Polyurethane dressing, tetracycline and salicylic acid use for treatment of digital dermatitis in cattle. A comparative study.

OBJECTIVE: The use of antibiotics is a proven approach for local and systemic treatment of digital dermatitis (DD). Even if they are administered only locally and at low dosage, their use should be restricted to an absolute minimum. The efficacy of a commercial polyurethane wound dressing in treating acute digital dermatitis was compared with topical treatment using a commercially available tetracycline spray and a salicylic acid paste. MATERIALS AND METHODS: A total of 105 cows in a dairy farm (with about 160 dairy cows) were included in the study, with 101 cows needing topical treatment for digital dermatitis on one or both hind feet. All animals underwent hoof trimming prior to the treatment. Affected feet (n = 152) were randomly assigned to one of three comparable treatment groups. Topical treatment was administered to all visible digital dermatitis lesions. Animals in the positive control groups were given a topical treatment of tetracycline (53 DD lesions in 49 cows) or salicylic acid (53 DD lesions in 50 cows) formulations, whose therapeutic effects were scientifically verified. Spray was applied once, at a usual dosage and without any bandage. Salicylic acid paste was fixed in place with a bandage for 5 days. In the test group (46 DD lesions in 45 cows), a polyurethane bandage was left in place for 10 days. Whereas, 47 feet (from 38 cows) without lesions or with lesions showing no pain were designated as group 0. Each lesion was evaluated at day 0 during trimming, and on day 10 and 36. The lesions were scored based on severity and size. RESULTS: All groups showed a statistically significant improvement in the clinical appearance of the lesions at day 10. There were no significant differences in the findings between the second and the third evaluation (day 10 and day 36) either within a group or between the groups. CONCLUSION: The use of an alternative treatment regimen like a polyurethane wound dressing shows good clinical healing, it is as effective as the conventional methods, and unlike the conventional methods, does not require a latency period.

Quantitative assessment of the equine hoof using digital radiography and magnetic resonance imaging.

REASONS FOR PERFORMING STUDY: Evaluation of laminitis cases relies on radiographic measurements of the equine foot. Reference values have not been established for all layers of the foot. OBJECTIVES: To establish normal hoof wall and sole measurements using digital radiography (DR) and magnetic resonance imaging (MRI) and to document tissue components present in the dorsal hoof wall and solar layers seen on DR. STUDY DESIGN: Prospective observational case-control study. METHODS: Digital radiography and MRI were performed on 50 cadaver front feet from 25 horses subjected to euthanasia for nonlameness-related reasons. Four observers measured hoof wall (dorsal, lateral and medial) and sole thickness (sagittal, lateral and medial) using DR and magnetic resonance images. One observer repeated the measurements 3 times. Inter- and intraobserver correlation was assessed. RESULTS: Digital radiography and MRI measurements for the normal hoof wall and sole were established. Inter- and intraobserver pairwise Pearson's correlation for DR (r>0.98) and MRI measurements (r>0.99) was excellent. Based on MRI, the less radiopaque layer on DR is comprised of the stratum lamellatum and stratum reticulare. CONCLUSIONS: Normal DR and MRI measurements for the hoof wall and sole were established. On DR images, the less radiopaque layer of the foot observed corresponds to the critical tissues injured in laminitis, the strata lamellatum and reticulare. These reference measurements may be used by the clinician to detect soft-tissue changes in the laminitic equine foot and provide a foundation for future research determining changes in these measurements in horses with laminitis.

[Influence of a new biocidal product on the prevalence of digital dermatitis in dairy cows]. / Einfluss eines neuartigen Biozids auf die Prävalenz von Dermatitis digitalis bei Milchkühen.

OBJECTIVE: It was investigated whether usage of the biocidal product T-Hexx Dragonhyde (Hydromer, Branchburg, NJ, USA) could influence the prevalence of digital dermatitis (DD). MATERIAL AND METHODS: On a dairy farm (110 milking cows) 48 dairy cows without lameness were selected randomly for a test group or a control (negative) group, respectively. A high prevalence of DD (70-80%) was documented over a period of 2 months, during which four examinations were made, with an interval of 16-21 days between each examination. The respective grade of the DD-lesion on the hind hoofs was documented according to a scoring scheme. After precleaning the claws with water, the test group passed through a hoof bath containing T-Hexx Dragonhyde on 2 days per week at two milking times on each day, whereas the claws of control animals were cleaned using only a water bath. Splashes contaminating the animals and the environment were documented photographically and evaluated. Bacteriological examinations of the water bath and the T-Hexx-bath were performed after increasing numbers of animals had passed through the baths. RESULTS: Between and within groups no statistically significant differences in the prevalence of DD were found. DD-lesion scoring did not show any difference between the groups. With increasing numbers of animals having passed through the water bath, there was a significant increase in colony-forming units per millilitre and of enterobacteriaceae. In the T-Hexx Dragonhyde footbath, bacterial contamination remained below the detection limit at all times. The coloured splashes of the footbath were visible up to the level of the udder and teats. CONCLUSION AND CLINICAL RELEVANCE: The prevalence of DD was not influenced by the 2% or 4% concentration of the biocidal product in the footbath. Thus the microbiocidal effect of the solution did not lead to an efficient reduction in bacteria on the hoof. To demonstrate a potential preventive effect on DD, future studies would require herds with lower prevalence and a higher sample size. However, when applying footbaths there is the general risk of milk contamination or causing mastitis.

[Evaluation of a claw hygiene system concerning its cleaning effect, the cow traffic and the quality of the washing water]. / Einsatz einer Klauenwaschanlage unter Beurteilung der Reinigungswirkung, des Tierverhaltens und der Waschwasserqualität.

OBJECTIVE: Only limited scientific information on the efficiency of claw cleaning systems for dairy cows is currently available. For this reason, this investigation aimed to test the devio AG's claw hygiene system regarding its cleaning effect as well as its impact on the cow traffic and the quality of its washing water. MATERIAL AND METHODS: During the first of two investigative phases of this controlled study, main water was used to clean the claws, while in the second phase a biozide was additionally applied. Every 4 weeks the hind claws of approximately 55 dairy cows (German Fleckvieh breed) were evaluated and their degree of soiling classified into four categories. In addition to the system's cleaning effect, its effect on cow traffic was investigated using video recordings and the quality of the recycled washing water was tested using bacteriological sampling. RESULTS: In the second investigation phase, claw cleanliness in the treatment group was significantly higher than in the control group. However, there was no significant difference between the two groups during the first investigation phase. The video analysis showed, that after a short period of adaptation, there was undisturbed cow traffic. Within one week of installing the claw hygiene system, the length of stay in the system increased from a mean of 23 s to 32 s and the time the cows spent waiting in front of the system was reduced from a mean of 3 min 51 s to 2 min 20 s. Water analysis revealed an increasing bacterial count from initially 1.2 × 106 to 7.3 × 107 CFU/ml. CONCLUSIONS: The undisturbed cow traffic allows the easy integration of the claw cleaning system into a free-stall barn. The improvement of claw cleanliness can make a positive contribution to claw hygiene. However, the increasing bacterial contamination of the washing water gives cause for concern in terms of infections being passed between cows when using this system.

Finite element analysis of the ovine hip: development, results and comparison with the human hip.

OBJECTIVES: The ovine hip is often used as an experimental research model to simulate the human hip. However, little is known about the contact pressures on the femoral and acetabular cartilage in the ovine hip, and if those are representative for the human hip. METHODS: A model of the ovine hip, including the pelvis, femur, acetabular cartilage, femoral cartilage and ligamentum transversum, was built using computed tomography and micro-computed tomography. Using the finite element method, the peak forces were analysed during simulated walking. RESULTS: The evaluation revealed that the contact pressure distribution on the femoral cartilage is horseshoe-shaped and reaches a maximum value of approximately 6 MPa. The maximum contact pressure is located on the dorsal acetabular side and is predominantly aligned in the cranial-to-caudal direction. The surface stresses acting on the pelvic bone reach an average value of approximately 2 MPa. CONCLUSIONS: The contact pressure distribution, magnitude, and the mean surface stress in the ovine hip are similar to those described in the current literature for the human hip. This suggests that in terms of load distribution, the ovine hip is well suited for the preclinical testing of medical devices designed for the human hip.

Cartilage thickness and split-line pattern at the canine humeral trochlea.

OBJECTIVE: To characterise the humeral trochlea in middle to large breed dogs in respect to split-line pattern and cartilage thickness. METHODS: In 15 paired cadaveric elbow joints of mature dogs (>20 kg body weight) collagen network orientation of the hyaline cartilage of the humeral trochlea was visualised using a traditional split-line technique in which a dissecting needle dipped in India ink was inserted into the cartilage (n = 10). Cartilage thickness was measured radiographically on osteochondral plugs harvested at four representative locations within the joint surface of the humeral trochlea (n = 15). RESULTS: The joint surface of the humeral trochlea showed a distinct pattern of centripetally oriented split-lines with less pronounced or even absent split-lines caudo- proximally towards the olecranon fossa. Median cartilage thickness at the canine humeral trochlea was 0.51 mm (interquartile range: 0.42 - 0.61 mm). Centrally, at the region where osteochondrosis lesions commonly occur in middle to large breed dogs, the median cartilage thickness was 0.55 mm (interquartile range: 0.48 - 0.62 mm). CLINICAL SIGNIFICANCE: When focusing on anatomical joint resurfacing while performing osteochondral transplantation at the canine humeral trochlea, transplants should be implanted such that their split-lines are oriented centripetally. Hyaline cartilage thickness of transferred grafts should be in the range of half a millimetre to optimally match the situation at the canine humeral trochlea.

[Anatomical and pathophysiological features and treatment of elbow luxation in rabbits]. / Untersuchungen zur Anatomie, Pathophysiologie und Therapie der Luxatio antebrachii beim Kaninchen.

OBJECTIVE: Functional anatomical evaluation of elbow luxation in rabbits and the comparison of this lesion to cats and dogs. MATERIAL AND METHODS: The relative frequency of elbow luxation and the most common direction of antebrachial bone dislocation in rabbits were compared catamnestically with data in dogs and cats. Goniometric evaluation of the range of motion of the elbow was carried out in 14 rabbits. This was followed by visualisation of the anatomical structures of cadaver elbows and measurement of the subchondral bone density of the elbow using computed tomographic osteoabsorptiometry in seven rabbits and seven cats. Finally, the stabilisation of the elbow joint using wire to replace the collateral ligaments was evaluated in cadaver specimens. RESULTS: Rabbits undergo elbow luxation approximately four times more often than cats and dogs when compared to luxation of the hip joint. Caudal elbow luxation is most commonly seen in rabbits. The elbow functions as a "snap joint" because of the eccentric insertion of the collateral ligaments and has good lateral stability, which is afforded by a sagittal crest of the humeral condyle. Computed tomographic osteoabsorptiometry showed that the caudal region of the elbow joint undergoes the most mechanical stress. CONCLUSIONS AND CLINICAL RELEVANCE: The anatomical structure of the elbow of rabbits allows primarily sagittal movement; excessive force poses a risk of injury to the cranial aspect of the joint capsule and the humeroulnar ligaments. When closed reduction and a Velpeau sling do not provide stabilisation for the treatment of elbow luxation, transosseus replacement of the humeroulnar collateral ligaments may be indicated.

Functional anatomy of the distal radioulnar ligament in dogs.

The objective of this study was to functionally characterize the distal radioulnar ligament connecting the distal ends of canine antebrachial bones. The ligament has been investigated histologically in five adult dogs. After decalcification and standard paraffin embedding, 5-microm-thick sections have been stained with Hematoxylin/Eosin, Resorcin/Fuchsin, Astrablue/Nuclear-fast-red, Astrablue/Orange G. The distal radioulnar ligament can be divided into two parts, a proximal, 'interosseous' and a distal 'articular'. The former as a connecting structure experiences almost exclusively tensile stress in a proximolateral direction. The latter with an additional meniscal function is loaded in a combined tensile and compressive way. These findings can be explained with the characteristic valgus conformation of the canine carpal joint.

A method of biomechanical testing the suspensory apparatus of the third phalanx in cattle: a technical note.

There are a number of differences between the claws of the front and hind limbs in cattle concerning macroscopic shape, chemical and physical properties of claw horn and epidemiological data. Front claws have superior data in almost every respect. Virtually no information is available on the mechanical stability of the suspensory apparatus of the third phalanx. It was the objective of this study to develop a method to measure the maximum strength (N/mm2) of the suspensory apparatus of the bovine distal phalanx. This apparatus includes all layers of tissue such as bone, corium, corioepidermal junction and wall horn. The feet of 13 clinically healthy beef bulls were collected from the local abattoir. Testing was performed in three locations of the wall segment (dorsal, abaxial, axial) in a material testing machine. The corium and the corioepidermal junction were set under increasing tension until failure occurred. Maximum stress was recorded. The values ranged between 2.47-3.13 N/mm2 (dorsal), 4.08-4.87 N/mm2 (abaxial) and 2.27-2.66 N/mm2 (axial). No differences could be validated statistically between front and hind claws and between lateral and medial claws respectively. Abaxial ultimate stress values were significantly higher than dorsal and axial ones. Between the two a statistical difference could not be validated. Most of the specimens (57.1%) were torn apart at the corioepidermal junction, almost a quarter of the samples (27.6%) were to a degree disrupted at the corioepidermal junction and to a certain extent in the deeper layers of the corium. A few samples showed disruption within the horn (11.5%) or at the attachment of the third phalanx (3.8%). Biomechanical features of the experimental set-up are discussed. The biological significance of these findings is that the body weight and the additional dynamic loading is predominantly taken over by the abaxial part of the claw, while the dorsal and axial aspects are less loaded.

Comparison of radiography and scintigraphy in the diagnosis of dental disorders in the horse.

Scintigraphy, with 99mTechnetium methylenediphosphonate (99mTc-MDP) and 99mTc-labelled leucocytes, was compared to radiography in the diagnosis of dental disease in the horse in a prospective case-controlled study, comprising 30 horses with clinical signs of dental disease and 30 control horses. In each case, right and left lateral, ventral and dorsal soft tissue and bone phase scintigraphic images were obtained after i.v. injection of 1 GBq/100 kg bwt 99mTc-MDP, using a gamma camera. The same views were acquired in 10 horses with clinical signs of dental disease and 12 control horses after injection of 99mTc-labelled leucocytes. Standard radiographic projections of the paranasal sinuses and of the apices of the maxillary and mandibular teeth were obtained. The scintigraphs and radiographs were assessed subjectively by 2 board-certified surgeons and one board-certified radiologist, with extensive experience of equine radiology, from who the clinical history was withheld. Sensitivity, specificity and kappa, as a measure of agreement, were calculated for the different methods. Bone phase images were also scored subjectively on a scale from 0 to 3 on the basis of isotope uptake over the teeth. Regions of interest were defined over the teeth, and normal teeth compared to diseased counterparts. Total scintigraphic counts were related to the age of the animal and to the disease process. Differences in density ratios between left and right teeth were evaluated using the Mann-Whitney Test. Dental disease was confirmed in 22 horses at surgery or postmortem examination. Horses with dental disease showed a significant increase in scintigraphic activity over the affected tooth compared to the contralateral tooth, with a typical pattern for different diseases. The sensitivity of scintigraphy with 99mTc-MDP proved to be excellent (95.5%), whereas the specificity was moderate (86.4%). In contrast, radiography had excellent specificity (95.0%) and a low sensitivity (51.5%). The greatest sensitivity and specificity were achieved by evaluating radiographs and scintigrams together. The objective scintigraphic density ratios were found to be significantly different between diseased and control horses. The results of this study suggest that, if a density ratio of 1.5 or greater between a suspected diseased tooth and its contralateral number is regarded as abnormal, only 1% false positive diagnoses and 20% false negative diagnoses will occur. In contrast, scintigraphy with 99mTc-labelled leucocytes was not very successful, due to the lack of anatomical detail provided by this technique, which made identification of the diseased tooth impossible. Accurate radiographic interpretation of dental disease presents difficulties, both in terms of missed diagnoses and mistaken diagnoses. Scintigraphy complements radiographic examination of dental structures by providing information important for accurate diagnosis and is, therefore, conceived to be essential for selection of the appropriate treatment for dental disease.

Transrectal Doppler sonography of uterine blood flow.

Transrectal Doppler ultrasound was used for the noninvasive investigation of uterine blood flow in cows. Both the left and right Aa. uterinae were scanned to obtain blood flow velocity waveforms over 2 consecutive estrous cycles. Blood flow was reflected by the resistance index (RI) and the time-averaged maximum velocity (TAMV). Intra-observer reproducibility of Doppler measurements was evaluated. The intra-class correlation coefficient (Intra-CC) was 0.97 for the RI and 0.95 for TAMV. While RI values did not differ between the left and right A. uterina (P > 0.05), differences in TAMV occurred between both vessels in 2 cows. These differences were not related to the ovary bearing the dominant follicle or to the corpus luteum (P < 0.001). As in all cows, changes of RI and TAMV values between the left and right artery during the estrous cycle were correlated (correlation coefficient r > 0.72; P < 0.0001); the mean values of both sides were used for subsequent analyses. Variance component estimates for the effect of cow on RI and TAMV were 8 and 13% and for the influence of day of estrous cycle they were 70 and 47%, respectively (P <0.0001). Between estrous cycles no significant differences could be measured within cows (P > 0.05). The highest RI and lowest TAMV values occurred on Day 0 (= day of ovulation) and Day 1, while the lowest RI and highest TAMV values were measured between Days -3 and -1 of the estrous cycle, respectively. There was a positive correlation between TAMV and estrogen concentrations and a negative correlation between RI and plasma estrogen levels. Plasma progesterone levels and TAMV were negatively correlated, but no correlation could be measured (P > 0.05) between RI values and plasma progesterone concentrations. While there were no differences in plasma concentrations of estrogens and progesterone between estrous cycles within cows, the levels of these hormones differed between cows. The results show that transrectal Doppler sonography is a useful, noninvasive method for examining uterine blood flows in cows. If there is an influence of uterine perfusion on fertility in cows its role needs further investigation.

The visible animal project: a three-dimensional, digital database for high quality three-dimensional reconstructions.

The "Visible Animal Project" (VAP) is comprised of axial anatomic cryosections and corresponding CT and MR images of a mature dog. The digital database is used for the creation of three-dimensional computer graphics of canine anatomy. The technique of cryodissection is described in detail. The combining of the corresponding CT and MR images, and cryosections as well as the data processing for the creation of three-dimensional reconstructions is presented and examples are shown. For the first time a complete high-resolution three-dimensional database of a dog is available, which can be used as the base for further high quality three-dimensional reconstructions, similar to the "Visible Human Project" (VHP).

Macroscopic cryosectioning: a simple new method for producing digital, three-dimensional databases in veterinary anatomy.

Using a new method derived from the 'visible human project' (Spitzer et al., 1996, Journal of the American Medical Informatics Association, 3, 118-130), we were able to establish a simple and low-cost tool which produces high-quality cryosections of macroscopic specimens down to 1-mm slice thickness, based on a milling process. For the first time, a macroscopic cryotome is available to veterinary anatomists, which can be used on cutting faces up to 25 cm high and 50 cm wide and with a minimal slice thickness of 1 mm without any gap. The method employs a modified wood circular saw. Recording of the cutting faces is carried out 'online' by a high-resolution digital camera. The process has been tested extensively and produces high-quality sections of very hard material (teeth) as well as of very soft tissues (brain). It is now possible in veterinary medicine to provide three-dimensional anatomical databases of high resolution and of tissue-specific colour as an additional tool for high-quality two- and three-dimensional anatomical reconstructions for use in science and education.

[Liver fluke infestation in New World camelids. Parasitology, pathology, clinical findings and therapy]. / Leberegelbefall bei Neuweltkameliden. Parasitologie, Pathologie, Klinik und Therapie.

In Llamas and Alpacas infestation with Fasciola hepatica or Dicrocoelium dendriticum can cause liver damage, sometimes even with lethal outcome. Once infected South American Camelids (SACs) react more sensitively to these parasites than other domestic ruminants. We report here on the pathology, parasitology, clinics and therapy of this disease. Concerning Dicrocoelium dendriticum we describe own clinical results and therapeutic outcome in addition to the pathological investigation. According to anatomic corrosion casts, the bile ducts of SACs show more similarity with the equine bile system than with the bile system of domestic ruminants.

[Radiologic description of the growth plates of the atlas and axis in foals]. / Röntgenologische Darstellung der Wachstumsfugen an Atlas und Axis beim Fohlen.

Fractures of the first two cervical vertebrae, atlas and axis, may occur in foals for different reasons, e.g. in cases of a fall, going head over heels or when being hit by a hoof. The tentative clinical diagnosis can be confirmed by x-raying the standing animal, with aid of computed tomography in the anaesthetized foal respectively. The growth plates however, and their time of closure have to be considered when interpreting radiographs. In the atlas there are two ventrolateral plates and one dorsomedian cartilagineous plate. Only the dorsal plate, however, can be found in the dorsoventral projection up to an age of about 12 months. The ventrolateral growth plates which have closed at about six months of age cannot be seen in either ther dorsoventral or laterolateral projection. In transversely oriented CT-scans all of the three centres of ossification can easily be made visible in the atlas. In the axis the cartilagineous gaps between the dens axis and the cranial epiphysis as well as the cranial and caudal epiphyseal growth plate can be shown in normal x-radiographs in both planes of projection. Besides this there are growth plates between the corpus vertebrae and the arcus vertebrae in the axis which cannot be seen in either radiographic projection. They become clearly visible in transversal CT-scans and are ossified at the age of three to four months. At the end of the first year the growth plates between the dens axis and the cranial epiphysis have closed. The cranial and caudal epiphyseal plate are gone at an age of about four to five years.

A simplified assay for screening of drug resistance of cell-associated cytomegalovirus strains.

BACKGROUND: Conventional phenotypic drug resistance determination of cell-free clinical human cytomegalovirus (HCMV) isolates is usually very laborious and may take 8-12 weeks, since serially passages of slowly growing viral isolates in tissue cultures are required to obtain a sufficient viral titer for an appropriate inoculum. Rapid screening of a large number of samples would therefore only be possible if simplified, less work-intensive methods are employed. OBJECTIVE: The aim of this work was to develop an assay which speeds up the whole procedure of phenotypic drug resistance determination. Steps of the classical plaque reduction assay should be simplified or omitted, but on the other hand, the assay should be reliable and reproducible. STUDY DESIGN: Twenty-six clinical HCMV isolates from 20 immunocompromised patients (ten pre-treatment and 16 post-treatment with ganciclovir) were tested for drug susceptibility with the simplified plaque reduction assay. Most isolates were tested at least twice in independent assays. Virus titration could be avoided by using four different doses of cell-associated virus from the secondary culture for coculture susceptibility testing. Drug susceptibility values were determined by plaque titration and Probit analysis. RESULTS: All clinical HCMV isolates tested showed a mean ganciclovir ID50 value of 1.98 microM, (range 0.2-12.2; median 0.95) and a mean foscarnet ID50 value of 92.4 microM (range 35.7-181; median 81). All except one isolate were classified ganciclovir sensitive when compared to ID50 values of two ganciclovir resistant control stains (53.7 +/- 6.4 and 12.7 +/- 0.9 microM) and the sensitive laboratory strain Towne (2.1 +/- 0.8 microM). Repeated tests of individual isolates were reproducible, although the infectivity of the inoculum has not been determined prior of the assay. The mean time which elapsed between receipt of the clinical specimen and read-out of the assay was circa 4 weeks. CONCLUSIONS: Phenotypic resistance testing of HCMV isolates following to this protocol drastically reduces expenditure of time and work. The assay allows reliably the discrimination of HCMV isolates as drug resistant or sensitive according to the recent classification criteria of the AIDS Clinical Trials Group (ACTG). The simple handling and uncomplicated calibration of this assay facilitates the screening of large specimen numbers and renders drug susceptibility determination of HCMV more accessible to diagnostic routine use.

Investigations on the postnatal development of the macroscopic proportions and the topographic anatomy of the feline spinal cord.

The aim of this work was to investigate the postnatal development of the feline spinal cord. Our study showed that the main period of growth leading to the cervical and lumbar enlargements begins after birth and is completed at the age of 5-6 months. Comparing the relationship between the length of the spinal cord and the vertebral column, we found that in contrast to the adult cat, in the newborn cat, length, area and volume of segments show similar values along the spinal cord. This also applied to the length of the vertebrae. Due to a heterogeneous growth, not all segments of the spinal cord end up situated cranial to their corresponding vertebrae. As a consequence, the end of the conus medullaris is still located within the sacral canal in animals older than 2 months. These findings strongly propose that injection into the vertebral canal of the cat have to be performed caudal to the sacral vertebrae.

Transrectal color Doppler sonography of the A. uterina in cyclic mares.

Color Doppler ultrasound was used transrectally in 6 mares to locate both the left and right Aa. uterinae and to obtain flow velocity waveforms at defined times (Days 0, 5, 10, 15 and 20) during 4 estrous cycles. Blood flow reflected by the resistance index (RI) was determined for both arteries on 120 occasions. As there was no significant difference and a high correlation in the RI values between the left and right arteries (paired Student's t-test, correlation coefficient r > 0.94; P < 0.05), the average RI value was used for subsequent analyses. There were correlations between RI values, mares and day of estrous cycle (P < 0.0001). The mean RI was higher (P < 0.05) in the 2 multiparous mares (age, 12 to 13 yr) than in the 4 younger maiden mares (age, 6 to 10 yr). During the estrous cycle mean RI values on Day 0 (day of ovulation) and Day 10 were higher (P < 0.05) than on Days 5, 15 and 20, whereas between estrous cycles within mares no differences (P > 0.05) could be measured. The results suggest that transrectal Color Doppler sonography is a noninvasive method for examining differences in impedance to uterine blood flow between different mares and cycle periods.