Tetsuro Hada

Assessment of autonomic nervous function by power spectral analysis of heart rate variability in the horse

We studied power spectral analysis of heart rate (HR) variability in the horse, with the hypothesis that the quantitative information provided by the spectral analysis of HR variability reflects the interaction between sympathetic and parasympathetic regulatory activities. For this purpose, electrocardiogram, blood pressure (BP) and respiratory (Resp) waveform were simultaneously recorded from Thoroughbred horses (3-5 years old) and analyzed by power spectrum. There were two major spectral components at low-frequency (LF) and high-frequency (HF) bands for HR variability. The peak of Resp variability clearly occurred at the HF range. In contrast to Resp variability, the power spectra of BP variability occurred at lower frequencies. The maximum coherence between HR and Resp variabilities and HR and BP variabilities occurred at approximately 0.15 and approximately 0.03 Hz, respectively. These relationships were similar to the ensemble spectra. On the basis of these data, we have defined two frequency bands of interest: LF (0.01-0.07 Hz) and HF (0.07-0.6 Hz). Therefore, we believe that power spectral analysis of HR variability provides a very powerful technique for assessing autonomic nervous activity in the horse.

Effects of Novelty Stress on Neuroendocrine Activities and Running Performance in Thoroughbred Horses

This study investigated the effects of novelty stress on neuroendocrine activities and running performance in Thoroughbred horses. First, to examine the neuroendocrine responses to novelty stress, we exposed horses to two types of novel environmental stimuli (audiovisual or novel field stimuli). After the stimuli, plasma concentrations of vasopressin, catecholamines and adrenocorticotropin (ACTH), as well as heart rates, were significantly increased in each experiment. Second, we investigated neuroendocrine activities during incremental exercise. Plasma concentrations of vasopressin, catecholamines, ACTH and blood lactate increased as the exercise load increased. Finally, we investigated the effects of novelty stimuli on neuroendocrine activities and running performance during supra‐maximal exercise (110% VHRmax). When the novelty stimuli were presented to horses, the increases in plasma vasopressin and catecholamines due to exercise load were significantly smaller than those in the control experiments. Blood lactate during supra‐maximal exercise was also significantly lower and total run time until exhaustion was prolonged in the novel environmental stimuli compared to the control. These results suggest that novelty stimuli facilitate vasopressin release from the posterior pituitary in addition to activating the sympatho‐adrenomedullary and the hypothalamic‐pituitary‐adrenocortical axes in thoroughbred horses, and increase exercise capacity, resulting in improvement of running performance during supra‐maximal exercise.

Effects of warm-up intensity on oxygen transport during supramaximal exercise in horses

OBJECTIVE To determine whether warm-up exercise at different intensities alters kinetics and total contribution of aerobic power to total metabolic power in subsequent supramaximal exercise in horses. ANIMALS 11 horses. PROCEDURES Horses ran at a sprint until fatigued at 115% of maximal oxygen consumption rate (VO(2max)), beginning at 10 minutes following each of 3 warm-up protocols: no warmup (NoWU), 1 minute at 70% VO(2max) (moderate-intensity warm-up [MoWU]), or 1 minute at 115% VO(2max) (high-intensity warm-up [HiWU]). Cardiopulmonary and blood gas variables were measured during exercise. RESULTS The VO(2) was significantly higher in HiWU and MoWU than in NoWU throughout the sprint exercise period. Blood lactate accumulation rate in the first 60 seconds was significantly lower in MoWU and HiWU than in NoWU. Specific cardiac output after 60 seconds of sprint exercise was not significantly different among the 3 protocols; however, the arterial mixed-venous oxygen concentration difference was significantly higher in HiWU than in NoWU primarily because of decreased mixed-venous saturation and tension. Run time to fatigue following MoWU was significantly greater than that with NoWU, and there was no difference in time to fatigue between MoWU and HiWU. CONCLUSIONS AND CLINICAL RELEVANCE HiWU and MoWU increased peak values for VO(2) and decreased blood lactate accumulation rate during the first minute of intense exercise, suggesting a greater use of aerobic than net anaerobic power during this period.

Quantitative evaluation of cervical cord compression by computed tomographic myelography in Thoroughbred foals

ABSTRACT Five Thoroughbred foals (age, 8–33 weeks; median age, 31 weeks; weight, 122–270 kg; median weight, 249 kg) exhibiting ataxia with suspected cervical myelopathy (n=4) and limb malformation (n=1) were subjected to computed tomographic (CT) myelography. The areas of the subarachnoid space and cervical cord were measured on transverse CT images. The area of the cervical cord was divided by the area of subarachnoid space, and stenosis ratios were quantitatively evaluated and compared on the basis of histopathological examination. The sites with a ratio above 52.8% could have been primary lesion sites in the histopathological examination, although one site with a ratio of 54.1% was not a primary lesion site. Therefore, in this study, a ratio between 52.8–54.1% was suggested to be borderline for physical compression that damages the cervical cord. All the cervical vertebrae could not be scanned in three of the five cases. Therefore, CT myelography is not a suitable method for locating the site of compression, but it should be used for quantitative evaluation of cervical stenosis diagnosed by conventional myelography. In conclusion, the stenosis ratios determined using CT myelography could be applicable for detecting primary lesion sites in the cervical cord.

A clinical case of equine fungal placentitis with reference to hormone profiles and ultrasonography.

ABSTRACT Fungal placentitis is an infectious disease inducing abortion in pregnant mares. In the present report, we describe a field case of abortion caused by fungal placentitis with consecutive examinations. The progesterone level and combined thickness of the uterus and placenta (CTUP) were abnormal before the onset of clinical signs. Additionally, the estradiol level started to change before the appearance of clinical signs. Abnormal serum amyloid A values and an abnormal fetal heart rate were observed after the onset of clinical signs. The present report demonstrates that the progesterone level and CTUP may be adequate as early diagnostic markers of fungal placentitis and bacterial infection. Endocrinological evaluation based on cutoff values or serial measurements were also useful for early diagnosis.

Effect of Myostatin SNP on muscle fiber properties in male Thoroughbred horses during training period

Variants of the Myostatin gene have been shown to have an influence on muscle hypertrophy phenotypes in a wide range of mammalian species. Recently, a Thoroughbred horse with a C-Allele at the g.66493737C/T single-nucleotide polymorphism (SNP) has been reported to be suited to short-distance racing. In this study, we examined the effect of the Myostatin SNP on muscle fiber properties in young Thoroughbred horses during a training period. To investigate the effect of the Myostatin SNP on muscle fiber before training, several mRNA expressions were relatively quantified in biopsy samples from the middle gluteal muscle of 27 untrained male Thoroughbred horses (1.5 years old) using real-time RT-PCR analysis. The remaining muscle samples were used for immunohistochemical analysis to determine the population and area of each fiber type. All measurements were revaluated in biopsy samples of the same horses after a 5-month period of conventional training. Although the expressions of Myostatin mRNA decreased in all SNP genotypes, a significant decrease was found in only the C/C genotype after training. While, expression of VEGFa, PGC1α, and SDHa mRNAs, which relate to the biogenesis of mitochondria and capillaries, was significantly higher (54–82%) in the T/T than the C/C genotypes after training. It is suggested that hypertrophy of muscle fiber is directly associated with a decrease in Myostatin mRNA expression in the C/C genotype, and that increased expressions of VEGFa, PGC1α, and SDHa in the T/T genotype might be indirectly caused by the Myostatin SNP.

Serum Anti-Müllerian Hormone Concentrations in Mares With Granulosa Cell Tumors Versus Other Ovarian Abnormalities

Abstract Recently, anti‐Müllerian hormone (AMH) has been reported as a useful diagnostic marker for equine granulosa cell tumors (GCTs). The aim of this study was to examine and compare serum AMH and immunoreactive (ir)‐inhibin concentrations in mares with ovarian abnormalities other than GCT compared to mares with known GCT in order to determine more useful diagnostic criteria. Mares with a possible GCT based upon history were subsequently classified into those with GCT confirmed by histopathology and mares with other abnormal ovaries (AO) without a GCT based on follow‐up fertility information. Median concentrations of AMH were 72.6 ng/mL (quartiles: 20.6–458.5 ng/mL) in GCT and 0.70 ng/mL (0.26–1.44 ng/mL) in AO mares, and median concentrations of ir‐inhibin were 2.36 ng/mL (1.65–3.79 ng/mL) in GCT versus 0.93 ng/mL (0.69–1.46 ng/mL) in AO mares. The cutoff values based on receiver operating characteristic (ROC) analysis were 4.70 ng/mL for AMH and 1.65 ng/mL for ir‐inhibin. These cutoff values were slightly higher than the traditional value based on the normal reference range. The sensitivity, specificity, accuracy, and area under the ROC curve of AMH were higher than those of ir‐inhibin. In conclusion, we demonstrated the diagnostic criterion of serum AMH concentration for equine GCT. Anti‐Müllerian hormone is a more useful marker for diagnosis of equine GCT than ir‐inhibin. HighlightsDiagnostic criteria of serum anti‐Müllerian hormone (AMH) and ir‐inhibin for granulosa cell tumors (GCTs) were demonstrated.About 83.3% of GCT and 44.4% of other abnormal ovaries presented polycystic appearances.The cutoff value of serum AMH concentration was 4.7 ng/mL.It was possible for AMH to increase in transient enlarged ovaries other than in GCT.The diagnostic accuracy of AMH was higher than that of ir‐inhibin.

Changes of lying behavior in Thoroughbred foals influenced by age, pasturing time, and weather conditions

ABSTRACT The lying behavior of Thoroughbred foals on breeding farms was continuously measured using triaxial accelerometers. Accelerometers were attached on the side of the hind limb cannon and under the halter of six foals to record triaxial angle data every 10 sec for a period of 24 hr. Lying behavior was divided into sternal lying and lateral lying based on head angle. Sampling was performed for two consecutive days each week until weaning. Sampling periods were divided into two periods on the basis of pasturing time: daytime pasturing (period A: 7-hr pasturing period, 2–60 days of age) and overnight pasturing (period B: 19-hr pasturing period, 32–152 days of age). Lying duration and frequency were longer and higher, respectively, in period A (44.6% of the time and 26.8 ± 7.4 times per day) than those in period B (27.7% of the time and 15.3 ± 4.2 times per day). In addition, foals spent more time laterally in period A (48.1% of total lying time) than in period B (38.9% of total lying time). Foals lie down longer in stalls than in pastures (Period A, 56.3 vs. 16.0%; Period B, 52.5 vs. 21.1%). Lateral lying was also longer in the stall than in the pasture. Lying duration and frequency changed with age in period A. Wet weather prevented lying behavior in the pasture. These results suggested that age, weather, and pasturing time affected the lying behavior of Thoroughbred foals under management at a breeding farm. Triaxial accelerometers may be useful for monitoring equine lying behavior.

Aborted fetal sizes of Thoroughbred horses in Hidaka, Japan, between 2005 and 2015

ABSTRACT The degree of fetal growth restriction has been unclear in equine reproduction. In this study, 2,195 fetuses from 2,137 abortions during 11 seasons were examined to determine the causes of abortion, and fetal size dimensions (crown rump length and body weight) were measured. In total, 900 cases (42.1%) of abortion were identified as caused by viral infection (215, 10.1%), bacterial infection (156, 7.3%), fungal infection (25, 1.2%), circulation failure (406, 19.0%), multiple causes (66, 3.1%), deformity (13, 0.6%), placental abnormality (12, 0.6%), and other causes (7, 0.3%). All viral infections originated from equine herpes virus. Of all abortions, 94.3% occurred between 181–360 days of pregnancy, and the gestational ages at abortion were different based on the causes. Fetal sizes in viral abortions were considerably larger than those due to other reasons. Compared with viral infection, the crown rump length size dimension of fetuses aborted from multiple and fungal infection was affected. In addition, bacterial infection, circulation failure, and unknown causes of abortions also contributed to growth restriction in terms of body weight. In conclusion, the present study showed details of equine abortion and the relationships between causes of abortion and fetal size. Most of the aborted fetuses showed restrictions in their growth. The manifestations of growth restriction were more related to weight than skeletal length.