Respiratory airflow patterns in ponies at rest and during exercise.

The exercise-induced changes in the equine breathing pattern were studied by analyzing tidal breathing flow-volume loops recorded in ten ponies both at rest and during a standardized exercise. Airflow, tidal volume, esophageal pressure and mask pressure were simultaneously recorded before, during and after a treadmill exercise. From the collected data, respiratory frequency and total pulmonary resistance were calculated, tidal breathing flow-volume loops were retraced using a computerized method and loop indices were measured for each period of the experimental protocol. For each pony, results of three consecutive daily measurements were averaged. The exercise loop indices were compared with the corresponding resting values using a one-way analysis of variance. The significantly changed indices were correlated with respiratory frequency and total pulmonary resistance. Several types of respiratory patterns were observed at rest as well as during exercise, although each pony was relatively constant in its own pattern of breathing. Most resting inspiratory and expiratory airflow curves were found to be biphasic. When ponies started running, the airflow developed an increasingly rectangular pattern. During strenuous exercise, both inspiratory and expiratory airflow curves showed a substantial increase of the volume acceleration and tended to a plateau. The loop indices relating the expiratory to the inspiratory airflow were significantly increased compared with their rest values. Correlations of these indices with respiratory frequency and total pulmonary resistance were weak.(ABSTRACT TRUNCATED AT 250 WORDS)     

The development of a radio-stethoscope for use in the horse at rest and during exercise

The development of a radio-stethoscope for horses is described. The equipment consisted of a sound transducer applied to the skin adjacent to the trachea and a radio transmitter attached to the saddle. The signals emitted were detected by telemetry and recorded on a magnetic tape-recorder. The recorder incorporated a monitor earphone so that sounds could be reproduced at the time of recording. The frequency response obtainable ranged from a few Hz to 4 KHz. This technique provided an objective means of studying the respiratory sounds generated during exercise although absolute values could not be measured.     

Frequency domain analysis of heart rate variability in horses at rest and during exercise

The pattern of variation in heart rate on a beat-to-beat basis contains information concerning sympathetic (SNS) and parasympathetic (PNS) contributions to autonomic nervous system (ANS) modulation of heart rate (HR). In the present study, heart period (RR interval) time series data were collected at rest and during 3 different treadmill exercise protocols from 6 Thoroughbred horses. Frequency and spectral power were determined in 3 frequency bands: very low (VLF) 0-< or = 0.01, low (LO) >0.01-< or = 0.07 and high (HI) >0.07-< or = 0.5 cycles/beat. Indicators of sympathetic (SNSI = LO/HI) and parasympathetic (PNSI = HI/TOTAL) activity were calculated. Power in all bands fell progressively with increasing exercise intensity from rest to trot. At the gallop VLF and LO power continued to fall but HI power rose. SNSI rose from rest to walk, then fell with increasing effort and was lowest at the gallop. PNSI fell from rest to walk, then rose and was highest at the gallop. Normalised HI power exceeded combined VLF and LO power at all gaits, with the ratio HI to LO power being lowest at the walk and highest at the gallop. ANS indicators showed considerable inter-horse variation, and varied less consistently than raw power with increasing physical effort. In the horses studied, the relationship between power and HR changed at exercise intensities associated with heart rates above approximately 120-130 beats/min. At this level, humoral and other non-neural mechanisms may become more important than autonomic modulation in influencing heart rate and heart rate variability (HRV). HRV at intense effort may be influenced by respiratory-gait entrainment, energetics of locomotion and work of breathing. HRV analysis in the frequency domain would appear to be of potential value as a noninvasive means of assessing autonomic modulation of heart rate at low exercise intensities, only. The technique may be a sensitive method for assessing exercise response to experimental manipulations and disease states.     

4个紫花苜蓿品种萌发期抗旱性比较

为对比甘肃广泛种植的4个紫花苜蓿品种(甘农1号、新疆大叶苜蓿、中苜1号和中天1号)萌发期的抗旱性,采用不同浓度聚乙二醇6000(Polyethylene glycol 6000,PEG-6000)模拟干旱胁迫的方法,测定4个紫花苜蓿品种的种子在干旱胁迫下的发芽势、发芽率、发芽指数、抗旱指数和根芽比,并用隶属函数法对4个紫花苜蓿品种的萌发期抗旱性进行综合评价.结果表明:4个紫花苜蓿品种的种子的发芽势、发芽率和发芽指数在各个PEG浓度下均为新疆大叶苜蓿最大,根芽比和抗旱指数为甘农1号最大;随胁迫程度的加剧4个紫花苜蓿品种的种子的发芽势、发芽率、发芽指数和抗旱指数均呈下降趋势,而根芽比先升高后降低:PEG浓度为5％ 时最大,分别为甘农1号6.91、新疆大叶苜蓿3.68、中苜1号4.54和中天1号6.04,0％ 时次之;与PEG浓度为0％ 时相比,PEG浓度为5％ 时,中天1号的发芽势和发芽指数下降幅度最大,PEG浓度为25％ 时,新疆大叶苜蓿的发芽率和中天1号的抗旱指数下降幅度最大.萌发期综合抗旱性为甘农1号>中苜1号>新疆大叶苜蓿>中天1号.     

Normal electrocardiographic QT interval in race-fit Standardbred horses at rest and its rate dependence during exercise

ObjectivesCardiac repolarization, measured as QT and T_peak to T_end (T_pT_e) intervals on the ECG, is important, as irregularities caused by diseases, ventricular hypertrophy, drugs and genetic defects can trigger arrhythmias which predispose human patients to syncope and sudden cardiac death. In horses, repolarization is not well described and therefore QT analysis cannot yet be used diagnostically. Therefore, we sought to describe reference values for the normal QT and T_pT_e intervals in Standardbreds and to determine the best method for heart rate (HR) correction.Animals30 Standardbreds.MethodsQT and T_pT_e intervals were measured during rest and exercise and plotted against HR converted to R_peak to R_peak interval (RR). Data were fitted with relevant regression models. Intra- and inter-observer agreement was assessed using Bland–Altman analyses.ResultsData were best described by a piecewise linear model (r² > 0.97). Average prediction error of this model was smaller than for both Bazett and Fridericia corrections. Coefficient of repeatability of intra- and inter-observer variability was 8.76 ms and 5.64 ms respectively and coefficient of variation was 1.77% and 2.76% respectively. T_pT_e increased with RR in stallions.ConclusionsThe QT interval in Standardbred horses shortens with decreasing RR interval (increasing HR) as in humans, but in a markedly different order as it clearly follows a piecewise linear model. The equine QT interval can be measured easily and there is small intra- and inter-observer variability. This model of the equine QT interval provides clinicians with a method that could support a diagnosis of repolarization disturbances in horses.     

Establishment of a multilevel linear model to analyse the factors affecting piglet litter performance at birth

This study aimed to establish a feasible model for analysing factors affecting piglet litter performance at birth. Data of 61,984 litters were collected from 16 herds, and general linear model (GLM), multilevel Poisson regression model (MPM) and multilevel linear model (MLM) were established to compare their goodness of fit for these data. Influencing factors of piglet litter performance at birth were analysed using the established optimal model. Results showed the intraclass correlation coefficients of total born piglets (TBP), piglets born alive (PBA), low-birth-weight piglets (LBW), and average birth weight of piglets (ABW) reached 27.89%, 23.88%, 24.66% and 22.27%, respectively (p < .05). Akaike's information criterion and Bayesian information criterion in MLM of TBP, PBA, LBW and ABW were lower than those in GLM. Pearson residuals in MPM increased to nearly 1 after introduction of a discrete scale factor, and the p values in MPM were similar to those in MLM. Analyses of MLM indicated crossbred sows with good management supplemented with oregano essential oil and farrowing at warm season had higher TBA, PBA and ABW, but lower LBW than other sows (p < .05). In conclusion, MLM is superior to GLM and can replace MPM in analysing discrete data with hierarchical structure in pig production. More importantly, other potential influencing factors of litter performance at birth can be analysed using the established MLM in the future.     

Effects of tension of the girth strap on respiratory system mechanics in horses at rest and during hyperpnea induced by administration of lobeline hydrochloride

OBJECTIVE: To determine whether tension of the girth strap of a saddle would sufficiently affect rib motion and reduce lung volume to alter pulmonary resistance in horses. ANIMALS: 10 healthy adult horses. PROCEDURE: We used classical techniques to measure the effects of tightening a girth strap (15 kg of tension) on pulmonary dynamics during eupnea and hyperpnea in horses. Respiratory impedance was evaluated by use of oscillometry, and resistance and reactance data were partitioned into lung and chest wall components. Rib cage and abdominal contributions to tidal volume and minute ventilation were measured by use of respiratory inductance plethysmography. Effects of strap tension on functional residual capacity (FRC) were measured during eupnea by use of a helium-dilution technique. In a subgroup of 6 horses, we also measured transdiaphragmatic pressures during eupnea and hyperpnea induced by administration of lobeline hydrochloride (0.2 mg/kg, i.v.). RESULTS: Pulmonary resistance measured by use of oscillometry but not by use of classical methods was significantly increased by the tension of the girth strap. However, the increase in pulmonary resistance could not be explained by a decrease in FRC. Motion of the rib cage was significantly reduced during eupnea and hyperpnea. However, ventilatory variables (tidal volume, minute ventilation, and peak flows), FRC, and transdiaphragmatic pressures were unaltered by strap tension. CONCLUSIONS AND CLINICAL RELEVANCE: Although tension of the girth strap caused measurable changes in respiratory mechanics (loss of rib motion and increased pulmonary resistance), there was no evidence that ventilation was limited.     

6种热带亚热带豆科牧草抗寒性及营养品质比较

为了筛选华南地区适宜的优质冬季青饲料草种,本研究比较了旋扭山绿豆(Desmodium intortum)、大叶山蚂蟥(Desmodium laxiflorum)、异果山绿豆(Desmodium heterocarpum)、显脉山绿豆(Desmodium reticulatum)、糙毛假地豆(Desmodium heterocarpum var.strigosum)和柱花草(Stylosanthes guianensis)6种热带亚热带豆科牧草在广州越冬期的抗寒性及营养品质。结果表明,除柱花草外,其它5种豆科牧草均能保持青绿越冬,其中旋扭山绿豆和大叶山蚂蟥的叶绿素含量均显著高于其它牧草(P0.05)。旋扭山绿豆的净光合速率最高(P0.05),其次是大叶山蚂蟥(P0.05),因此这两种牧草具有相对较强的抗寒性;与其它牧草相比,旋扭山绿豆在冬季能保持较高的粗蛋白含量(15.99%~20.26%)(P0.05)以及较低的洗涤纤维(NDF 27.92%~30.89%、ADF 23.96%~27.06%)和缩合单宁含量(6.05~11.95mg·g~(-1))(P0.05),因而具有较高的营养价值。因此,旋扭山绿豆可以作为华南地区冬季豆科青饲料的潜在优选草种。     

Pharmacokinetics of detomidine administered to horses at rest and after maximal exercise

Reason for performing study: Increased doses of detomidine are required to produce sedation in horses after maximal exercise compared to calm or resting horses. Objectives: To determine if the pharmacokinetics of detomidine in Thoroughbred horses are different when the drug is given during recuperation from a brief period of maximal exercise compared to administration at rest. Methods: Six Thoroughbred horses were preconditioned by exercising them on a treadmill. Each horse ran a simulated race at a treadmill speed that caused it to exercise at 120% of its maximal oxygen consumption. One minute after the end of exercise, horses were treated with detomidine. Each horse was treated with the same dose of detomidine on a second occasion a minimum of 14 days later while standing in a stocks. Samples of heparinised blood were obtained at various time points on both occasions. Plasma detomidine concentrations were determined by liquid chromatographymass spectrometry. The plasma concentration vs. time data were analysed by nonlinear regression analysis. Results: Median back‐extrapolated time zero plasma concentration was significantly lower and median plasma half‐life and median mean residence time were significantly longer when detomidine was administered after exercise compared to administration at rest. Median volume of distribution was significantly higher after exercise but median plasma clearance was not different between the 2 administrations. Conclusions and potential relevance: Detomidine i.v. is more widely distributed when administered to horses immediately after exercise compared to administration at rest resulting in lower peak plasma concentrations and a slower rate of elimination. The dose requirement to produce an equivalent effect may be higher in horses after exercise than in resting horses and less frequent subsequent doses may be required to produce a sustained effect.     

Heart rate variability and plasma norepinephrine concentration in diabetic dogs at rest

Cardiac autonomic neuropathy in dogs with diabetic mellitus (DM) was evaluated using measurement of heart rate variability (HRV) and plasma norepinephrine (NE) concentration. Dogs were divided into 2 groups; the control non-DM group (n?=?13) and the diabetic group (n?=?22) which was further divided into the well-controlled DM (n?=?11) and the poorly-controlled DM subgroups (n?=?11) according to their fasting plasma fructosamine concentrations. The electrocardiogram (ECG) was recorded continuously for at least 30?min to yield HRV. The results showed that in the poorly-controlled DM subgroup, the average of normal R-R interval (mean N-N), SD of the mean of all 5-min segments of normal RR intervals (SDANN) were lower than the control group while heart rate was higher (P?<?0.05). The NNA, SDNN, SDNN index and pNN50% were significantly lower when compared with the well-controlled DM subgroup (P?<?0.05). The high frequency (HF) and total power were significantly lower while the ratio of low to high frequency (LF/HF) was higher (P?<?0.05) when compared with the well-controlled DM subgroup. Moreover, in the poorly-controlled DM subgroup, plasma NE concentration was lower than the control group (210?±?37 vs. 479?±?74?pg/ml, P?<?0.05). There was a significantly negative correlation between plasma NE and plasma fructosamine concentrations. It is concluded that cardiac autonomic neuropathy occurred in poorly-controlled DM dogs. The sympathetic activity was suppressed as shown by decrease in both plasma NE concentration and LF component.     

Effects of exercise during the growing-finishing period on performance, age at puberty and conception rate of gilts

Littermate gilts were used to study the effects of exercise during the growing-finishing period on performance, age at puberty and conception rate. In trial 1, 12 gilts walked 15 min daily on a treadmill 6 d/wk (Monday through Saturday) until they attained body weights of about 100 kg, while 12 littermate gilts were not forced to exercise. Initial weight and age averaged 24.7 kg and 74 d, respectively. For trial 2, 12 gilts walked 30 min daily 6 d/wk (Monday through Saturday) on a treadmill, while 12 littermate gilts were not exercised. Initial weight and age of these gilts averaged 26.8 kg and 76 d, respectively. The treadmill was operated at 0 slope and at a speed of 2.6 km/h. Within trial, there were no differences (P greater than .05) in weight gain, average daily gain, feed consumed, feed to gain ratio, average backfat depth of loin eye area between gilts exercised and those not exercised. In both trials, there were no differences (P greater than .05) in age at puberty between exercised and nonexercised gilts. In trial 2, 10 gilts were selected in each of the exercised and nonexercised groups and were hand-mated to the same boar on the second estrous cycle. Eight gilts from the exercised group conceived, while nine from the nonexercised group conceived. Four gilts from the nonexercised groups had severe locomotor problems while only one gilt from the exercised groups had difficulty walking.     

Dynamic obstructions of the equine upper respiratory tract. Part 2: comparison of endoscopic findings at rest and during high-speed treadmill exercise of 600 Thoroughbred racehorses

REASONS FOR PERFORMING STUDY: The reliability of diagnoses of obstructive conditions of the upper respiratory tract (URT) based on examinations performed at rest vs. at exercise is controversial. OBJECTIVE: To compare diagnosis of URT by endoscopy at rest with that achieved during high-speed treadmill exercise (HSTE). HYPOTHESIS: Endoscopy of URT at rest, when performed in isolation from other simpler techniques is unreliable in the prediction of dynamic respiratory obstructions. METHODS: Endoscopic findings of 600 Thoroughbred racehorses during quiet breathing were compared with findings during high-speed treadmill exercise. Other parameters were also assessed for their specificity in diagnosis. RESULTS: Endoscopy of the resting horse showed low sensitivity (0.15) in the diagnosis of dorsal displacement of the soft palate (DDSP) and palatal instability (PI). When endoscopy and reported noises were taken together there was still a 35% misdiagnosis rate. Although there was significant association between resting laryngeal function score (LFS) and dynamic vocal cord and/or arytenoid cartilage collapse at exercise, 19% of horses with a grade 4/5 LFS were able to attain and maintain full abduction during exercise and 7% of those with 'normal' grades 1 or 2 LFS at rest showed dynamic laryngeal collapse when exerted. Sensitivity of the diagnostic model was greatly increased (80%) when a history of inspiratory noise and palpable intrinsic muscle atrophy were included. CONCLUSIONS AND POTENTIAL RELEVANCE: Endoscopy of the upper respiratory tract of static horses is unreliable in the diagnosis of dynamic obstructions of the URT and should not be used in isolation in surgical decision-making or in the assessment of horses at the time of sale.     

Comparison of bronchoalveolar lavage findings and measurements of gas exchange during exercise in horses with poor racing performance

Twenty-four Thoroughbred and twelve Standardbred racehorses aged between 2 and 6 years, presented for reported poor racing performance, underwent clinical exercise testing. During the last 10 s of exercise at each speed throughout an incremental speed exercise test on a treadmill inclined at a 10% slope, samples of arterial blood and expired gases were collected. Maximum oxygen uptake and the partial pressures of oxygen and carbon dioxide in arterial blood were determined. These values were compared between the two breeds of horses and also with reference to cytological findings of bronchoalveolar lavage samples, including neutrophil, erythrocyte and haemosiderophage percentage and the total nucleated cell concentration. The results revealed an inverse relationship (Spearman R = -0.45, p<0.05) between the total nucleated cell count in bronchoalveolar lavage samples and arterial oxygen partial pressure during exercise at 11 m.s^-1. This result suggests that subclinical pulmonary disease may be a more important cause of poor racing performance than previously thought. Also of note was a positive correlation (Spearman R = 0.50, p<0.05) between maximum oxygen untake and the percentage of erythrocytes.     

Comparison of bronchoalveolar lavage findings and measurements of gas exchange during exercise in horses with poor racing performance

Twenty-four Thoroughbred and twelve Standardbred racehorses aged between 2 and 6 years, presented for reported poor racing performance, underwent clinical exercise testing. During the last 10 s of exercise at each speed throughout an incremental speed exercise test on a treadmill inclined at a 10% slope, samples of arterial blood and expired gases were collected. Maximum oxygen uptake and the partial pressures of oxygen and carbon dioxide in arterial blood were determined. These values were compared between the two breeds of horses and also with reference to cytological findings of bronchoalveolar lavage samples, including neutrophil, erythrocyte and haemosiderophage percentage and the total nucleated cell concentration. The results revealed an inverse relationship (Spearman R = -0.45, p < 0.05) between the total nucleated cell count in bronchoalveolar lavage samples and arterial oxygen partial pressure during exercise at 11 m.s(-1). This result suggests that subclinical pulmonary disease may be a more important cause of poor racing performance than previously thought. Also of note was a positive correlation (Spearman R = 0.50, p < 0.05) between maximum oxygen uptake and the percentage of erythrocytes.     

14种景天属植物的抗旱性比较

在田间持续干旱胁迫条件下,通过比较14种景天属植物的表观形态、叶片相对含水量、丙二醛含量、叶绿素含量和可溶性糖含量等指标,分析其抗旱性。结果表明,乡巴佬景天（Sedum spectabile cv.Mossback）、八宝景天（S.spectaile Boreau）、何布景天（S.telephium cv.Herbstfreude）、冰山奇观景天（S.spectabile cv.Iceberg）和奇观景天（S.spectabile cv.Rosenteller）的抗旱性最强;詹姆士景天（S.spectabile cv.Jameson）、主妇景天（S.matrona）、粉红景天（S.spectabile cv.Rosebloom）、红景天（S.spectabile cv.Brilliant）、德国景天（S.hybridum）和粗壮景天（S.engleri）的抗旱性次之;反曲景天（S.reflexum）、胭脂红景天（S.spurium cv.Coccineum）和费菜（S.aizoon）的抗旱性最弱。     

Temporal and linear kinematics in elite and riding horses at the trot

Standard videography was used to determine the temporal and linear variables of 32 Spanish Purebreds at trot. Horses were organized into three groups: Group A (nonelite), comprising 13 stallions without any specific training program, which were hand led; Group B1 (elite), formed by 19 horses considered to be well-gaited and dressage trained, and which were also hand led; and Group B2 (ridden elite), comprising the same horses as the latter group but this time ridden. The horses ran at working trot, according to the trainers. Each animal was recorded using a Hi8 video camera. For temporal measurements, a 1/50 s time code was added to video images. Recordings were analyzed to provide times (seconds) at landing, mid-stance position, lift off and at subsequent landing in each limb. These data allowed the stride to be divided into its component phases by analysis of the variables for individual limbs, diagonal pairs and overall stride. The linear variables (meters) analyzed were stride length and overtracking, obtained for each stride from digitized images and calculated on a spreadsheet. Data were then compared between Groups A-B1 and Groups B1–B2.

Stride duration (0.639±0.064 vs 0.672±0.037 s) and stride length (247.7±21.9 vs 238.5±18.1 cm) of horses from A and B1 groups were similar; Group B1 was characterized by limb support and overlap values close to those of Group A; however, limb swing (forelimbs: 0.391±0.032 s; hind limbs: 0.374±0.027 s), diagonal swing (0.365±0.027 s) and inter-overlap (0.131±0.035) were of greater duration. Additionally, the proportion of horses with advanced placement was greater in Group B1.

Group B2 displayed greater stride duration (0.718± 0.054 s) and lower stride length (217.3±26.1 cm) than B1 group. The analysis revealed mounted horses to be characterized by limb and diagonal swings similar to those of Group B1; however, limb support and overlap were significantly greater, and inter-overlap and suspension phase were shorter.     

Parturition body size and body protein loss during lactation influence performance during lactation and ovarian function at weaning in first-parity sows

We investigated the effect of body protein mass at parturition and different degrees of body protein loss in lactation on sow performance. In a 2 x 2 factorial arrangement, 77 Genex gilts were fed to achieve either a standard or high body mass at parturition and to lose either a moderate (MPL) or high (HPL) amount of protein in lactation. Pregnant gilts were fed either 24.4 MJ of ME, 266 g of CP, and 11 g of lysine/d or 34.0 MJ of ME, 436 g of CP, and 20 g of lysine/d resulting in divergent (P < 0.01) live weights (165 vs. 193 kg) and calculated protein masses (24.3 vs. 30.0 kg) and slightly different backfat depths (20.0 vs. 22.8 mm; P < 0.05) at parturition. Diets fed during lactation were formulated to deliver 731 g of CP and 37 g of lysine/d or 416 g of CP and 22 g of lysine/d to induce differential body protein mobilization. Sows were slaughtered at weaning (d 26), and the weight of the organs and the lean, fat, and bone in five primal cuts was measured. The external diameter of the eight largest follicles on each ovary was recorded, and the follicular fluid from these follicles was collected, weighed, and analyzed for estradiol. Losses in lactational live weight (26 vs. 20 kg; P < 0.01) and calculated protein mass (17.8 vs. 10.7%; P < 0.001) were greater, and the carcass lean mass at weaning was 10% lighter (P < 0.05) in HPL sows. Backfat (5.1 +/- 0.8 mm; P = 0.29) and calculated fat mass (25.8 +/- 1.5%; P = 0.84) losses did not differ between treatments. Both sow body mass (P < 0.05) and lactation protein loss (P < 0.01) affected litter growth rate. Litter growth rate decreased (P < 0.05) at the end of lactation in HPL sows once these sows had lost 10 to 12% of their calculated protein mass. Ovarian follicular development was most advanced in high body mass sows that lost the least protein; these sows had the heaviest (P < 0.05) uterine weight and highest (P < 0.05) follicular fluid estradiol concentration. Follicular development was least advanced in standard body mass sows that lost the most protein. These sows had the lowest (P < 0.05) muscle:bone ratio at weaning and likely lost the largest proportion of their muscle mass compared with the other treatments. In conclusion, ovarian function at weaning and litter performance was higher in high body mass sows and in sows that lost the least protein in lactation, suggesting that a larger lean mass may delay the onset of a decrease in performance in sows that lose protein in lactation.