Skin histology and its role in heat dissipation in three pinniped species

Background

Pinnipeds have a thick blubber layer and may have difficulty maintaining their body temperature during hot weather when on land. The skin is the main thermoregulatory conduit which emits excessive body heat.

Methods

Thorough evaluation of the skin histology in three pinniped species; the California sea lion-Zalophus californianus, the Pacific harbor seal-Phoca vitulina richardsi, and the Northern elephant seal-Mirounga angustirostris, was conducted to identify the presence, location and distribution of skin structures which contribute to thermoregulation. These structures included hair, adipose tissue, sweat glands, vasculature, and arteriovenous anastomoses (AVA). Thermal imaging was performed on live animals of the same species to correlate histological findings with thermal emission of the skin.

Results

The presence and distribution of skin structures directly relates to emissivity of the skin in all three species. Emissivity of skin in phocids (Pacific harbor and Northern elephant seals) follows a different pattern than skin in otariids (California sea lions). The flipper skin in phocids tends to be the most emissive region during hot weather and least emissive during cold weather. On the contrary in otariids, skin of the entire body has a tendency to be emissive during both hot and cold weather.

Conclusion

Heat dissipation of the skin directly relates to the presence and distribution of skin structures in all three species. Different skin thermal dissipation patterns were observed in phocid versus otariid seals. Observed thermal patterns can be used for proper understanding of optimum thermal needs of seals housed in research facilities, rescue centers and zoo exhibits.     

Use of infrared thermal imaging to diagnose health of Ammopiptanthus mongolicus in northwestern China

Population of the rare and endangered species Ammopiptanthus mongolicus (Maxim.) Cheng f. declined rapidly in China’s arid region and Central Asia. There is an urgent need to protect this species, whic...     

Induction of Noninflammatory Pain in an Experimental Foot Lameness Model in Horses

The mechanism by which nonsteroidal anti-inflammatory drugs mitigate pain caused by a heart bar shoe (HBS) model of lameness is unknown. The purpose of this study was to determine if this HBS model of lameness induces inflammation in horses. Five healthy adult horses from a university teaching herd were enrolled. A custom HBS was applied to the left front foot of each horse, followed by induction of the American Association of Equine Practitioners Lameness Score of 4. Inflammatory markers including serum amyloid A (SAA) concentration, local venous tumor necrosis factor alpha and prostaglandin E2 (PGE2) concentrations, and foot temperature were measured before lameness induction and 1, 3, and 13 hours after lameness induction. Lameness induction using the HBS model did not significantly increase production of plasma SAA, tumor necrosis factor alpha, or PGE2 concentrations at measured time points. Immediately and 1 hour after lameness induction, dorsal coronary band temperatures were higher in the left front foot compared with the right front foot, but there was no difference at 3 or 13 hours. In conclusion, the HBS model did not induce inflammation as assessed by select inflammatory markers, suggesting that the HBS model induces mechanical rather than inflammatory pain. This should be considered when using the HBS model to assess analgesic drugs in horses.     

Development and validation of an automatic thermal imaging process for assessing plant water status

Leaf temperature is a physiological trait that can be used for monitoring plant water status. Nowadays, by means of thermography, canopy temperature can be remotely determined. In this sense, it is crucial to automatically process the images. In the present work, a methodology for the automatic analysis of frontal images taken on individual trees was developed. The procedure can be used when cameras take at the same time thermal and visible scenes, so it is not necessary to reference the images. In this way, during the processing in batch, no operator participated. The procedure was developed by means of a non supervised classification of the visible image from which the presence of sky and soil could be detected. In case of existence, a mask was performed for the extraction of intermediate pixels to calculate canopy temperature by means of the thermal image. At the same time, sunlit and shady leaves could be detected and isolated. Thus, the procedure allowed to separately determine canopy temperature either of the more exposed part of the canopy or of the shaded portion. The methodology developed was validated using images taken in several regulated deficit irrigation trials in Persimmon and two citrus cultivars (Clementina de Nules and Navel Lane-Late). Overall, results indicated that similar canopy temperatures were calculated either by means of the automatic process or the manual procedure. The procedure developed allows to drastically reduce the time needed for image analysis also considering that no operator participation was required. This tool will facilitate further investigations in course for assessing the feasibility of thermography for detecting plant water status in woody perennial crops with discontinuous canopies. Preliminary results reported indicate that the type of crop evaluated has an important influence in the results obtained from thermographic imagery. Thus, in Persimmon trees there were good correlations between canopy temperature and plant water status while, in Clementina de Nules and Navel Lane-Late citrus cultivars canopy temperature differences among trees could not be related with tree-to-tree variations in plant water status.     

Assessing the Association Between Hoof Thermography and Hoof Doppler Ultrasonography for the Diagnosis of Lameness in Horses

The objectives of this study were to assess the correlation between hoof surface temperature and ultrasonographic measurements of digital blood vessels in horses and to evaluate the measurements' potential as predictors for clinical lameness. Twelve 3-year-old American Quarter Horses, 6 geldings and 6 mares, with average initial body weight of 459 ± 31 kg were used. On days 0, 30, 60, and 90 of the study, horses were weighed and subjected to clinical lameness examinations. Doppler ultrasonography was used to measure diameter of the medial palmar artery in the distal left forelimb and velocity of blood flow through that artery, starting at 60 minutes after morning feeding and repeated at 30-minute intervals. Temperature measurements on the hoof were collected at 15-minute intervals beginning 75 minutes after feeding, using a digital thermographic camera. A series of bivariate linear mixed models were fitted to estimate the correlation between Doppler and temperature measurements. The within-horse and between-horse correlations between hoof surface temperature and velocity of blood flow in the distal limb through the medial palmar artery was estimated at 0.40 (P > .50) and 0.99 (P < .001), respectively. These results indicate that at the horse level, the correlation between hoof temperature and velocity of blood flow in the distal limb was very high but that the within-horse correlation was not significantly different from 0. Velocity of blood flow at 60 minutes after feeding improved model fit to the lameness data, so it was included as a model predictor for lameness.     

Thermographic Evaluation of Racehorse Performance

The present study was aimed at identifying the key thermographic diagnostic areas essential for monitoring the effect of training on racehorses. The study involved monitoring 15 racehorses in 13 imaging sessions over a period of 10 months. Temperature measurements were made at a total of 46 regions of interest (ROIs) at the distal parts of the limbs and the back. To account for the influence of ambient temperature on each ROI measurement, values were adjusted to a constant ambient temperature of 12°C, estimated using regression analysis. The horses in the study were divided into two groups based on the value of success rate in racing competition. During the research period, none of the horses were identified as injured by routine veterinary investigation. Successful horses had significantly warmer adjusted ROI temperatures than their less successful counterparts at both carpal joints, the third metacarpal bones, the left fetlock joint, the left front short pastern bone, the left tarsus joint, and the caudal part of the thoracic vertebrae. The study tested a protocol for recording body surface temperature in racehorses, which was shown to increase reliability by adjusting for variations in ambient temperature. When analyzed on the basis of sporting performance, the protocol identified 14 ROIs that were associated with superior performance, most of which were at the limbs on the left side.     

Effects of Whole Body Vibration on the Horse: Actual Vibration,Muscle Activity,and Warm-up Effect

Whole body vibration (WBV) exercise has been introduced into human and recently also into equine training. Only a few studies about physical and physiological effects on horses are available. This study should clarify the actual physical vibration of a commercially available WBV plate itself and on the horse as well as the muscular activity in the limbs and back. Furthermore, the effects of WBV warm-up on clinical parameters and body surface temperatures were compared to standard warm-up exercises. Ten sound horses (vibration and muscle activity of six horses) were recorded while standing (control) and during 15 and 25 Hz (manufacturer information) vibration exercise. The vibration of plate, hoof, fetlock, withers, and sacrum was analyzed for frequency, peak-to-peak displacement, and peak acceleration. Activity of M. triceps, quadriceps, and longissimus dorsi was assessed using surface electromyography. Warm-up effects were compared between four different warm-up scenarios: standing (control), 10-minute vibration, 10-minute lunging (walk), and 12-minute lunging (walk and trot). Maximal body surface temperature of upper forelimb, thigh, and back was measured. Actual plate vibration frequency was 7 or 11 Hz with a maximum peak-to-peak displacement of 9 mm in longitudinal direction. WBV exercise induced no increase in electromyographic activity, clinical parameter, or body surface temperature. It was concluded that actual plate vibration was mainly longitudinal with a lower frequency than proposed and 10-minute exercise had no significant effect. Different vibration protocols and vibration acting in the vertical direction might enable more effective exercise in horses.