutaneous butorphanol administration is an acceptable alternative to the intravenous route in adult horses.     

Energy and protein supply for event horses during training: comparison between intake and requirements

In horses that exercise intensively (for example, event horses in training) the intake and energy requirements were compared on the basis of a diet record and estimates of energy required for exercise. Daily net energy intake over a 7 days period was on average 30% (n = 15) higher than the net energy requirement. Since the horses had a constant body weight, and thus were in energy balance, the energy intake was overestimated and/or the energy requirement was underestimated. The intake of digestible protein was 92% higher than the protein requirement. This study illustrates the problems concerning ration assessment and evaluation in practice.     

Genetic connections between dressage and show-jumping horses in Dutch Warmblood horses

Abstract

During the last decades, the breeding practice within the Dutch Warmblood studbook (KWPN) has resulted in an increasing specialisation of horses into show-jumping (JH) and dressage (DH). The objective of this study was to describe the effect of the specialisation on the connectedness between the subpopulations of JH and DH horses registered by KWPN. The subpopulations comprised 23,800 JH horses and 18,125 DH horses, born between 1995 and 2009. Genetic similarity (GS), genetic pool in common (GC_x) based on the marginal genetic contribution of common ancestors and coefficient of relationship (r) between and within subpopulations were analysed in three periods of time to describe changes in genetic connectedness between subpopulations. A decline in GS (0.97–0.45), GC_0.5 (0.69–0.13) and r (0.018–0.014) in the recent years was observed. Both subpopulations have a common genetic pool; however, if the specialisation process continues, it will result in two unrelated (genetic) groups.     

A comparison of xylazine-ketamine and detomidine-ketamine anaesthesia in horses

Anaesthesia produced by xylazine (1.1 mg/kg IV) followed in 3–5 minutes by ketamine (2.2 mg/ kg IV) (X / K) was compared to anaesthesia produced by detomidine (0.02 mg/kg IV) followed in 15–25 minutes by ketamine (2.2 mg/kg IV) (D/K) in the same six horses. Quality of induction, recovery, muscle relaxation, coordination (before and after anaesthesia) and response to stimulus were subjectively evaluated. Heart rate, respiratory rate, mean blood pressure, hemoglobin saturation, arterial pH, CO₂ and O₂ were monitored. Recumbency time and number of attempts required to stand were recorded. Recumbency time was longer in all horses with X/K (median recumbency time of 27 min) than with D/K (median recumbency time of 22 min). No significant differences between treatments were seen for any other variable measured, although 2 horses did not appear to reach a surgical plane of anaesthesia with D/K.     

Clinical comparison of xylazine and medetomidine for premedication of horses

OBJECTIVE: To compare the analgesic and cardiopulmonary effects of medetomidine and xylazine when used for premedication of horses undergoing general anesthesia. DESIGN: Randomized clinical trial. ANIMALS: 40 horses. PROCEDURE: Twenty horses were premedicated with medetomidine (10 microg/kg [4.5 microg/lb], i.m.) and the other 20 were premedicated with xylazine (2 mg/kg [0.9 mg/kg], i.m.). Horses were then anesthetized with a combination of guaifenesin and ketamine; anesthesia was maintained with halothane. Additional doses of medetomidine or xylazine were given if horses were not sufficiently sedated at the time of anesthetic induction. After induction of anesthesia, sodium pentothal was administered as necessary to prevent limb movements. Hypotension was treated with dobutamine; hypoventilation and hypoxemia were treated with intermittent positive-pressure ventilation. The quality of anesthetic induction, maintenance, and recovery and the quality of the transition to inhalation anesthesia were scored. RESULTS: Scores for the quality of the transition to inhalation anesthesia were significantly higher for horses premedicated with medetomidine than for horses premedicated with xylazine. However, other scores, recovery times, and numbers of attempts needed to achieve sternal recumbency and to stand were not significantly different between groups. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that medetomidine is suitable for premedication of horses undergoing general anesthesia. Analgesic and cardiopulmonary effects of medetomidine were similar to those of xylazine, except that the transition to inhalation anesthesia was smoother when horses were premedicated with medetomidine, rather than xylazine.     

Fibrinogen level in clinically healthy horses]

Various sets of horses were examined in view of the necessity of widening the range of biochemical substances for diagnostic purposes in the field of veterinary medicine. The aim of the investigations was to obtain basic information on fibrinogen level and its variability. The average value stated was 280 mg% s = 89, sx = 12, V% = 32). The fibrinogen level in horses of the pronounced oxidation type was lower than in those with reduced metabolism, the difference being connected with the speed of sedimentation of erythrocytes. Repeated examination of a part of the set of horses (n = 10) on three different days within one week under the same conditions, showed a nonsignificant difference in the variability of the investigated horses (F = 0.901); neither did the coefficient of repeatability (rop = 0.11) reach the level of the testing criterion. The results indicate variability, with normal physiological condition of the animal, in the fibrinogen level. The physiological variability in fibrinogen level can also be explained in connection with other protein fractions.     

A comparison between the nutritive value of short-cutting cycle, high temperature-dried alfalfa and timothy hay for horses.

The objective was to evaluate the nutritive value of short-cutting cycle, high temperature-dried (SCCHTD) alfalfa compared to timothy hay. This was achieved by carrying out 4 x 4 Latin Square digestibility trial using 4 Thoroughbred (one three-quarter Thoroughbred) horses (mean liveweight, 531 kg). The four dietary treatments were 0AA (timothy hay only), 33AA (0.33 alfalfa: 0.67 timothy hay), 67AA (0.67 alfalfa: 0.33 timothy hay) and 100AA (alfalfa only). Digestibility data were obtained by using acid-insoluble ash to estimate apparent digestibility coefficients of nutrients. Rate of passage of the feedstuff was determined using chromium-mordanted hay. Plasma triglyceride and cholesterol concentrations were estimated. The digestibilities of organic matter (0.63), energy (0.57) and crude protein (0.74) of the alfalfa were significantly (P less than 0.001) higher than those for the hay (0.45, 0.43 and 0.36 respectively). The fibre components of alfalfa and hay were digested to the same extent but the ether extract of alfalfa was less well digested. Alfalfa saponins had no consistently significant effects on plasma cholesterol and triglyceride values but may contribute to the negative digestibility of alfalfa ether extract. We conclude that SCCHTD alfalfa is of much higher nutritive value than timothy hay when fed to Thoroughbred horses.     

Thyroid hormone concentrations differ between donkeys and horses

Reasons for performing study: Reference intervals for thyroid hormones (TH) concentrations have not been previously established for donkeys, leading to potential misdiagnosis of thyroid disease. Objectives: To determine the normal values of TH in healthy adult donkeys and compare them to TH values from healthy adult horses. Methods: Thirty‐eight healthy Andalusian donkeys and 19 healthy Andalusian horses from 2 different farms were used. Donkeys were divided into 3 age groups: <5, 5–10 and >11 years and into 2 gender groups. Serum concentrations of fT3, tT3, rT3, fT4 and tT4 were quantified by radioimmunoassay. All blood samples were collected the same day in the morning. None of the animals had received any treatment for 30 days prior to sampling or had any history of disease. Both farms were in close proximity and under similar management. Differences between groups were determined using a one‐way ANOVA analysis followed by Fisher's LSD test. P<0.05 was considered significant. Results: Serum TH concentrations were higher in donkeys than in horses (P<0.01). Donkeys <5 years had higher serum rT3, fT4 and tT4 concentrations than donkeys >5 years (P<0.05). Furthermore, older donkeys (>11 years) had lower serum fT3 and tT3 concentrations than younger donkeys’ groups (<5 and 5–10 years, P<0.05). TH concentrations were not different between genders (fT3: P = 0.06; tT3: P = 0.08; rT3: P = 0.15; fT4: P = 0.89; and tT4: P = 0.19). Conclusions: Thyroid hormone concentrations are different between healthy adult donkeys and horses. Potential relevance: Establishing species‐specific TH reference ranges is important when evaluating clinicopathologic data in equids in order to avoid the misdiagnosis of thyroid gland dysfunction. Further studies to elucidate the physiological mechanisms leading to these differences are warranted.     

Pharmacokinetics of chloramphenicol base in horses and comparison to compounded formulations

Chloramphenicol is commonly used in horses; however, there are no studies evaluating the pharmacokinetics of veterinary canine‐approved tablets. Studies using different formulations and earlier analytical techniques led to concerns over low bioavailability in horses. Safety concerns about human health have led many veterinarians to prescribe compounded formulations that are already in suspension or paste form. The objective of this study was to evaluate the pharmacokinetics of approved chloramphenicol tablets in horses, along with compounded preparations. The hypothesis was that chloramphenicol has low absorption and a short half‐life in horses leading to low serum concentrations and that compounded preparations have lower relative bioavailability. Seven horses were administered chloramphenicol tablets (50 mg/kg orally). In a crossover design, they were administered two compounded preparations to compare all three formulations at the same dose (50 mg/kg). C_max was 5.25 ± 4.07 μg/ml at 4.89 hr, 4.96 ± 3.31 μg/ml at 4.14 hr, and 3.84 ± 2.96 μg/ml at 4.39 hr for the tablets, paste, and suspension, respectively. Elimination half‐life was 2.65 ± 0.75, 3.47 ± 1.47, and 4.36 ± 4.54 hr for tablets, paste, and suspension, respectively. The AUC_0→∞ was 17.93 ± 7.69, 16.25 ± 1.85, and 14.00 ± 5.47 hr*μg/ml for the tablets, compounded paste, and compounded suspension, respectively. Relative bioavailability of compounded suspension and paste was 78.1% and 90.6%. C_max after administration of all formulations did not reach the recommended MIC target of 8 μg/ml set by the Clinical Laboratory Standards Institute (CLSI) for most bacteria. Multidose studies are warranted, but the low serum concentrations suggest that bacteria with MIC values lower than CLSI recommendations should be targeted in adult horses.     

马传染性贫血弱毒疫苗免疫马与自然感染马酶联免疫吸附试验血清抗体耐热性比较研究

本试验对马传贫血清抗体酶联免疫吸附试验(ELISA)的耐热性进行了比较研究.对2匹弱毒疫苗免疫马跟踪检测17个月,在接种3周后ELISA检测均呈阳性,其中一匹马ELISA抗体阳性持续到接种后10个月,另一匹马ELISA抗体阳性可持续到接种后一年.对两匹马的所有不同时期采集的血清样品经75℃加热5 min处理后,用ELISA检测均为阴性.另选6匹马传贫弱毒疫苗免疫马血清且ELISA检测抗体呈阳性的30个样品,经75℃加热5min处理后,均由阳性转变成阴性.4匹经马传贫病毒辽毒株(LN-EIAV)实验感染马且ELISA检测抗体呈阳性的血清样品,经75℃加热5 min处理后,结果仍为阳性.23匹ELISA检测抗体呈阳性的自然感染马血清样品,经加热处理后,19匹马血清样品仍为阳性,4匹马血清样品由阳性转变成阴性.结果表明弱毒疫苗免疫马较自然感染马血清抗体耐热性稍差.     

Effect of common head gear on horses]

The functions of the most common head-gears for horses are analysed from a biomechanical point of view. With the exception of the stable halter are all of them designed to enlarge the tensile forces transmitted through the reins or the longe, and to concentrate the enlarged forces on sensitive parts of the horse's head: the nose, or the lips, mandible and tongue. Since the direction, duration and size of these tensile forces are the essential factors to modulate signals for controlling the horse, a device has been developed to measure, or at least roughly quantify these forces. The mechanical characteristics of bosal, cave?on, serreta, kappzaum and hackamore are demonstrated and compared with those of the two major types of bits: those with and without levers.