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Alves JC, Santos A, Lavrador C, Carreira LM. Minimal Clinically Important Differences for a Weight Distribution Platform in Dogs with Osteoarthritis. Animals (Basel) 2023; 14:128. [PMID: 38200859 PMCID: PMC10778445 DOI: 10.3390/ani14010128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 12/22/2023] [Accepted: 12/28/2023] [Indexed: 01/12/2024] Open
Abstract
In this retrospective study to determine the optimal method of evaluating static weight-bearing distribution to assess response to treatment in dogs with osteoarthritis using a weight distribution platform, data from the Clinica Veterinária de Cães (Portuguese Republican National Guard) clinical records were extracted. At baseline and at 15 days post-treatment, follow-up data from 80 dogs treated for bilateral hip osteoarthritis were categorized based on an anchor question. Estimates of minimal clinically important differences were calculated with distribution-based and anchor-based methods for deviation from normal weight-bearing and a symmetry index (SI). For deviation, the anchor-based methods provided a range from -0.3 to -3.1, and the distribution-based methods from 0.16 to 0.29. For SI, the anchor-based methods provided a range from -10.0 to -23.9, and the distribution-based methods from 1.31 to 2.88. Receiver operator characteristic curves provided areas under the curve >0.7, indicating an acceptable cut-off point. We presented estimates of -1 for deviation and -10 for SI in dogs with OA. These estimates can be used for research and patient monitoring. Future studies should include OA from other joints and animals from a broader clinical context.
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Affiliation(s)
- J. C. Alves
- Divisão de Medicina Veterinária, Guarda Nacional Republicana (GNR), Rua Presidente Arriaga, 9, 1200-771 Lisbon, Portugal
- Faculty of Veterinary Medicine, Lusófona University, 1749-024 Lisbon, Portugal
- Centro de Ciência Animal e Veterinária, Lusófona University, 1749-024 Lisbon, Portugal
- MED—Mediterranean Institute for Agriculture, Environment and Development, Instituto de Investigação e Formação Avançada, Universidade de Évora, Pólo da Mitra, Ap. 94, 7006-554 Évora, Portugal
| | - Ana Santos
- Divisão de Medicina Veterinária, Guarda Nacional Republicana (GNR), Rua Presidente Arriaga, 9, 1200-771 Lisbon, Portugal
| | - Catarina Lavrador
- MED—Mediterranean Institute for Agriculture, Environment and Development, Instituto de Investigação e Formação Avançada, Universidade de Évora, Pólo da Mitra, Ap. 94, 7006-554 Évora, Portugal
| | - L. Miguel Carreira
- Faculty of Veterinary Medicine, University of Lisbon (FMV/ULisboa), 1300-477 Lisbon, Portugal
- Interdisciplinary Centre for Research in Animal Health (CIISA), University of Lisbon, (FMV/ULisboa), 1649-004 Lisbon, Portugal
- Anjos of Assis Veterinary Medicine Centre (CMVAA), 2830-077 Barreiro, Portugal
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Kapun A, Adrion F, Gallmann E. Evaluating the Activity of Pigs with Radio-Frequency Identification and Virtual Walking Distances. Animals (Basel) 2023; 13:3112. [PMID: 37835719 PMCID: PMC10571748 DOI: 10.3390/ani13193112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 09/28/2023] [Accepted: 09/29/2023] [Indexed: 10/15/2023] Open
Abstract
Monitoring the activity of animals can help with assessing their health status. We monitored the walking activity of fattening pigs using a UHF-RFID system. Four hundred fattening pigs with UHF-RFID ear tags were recorded by RFID antennas at the troughs, playing devices and drinkers during the fattening period. A minimum walking distance, or virtual walking distance, was determined for each pig per day by calculating the distances between two consecutive reading areas. This automatically calculated value was used as an activity measure and not only showed differences between the pigs but also between different fattening stages. The longer the fattening periods lasted, the less walking activity was detected. The virtual walking distance ranged between 281 m on average in the first fattening stage and about 141 m in the last fattening stage in a restricted environment. The findings are similar to other studies considering walking distances of fattening pigs, but are far less labor-intensive and time-consuming than direct observations.
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Affiliation(s)
- Anita Kapun
- Institute of Agricultural Engineering, University of Hohenheim, Garbenstraße 9, 70599 Stuttgart, Germany; (F.A.); (E.G.)
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Information Technologies for Welfare Monitoring in Pigs and Their Relation to Welfare Quality®. SUSTAINABILITY 2021. [DOI: 10.3390/su13020692] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The assessment of animal welfare on-farm is important to ensure that current welfare standards are followed. The current manual assessment proposed by Welfare Quality® (WQ), although being an essential tool, is only a point-estimate in time, is very time consuming to perform, only evaluates a subset of the animals, and is performed by the subjective human. Automation of the assessment through information technologies (ITs) could provide a continuous objective assessment in real-time on all animals. The aim of the current systematic review was to identify ITs developed for welfare monitoring within the pig production chain, evaluate the ITs developmental stage and evaluate how these ITs can be related to the WQ assessment protocol. The systematic literature search identified 101 publications investigating the development of ITs for welfare monitoring within the pig production chain. The systematic literature analysis revealed that the research field is still young with 97% being published within the last 20 years, and still growing with 63% being published between 2016 and mid-2020. In addition, most focus is still on the development of ITs (sensors) for the extraction and analysis of variables related to pig welfare; this being the first step in the development of a precision livestock farming system for welfare monitoring. The majority of the studies have used sensor technologies detached from the animals such as cameras and microphones, and most investigated animal biomarkers over environmental biomarkers with a clear focus on behavioural biomarkers over physiological biomarkers. ITs intended for many different welfare issues have been studied, although a high number of publications did not specify a welfare issue and instead studied a general biomarker such as activity, feeding behaviour and drinking behaviour. The ‘good feeding’ principle of the WQ assessment protocol was the best represented with ITs for real-time on-farm welfare assessment, while for the other principles only few of the included WQ measures are so far covered. No ITs have yet been developed for the ‘Comfort around resting’ and the ‘Good human-animal relationship’ criteria. Thus, the potential to develop ITs for welfare assessment within the pig production is high and much work is still needed to end up with a remote solution for welfare assessment on-farm and in real-time.
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Rifkin RE, Grzeskowiak RM, Mulon PY, Adair HS, Biris AS, Dhar M, Anderson DE. Use of a pressure-sensing walkway system for biometric assessment of gait characteristics in goats. PLoS One 2019; 14:e0223771. [PMID: 31618281 PMCID: PMC6795426 DOI: 10.1371/journal.pone.0223771] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Accepted: 09/29/2019] [Indexed: 01/19/2023] Open
Abstract
The purpose of this study was to quantitatively assess gait characteristics and weight-bearing forces during ambulation in goats free of lameness using a pressure-sensing walkway as a biometric tool for stride, gait, and force analysis. Forty-six non-lame adult goats ranging in age from 5 to 6 years, mixed-breeds, and with a mean body weight of 52 ± 7.1 kgs were used. Goats were trained to walk over a pressure-sensing walkway. Data for analysis was collected on 2 different days, 3 days apart. On each day, 2 to 5 walking passes, in the same direction, were captured for each goat. Data from 2 valid passes meeting the criteria for consistent walking gait on each day were averaged then used for analysis. Analysis was performed, including the day-effect, for stride, gait, and force characteristics. Of the 46 goats enrolled in the study, complete data sets were achieved in 33 (72%) goats. Gait biometrics were similar among the assessment days; therefore, all data was pooled for the purpose of characterizing data for individual limb and biometric parameter comparisons at the individual goat level. Statistical analysis revealed that no difference within the paired limbs, and that there were significant differences between the front limbs and hind limbs. Maximum force and maximum peak pressure were significantly greater for the front limbs as compared with the hind limbs (p < 0.001). Based on the results, gait and force characteristics can be consistently measured in goats using a pressure-sensing walkway during a consistent walking gait. Goats apply greater force to the forelimbs during the weight-bearing phase of stride as compared with the hind limbs. The use of objective assessment tools is expected to improve the ability of researchers and clinicians to monitor changes in weight bearing and gait and will contribute to improved animal welfare.
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Affiliation(s)
- Rebecca E. Rifkin
- Department of Large Animal Clinical Sciences, University of Tennessee College of Veterinary Medicine, Knoxville, Tennessee, United States of America
- * E-mail:
| | - Remigiusz M. Grzeskowiak
- Department of Large Animal Clinical Sciences, University of Tennessee College of Veterinary Medicine, Knoxville, Tennessee, United States of America
| | - Pierre-Yves Mulon
- Department of Large Animal Clinical Sciences, University of Tennessee College of Veterinary Medicine, Knoxville, Tennessee, United States of America
| | - H. Steve Adair
- Department of Large Animal Clinical Sciences, University of Tennessee College of Veterinary Medicine, Knoxville, Tennessee, United States of America
| | - Alexandru S. Biris
- Center for Integrative Nanotechnology Sciences, University of Arkansas at Little Rock, Little Rock, Arkansas, United States of America
| | - Madhu Dhar
- Department of Large Animal Clinical Sciences, University of Tennessee College of Veterinary Medicine, Knoxville, Tennessee, United States of America
| | - David E. Anderson
- Department of Large Animal Clinical Sciences, University of Tennessee College of Veterinary Medicine, Knoxville, Tennessee, United States of America
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A Monosodium Iodoacetate Osteoarthritis Lameness Model in Growing Pigs. Animals (Basel) 2019; 9:ani9070405. [PMID: 31266184 PMCID: PMC6680622 DOI: 10.3390/ani9070405] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 06/28/2019] [Accepted: 06/28/2019] [Indexed: 12/12/2022] Open
Abstract
Lameness is a common problem in pigs, causing welfare issues in affected pigs and economic losses for farmers. It is often caused by osteoarthrosis (OA) in its acute or chronic form. We assessed face and construct validity of a potential model for naturally-occurring OA and its progression to chronic OA. Such a model would allow the assessment of possible interventions. Monosodium-iodoacetate (MIA) or isotonic saline was deposited in the intercarpal joint of 20 growing pigs. Functional effects were assessed using subjective (visual lameness scoring) and objective (kinetic gait analysis) techniques at several timepoints. Structural effects were assessed by histopathology at 68 days. Eight out of 10 MIA treated animals had histopathological OA lesions confirmed in the target joint, while for all saline treated animals the target joint was judged to be normal. Pressure mat analysis revealed increased asymmetric weight bearing in these animals compared to the control group on day 3, 14, 28 and 56. Visual scoring only showed a difference between groups on day 1. MIA did not cause prolonged visible lameness, thus face validity for OA under field conditions was not entirely met. Since objective gait parameters showed decreased weightbearing as a behavioral expression of pain, it may be used as a general model for movement-induced pain in pigs.
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Gorissen BMC, Uilenreef JJ, Bergmann W, Meijer E, van Rietbergen B, van der Staay FJ, Weeren PRV, Wolschrijn CF. Effects of long-term use of the preferential COX-2 inhibitor meloxicam on growing pigs. Vet Rec 2017; 181:564. [PMID: 29066475 DOI: 10.1136/vr.104175] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 07/03/2017] [Accepted: 09/04/2017] [Indexed: 01/11/2023]
Abstract
Meloxicam, a preferential COX-2 inhibitor, is a commonly used NSAID in pigs. Besides having potential side effects on the gastrointestinal tract, this type of drug might potentially affect osteogenesis and chondrogenesis, processes relevant to growing pigs. Therefore, the effects of long-term meloxicam treatment on growing pigs were studied. Twelve piglets (n=6 receiving daily meloxicam 0.4 mg/kg orally from 48 until 110 days of age; n=6 receiving only applesauce (vehicle control)) were subjected to visual and objective gait analysis by pressure plate measurements at several time points. Following euthanasia a complete postmortem examination was performed and samples of the talus and distal tibia, including the distal physis, were collected. Trabecular bone microarchitecture was analysed by microCT scanning, bone stiffness by compression testing and growth plate morphology using light microscopy. Animals were not lame and gait patterns did not differ between the groups. Pathological examination revealed no lesions compatible with known side effects of NSAIDs. Trabecular bone microarchitecture and growth plate morphology did not differ between the two groups. The findings of this in vivo study reduce concerns regarding the long-term use of meloxicam in young, growing piglets.
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Affiliation(s)
- Ben M C Gorissen
- Department of Pathobiology, Anatomy and Physiology Division, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Joost J Uilenreef
- Department of Clinical Sciences of Companion Animals, Anaesthesiology Division, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Wilhelmina Bergmann
- Department of Pathobiology, Division of Pathology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Ellen Meijer
- Department of Farm Animal Health, Behaviour and Welfare Group, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Bert van Rietbergen
- Department of Biomedical Engineering, Orthopaedic Biomechanics Division, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Franz Josef van der Staay
- Department of Farm Animal Health, Behaviour and Welfare Group, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - P René van Weeren
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Claudia F Wolschrijn
- Department of Pathobiology, Anatomy and Physiology Division, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
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Ison SH, Clutton RE, Di Giminiani P, Rutherford KMD. A Review of Pain Assessment in Pigs. Front Vet Sci 2016; 3:108. [PMID: 27965968 PMCID: PMC5124671 DOI: 10.3389/fvets.2016.00108] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Accepted: 11/15/2016] [Indexed: 11/13/2022] Open
Abstract
There is a moral obligation to minimize pain in pigs used for human benefit. In livestock production, pigs experience pain caused by management procedures, e.g., castration and tail docking, injuries from fighting or poor housing conditions, “management diseases” like mastitis or streptococcal meningitis, and at parturition. Pigs used in biomedical research undergo procedures that are regarded as painful in humans, but do not receive similar levels of analgesia, and pet pigs also experience potentially painful conditions. In all contexts, accurate pain assessment is a prerequisite in (a) the estimation of the welfare consequences of noxious interventions and (b) the development of more effective pain mitigation strategies. This narrative review identifies the sources of pain in pigs, discusses the various assessment measures currently available, and proposes directions for future investigation.
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Affiliation(s)
- Sarah H Ison
- Animal Behaviour and Welfare, Animal and Veterinary Sciences, Scotland's Rural College (SRUC), Edinburgh, UK; Easter Bush Veterinary Centre, Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Midlothian, UK
| | - R Eddie Clutton
- Easter Bush Veterinary Centre, Royal (Dick) School of Veterinary Studies, The University of Edinburgh , Midlothian , UK
| | - Pierpaolo Di Giminiani
- Food and Rural Development, School of Agriculture, Newcastle University , Newcastle upon Tyne , UK
| | - Kenneth M D Rutherford
- Animal Behaviour and Welfare, Animal and Veterinary Sciences, Scotland's Rural College (SRUC) , Edinburgh , UK
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Gorissen BMC, Wolschrijn CF, Serra Bragança FM, Geerts AAJ, Leenders WOJL, Back W, van Weeren PR. The development of locomotor kinetics in the foal and the effect of osteochondrosis. Equine Vet J 2016; 49:467-474. [PMID: 27859501 PMCID: PMC5484372 DOI: 10.1111/evj.12649] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Accepted: 11/04/2016] [Indexed: 11/26/2022]
Abstract
Reason for performing study Foals stand and walk immediately after birth, but insight into the subsequent longitudinal development of their gait kinetics in the early juvenile phase and the possible influence of osteochondrosis thereon is lacking. Objectives To quantify gait kinetics in foals during the first half year of life, taking into account their osteochondrosis status. Study design Prospective, cohort study performed at a single stud farm. Methods Pressure plate measurements at walk and trot from 11 Dutch Warmblood foals during the first 24 weeks of life were used to determine body mass normalised peak vertical force, normalised vertical impulse and stance duration. Coefficients of variation of peak vertical force and stance duration were used as measures for gait maturity. Radiographs of tarsocrural and femoropatellar joints were taken at age 4–6 weeks and after 6 months to check for osteochondrosis. A linear mixed model was used to determine the effects of age, limb, presence of osteochondrosis and speed on gait parameters. Results Mean walking and trotting velocity increased over time as did stance duration and normalised vertical impulse, normalised peak vertical force values however remained relatively constant. During the first weeks of their life only the coefficient of variation of stance duration decreased significantly, while the coefficient of variation of peak vertical force did not. None of the foals was visibly lame, but the presence of osteochondrosis resulted in a temporarily but significantly reduced normalised peak vertical force. Main limitations This study is a relatively small sample size of one breed from a single stud farm. A stand‐alone pressure plate was used and body mass was estimated rather than measured. Conclusions Despite being precocious, foals need time to mature their gait. During growth, velocity at walk and trot increases, but normalised peak vertical force remains relatively constant. Although not visibly lame, a temporary reduction in normalised peak vertical force was detected in osteochondrosis positive foals using a pressure plate.
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Affiliation(s)
- B. M. C. Gorissen
- Department of Pathobiology, Anatomy and Physiology DivisionFaculty of Veterinary MedicineUtrecht UniversityUtrechtthe Netherlands
| | - C. F. Wolschrijn
- Department of Pathobiology, Anatomy and Physiology DivisionFaculty of Veterinary MedicineUtrecht UniversityUtrechtthe Netherlands
| | - F. M. Serra Bragança
- Department of Equine SciencesFaculty of Veterinary MedicineUtrecht UniversityUtrechtthe Netherlands
| | | | | | - W. Back
- Department of Equine SciencesFaculty of Veterinary MedicineUtrecht UniversityUtrechtthe Netherlands
- Department of Surgery and Anaesthesiology of Domestic AnimalsFaculty of Veterinary MedicineGhent UniversityMerelbekeBelgium
| | - P. R. van Weeren
- Department of Equine SciencesFaculty of Veterinary MedicineUtrecht UniversityUtrechtthe Netherlands
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Justolin PLT, Rahal SC, Agostinho FS, Mamprim MJ, Teixeira CR, Doiche DP, Babicsak VR. Radiographic and computed tomographic evaluation and gait analysis of Brazilian minipigs with syndactyly. Am J Vet Res 2016; 77:976-82. [PMID: 27580109 DOI: 10.2460/ajvr.77.9.976] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To characterize a population of Brazilian minipigs with naturally occurring syndactyly by use of plain radiographs and CT images and to evaluate kinetic and temporospatial variables by use of a pressure-sensing walkway. ANIMALS 10 Brazilian minipigs from 6 to 8 months of age (group 1, 5 healthy pigs [body weight, 10.5 to 18.5 kg]; group 2, 5 pigs with syndactyly [body weight, 7.5 to 18.0 kg]). PROCEDURES Forelimbs and hind limbs of all pigs were assessed by use of radiography and CT. Gait was analyzed by use of a pressure-sensing walkway. RESULTS All limbs of all pigs of group 2 had syndactyly. Two forelimbs had complex-1 syndactyly, and 8 forelimbs had complex-2 syndactyly. Four hind limbs had simple syndactyly, 1 hind limb had complex-1 syndactyly, and 5 hind limbs had complex-2 syndactyly. Kinetic and temporospatial values and symmetry indices did not differ between groups. Plantar and palmar surfaces of healthy pigs had 2 areas of maximum pressure, whereas plantar and palmar surfaces of pigs with syndactyly had only 1 area of maximum pressure. CONCLUSIONS AND CLINICAL RELEVANCE In this population of pigs, the most common type of syndactyly was complex-2, and comparison with the healthy group revealed no alteration in kinetic and temporospatial variables. Therefore, results suggested that syndactyly in young minipigs did not cause locomotor disturbances.
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Meijer E, van Nes A, Back W, van der Staay FJ. Clinical effects of buprenorphine on open field behaviour and gait symmetry in healthy and lame weaned piglets. Vet J 2015; 206:298-303. [PMID: 26521014 DOI: 10.1016/j.tvjl.2015.10.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Revised: 07/31/2015] [Accepted: 10/05/2015] [Indexed: 01/25/2023]
Abstract
Lameness in pigs decreases animal welfare and economic profit for the farmer. An important reason for impaired welfare in lame animals is pain due to lameness. No direct measurement of pain is possible in animals, and methods to indirectly detect and quantify the amount of pain an animal is experiencing are urgently needed. In this study, two methods to assess pain associated with lameness in pigs were evaluated to determine if they were sensitive enough to detect a lameness reduction as an effect of an experimental analgesic medication. Asymmetry associated with lameness was objectively quantified using pressure mat kinetic parameters: peak vertical force (PVF), load rate (LR), vertical impulse (VI) and peak vertical pressure (PVP). Locomotor activity was assessed in an open field test. A dose of 0.04 mg/kg buprenorphine, a strong analgesic, was used to treat 10 lame pigs, while eight other lame pigs, treated with physiological saline solution, served as controls. Buprenorphine decreased lameness-associated asymmetry for pressure mat LR (P = 0.002), VI (P = 0.003) and PVP (P = 0.001) and increased activity of the lame pigs in the open field (P = 0.023), while saline-treated animals did not show any changes in asymmetry and became less active in the open field (P <0.001). It was concluded that measurement of gait asymmetry by pressure mat analysis and locomotor activity in an open field test are both sensitive enough to detect the analgesic effects of buprenorphine when used to treat moderate to severe clinical pain in a relatively small group of affected pigs. The methods used in this study may also provide promising additional tools for future research into early pain recognition and lameness treatment in pigs.
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Affiliation(s)
- Ellen Meijer
- Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 7, NL-3584 CL Utrecht, The Netherlands.
| | - Arie van Nes
- Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 7, NL-3584 CL Utrecht, The Netherlands
| | - Willem Back
- Department of Surgery and Anaesthesiology, Faculty of Veterinary Medicine, Ghent University, B-9820 Merelbeke, Belgium; Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 112-114, NL-3584 CM Utrecht, The Netherlands
| | - Franz Josef van der Staay
- Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 7, NL-3584 CL Utrecht, The Netherlands
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