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Topic:Comparative Study

Comparative studies in equine research involve the systematic analysis of different horse breeds, management practices, or physiological responses to identify variations and similarities. These studies are instrumental in understanding how different factors influence health, performance, and behavior in horses. Common areas of comparison include genetic traits, nutritional requirements, disease resistance, and response to training. By evaluating these differences, researchers can develop targeted strategies for breeding, healthcare, and training. This page aggregates peer-reviewed research studies and scholarly articles that focus on the methodologies, findings, and implications of comparative studies in the context of equine science.
Comparison of conventional radiography and computed tomography as aids in the diagnosis of osteomyelitis in 11 foals.
Australian veterinary journal    June 27, 2018   Volume 96, Issue 7 257-261 doi: 10.1111/avj.12710
Lean NE, Perkins NR, Ahern BJ.Conventional radiography is currently the most common imaging modality used by veterinarians investigating foals with suspected osteomyelitis. Emerging evidence in adult horses and humans suggests computed tomography (CT) is a superior modality for evaluation of osseous changes in general. This study aimed to evaluate the potential benefits of CT versus conventional radiography in cases of osteomyelitis in foals. Methods: Cases of osteomyelitis in foals under 6 months of age admitted over a 6-year period at a single referral hospital that had both CT and conventional radiography images were ...
Evaluation of Histogel- and Gelfoam-embedded bronchoalveolar lavage and transtracheal wash fluids compared with cytocentrifuged and sediment smear preparations.
Veterinary clinical pathology    June 27, 2018   Volume 47, Issue 3 471-476 doi: 10.1111/vcp.12624
Haysom LZ, Lee-Fowler TM, Spangler EA.Storage and temperature significantly impact bronchoalveolar lavage fluid (BALF) analysis, and shipment of samples to diagnostic laboratories is often necessary. Alternative sample preparation methods could limit storage and temperature effects. Objective: This study aimed to determine if airway wash samples that were fixed in formalin after being embedded in Histogel or Gelfoam gave comparable results to fresh cytocentrifuged or sediment smear preparations for the evaluation of cell morphology. Methods: Eleven bronchoalveolar lavage and 3 transtracheal wash fluids were available, including 8 ...
Genome data uncover four synergistic key regulators for extremely small body size in horses.
BMC genomics    June 25, 2018   Volume 19, Issue 1 492 doi: 10.1186/s12864-018-4877-5
Metzger J, Rau J, Naccache F, Bas Conn L, Lindgren G, Distl O.Miniature size in horses represents an extreme reduction of withers height that originated after domestication. In some breeds, it is a highly desired trait representing a breed- or subtype-specific feature. The genomic changes that emerged due to strong-targeted selection towards this distinct type remain unclear. Results: Comparisons of whole-genome sequencing data from two Miniature Shetland ponies and one standard-sized Shetland pony, performed to elucidate genetic determinants for miniature size, revealed four synergistic variants, limiting withers height to 34.25 in. (87 cm). Runs of h...
Tumor necrosis factor-alpha protein concentrations in bronchoalveolar lavage fluid from healthy horses and horses with severe equine asthma.
Veterinary immunology and immunopathology    June 24, 2018   Volume 202 70-73 doi: 10.1016/j.vetimm.2018.06.014
Montgomery JB, Husulak ML, Kosolofski H, Dos Santos S, Burgess H, Meachem MD.The objective of this study was to determine if TNF-α protein concentration differs in bronchoalveolar lavage fluid (BALF) obtained from healthy horses, horses with naturally occurring exacerbations of severe equine asthma and horses in remission from severe equine asthma. Tumor necrosis factor-alpha (TNF- α) protein concentrations were determined in BALF by commercial equine ELISA. Horses with naturally occurring exacerbation of severe equine asthma were found to have significantly lower BALF TNF-α protein concentrations than healthy horses (p = 0.0026). There was no significant differ...
Cell specific microvesicles vary with season and disease predisposition in healthy and previously laminitic ponies.
Veterinary immunology and immunopathology    June 23, 2018   Volume 202 85-92 doi: 10.1016/j.vetimm.2018.06.001
Finding EJT, Lawson C, Elliott J, Harris PA, Menzies-Gow NJ.Microvesicles are small (up to 1 μm) vesicles found in plasma and other bodily fluids. They are recognised as part of the normal system of inter-cellular communication but altered numbers are also used as biomarkers of disease. Microvesicles have not been studied in detail in the horse but may be relevant to diseases such as laminitis. Identification of equine cell specific microvesicles was performed by developing a panel of cross reactive antibodies to use in flow cytometry to detect microvesicles of platelet, leucocyte and endothelial origin in plasma from healthy ponies and those predis...
Glycosphingolipids of porcine, bovine, and equine pericardia as potential immune targets in bioprosthetic heart valve grafts.
Xenotransplantation    June 22, 2018   Volume 25, Issue 5 e12406 doi: 10.1111/xen.12406
Barone A, Benktander J, Whiddon C, Jin C, Galli C, Teneberg S, Breimer ME.Pericardial tissue from various animal species is utilized for the production of the bioprosthetic heart valves (BHV) used clinically. Experimental data show that the eventual breakdown of BHV is partly due to immunological interactions with carbohydrate tissue antigens. To understand these processes, we have examined the glycolipid-based carbohydrate antigens in naïve porcine, bovine, and equine pericardia. Total non-acid and acid glycosphingolipid fractions were isolated from porcine, bovine, and equine pericardia, and individual glycolipid compounds were characterized by thin-layer chromat...
Cross-modal perception of human emotion in domestic horses (Equus caballus).
Scientific reports    June 21, 2018   Volume 8, Issue 1 8660 doi: 10.1038/s41598-018-26892-6
Nakamura K, Takimoto-Inose A, Hasegawa T.Humans have domesticated many kinds of animals in their history. Dogs and horses have particularly close relationships with humans as cooperative partners. However, fewer scientific studies have been conducted on cognition in horses compared to dogs. Studies have shown that horses cross-modally distinguish human facial expressions and recognize familiar people, which suggests that they also cross-modally distinguish human emotions. In the present study, we used the expectancy violation method to investigate whether horses cross-modally perceive human emotions. Horses were shown a picture of a ...
Expression of pro-apoptotic markers is increased along the osteochondral junction in naturally occurring osteochondrosis.
Bone reports    June 21, 2018   Volume 9 19-26 doi: 10.1016/j.bonr.2018.06.003
Semevolos SA, Duesterdieck-Zellmer KF, Larson M, Kinsley MA.Osteochondrosis (OC) is a naturally occurring disease of the articular-epiphyseal cartilage and subchondral bone layers, leading to pain and decreased mobility. The objective of this study was to characterize gene and protein expression of apoptotic markers in chondrocytes surrounding cartilage canals and along the osteochondral junction of osteochondrosis (OC)-affected and normal cartilage, using naturally occurring disease in horses. Paraffin-embedded osteochondral samples (6 OC, 8 normal controls) and cDNA from chondrocytes captured with laser capture microdissection (4 OC, 6 normal control...
Recovery of horses from general anesthesia after induction with propofol and ketamine versus midazolam and ketamine.
Journal of the American Veterinary Medical Association    June 19, 2018   Volume 253, Issue 1 101-107 doi: 10.2460/javma.253.1.101
Jarrett MA, Bailey KM, Messenger KM, Prange T, Gaines B, Posner LP.OBJECTIVE To evaluate quality of recovery from general anesthesia in horses after induction with propofol and ketamine versus midazolam and ketamine. DESIGN Prospective randomized crossover study. ANIMALS 6 healthy adult horses. PROCEDURES Horses were premedicated with xylazine (1.0 mg/kg [0.45 mg/lb], IV), and general anesthesia was induced with midazolam (0.1 mg/kg [0.045 mg/lb], IV) or propofol (0.5 mg/kg [0.23 mg/lb], IV), followed by ketamine (3.0 mg/kg [1.36 mg/lb], IV). Horses were endotracheally intubated, and anesthesia was maintained with isoflurane. After 60 minutes, horses were giv...
Treatment of Retained Fetal Membranes in the Mare-A Practitioner Survey.
Frontiers in veterinary science    June 19, 2018   Volume 5 128 doi: 10.3389/fvets.2018.00128
Warnakulasooriya DN, Marth CD, McLeod JA, Hanlon DW, Krekeler N.Retained fetal membranes (RFM) is a common post-partum problem in mares for which the treatment is highly variable. The aim of this study was (i) to investigate the different treatments used by equine practitioners for RFM and (ii) to determine if there is a difference between treatments used by reproductive specialists and general equine practitioners. Information regarding treatment of RFM was sought from veterinary practitioners via a survey and this was compared to recommendations in the current literature. The survey was sent out to equine veterinarians and mixed practitioners with a high...
Face, construct, and concurrent validity of a simulation model for laparoscopic ovariectomy in standing horses.
Journal of the American Veterinary Medical Association    June 19, 2018   Volume 253, Issue 1 92-100 doi: 10.2460/javma.253.1.92
Elarbi MM, Ragle CA, Fransson BA, Farnsworth KD.OBJECTIVE To develop and validate a simulation model for laparoscopic ovariectomy in standing horses. DESIGN Prospective cohort study. SAMPLE 15 third-year veterinary students and 4 equine surgeons with experience in laparoscopy. PROCEDURES A simulation model that mimicked laparoscopic ovariectomy in standing horses was developed. Face validity of the model was determined with a questionnaire completed by the equine surgeons. Construct validity was determined by comparing performance scores (based on time to completion and accuracy completing various operative tasks) for simulated laparoscopic...
Comparison of protective efficacies between intranasal and intramuscular vaccination of horses with a modified live equine herpesvirus type-1 vaccine.
Veterinary microbiology    June 19, 2018   Volume 222 18-24 doi: 10.1016/j.vetmic.2018.06.015
Bannai H, Nemoto M, Tsujimura K, Yamanaka T, Kokado H, Kondo T, Matsumura T.Immune responses were compared after intranasal (IN) and intramuscular (IM) vaccination of horses with a modified live equine herpesvirus type-1 (EHV-1) vaccine, and the protective effect after EHV-1 challenge was evaluated. IN- and IM-vaccinated groups (n = 5 each) showed significant rises in serum virus-neutralizing titers with increased levels of IgGa and IgGb antibodies after the first vaccination (P < 0.05). In nasal secretions, the IN group had significantly increased levels of IgA antibodies after vaccination (P < 0.05), whereas the response of the IM group was dominat...
[Clinical signs in late pregnant mares].
Tierarztliche Praxis. Ausgabe G, Grosstiere/Nutztiere    June 14, 2018   Volume 46, Issue 3 164-171 doi: 10.15653/TPG-180125
Neuhauser S, Gösele P, Handler J.During the peripartal period, interpretation of basic clinical signs may be challenging. In the present study, heart rate (HR), respiratory rate (RR) and body temperature (BT) were evaluated in healthy mares of different breed types and compared to reference values for adult horses from the literature. Methods: During daily physical exams of periparturient mares, the HR, RR and BT were evaluated. Differences according to the horse's size were investigated and in large breeds, the influence of dystocia or retained placenta was analysed. Results: During the last weeks before parturition (a. p.),...
Human Demonstration Does Not Facilitate the Performance of Horses (Equus caballus) in a Spatial Problem-Solving Task.
Animals : an open access journal from MDPI    June 13, 2018   Volume 8, Issue 6 doi: 10.3390/ani8060096
Burla JB, Siegwart J, Nawroth C.Horses’ ability to adapt to new environments and to acquire new information plays an important role in handling and training. Social learning in particular would be very adaptive for horses as it enables them to flexibly adjust to new environments. In the context of horse handling, social learning from humans has been rarely investigated but could help to facilitate management practices. We assessed the impact of human demonstration on the spatial problem-solving abilities of horses during a detour task. In this task, a bucket with a food reward was placed behind a double-detour barrier ...
Investigation of the treatment of sand accumulations in the equine large colon with psyllium and magnesium sulphate.
Veterinary journal (London, England : 1997)    June 13, 2018   Volume 238 22-26 doi: 10.1016/j.tvjl.2018.06.005
Niinistö KE, Ruohoniemi MO, Freccero F, Raekallio MR.Enteropathy associated with sand accumulation in the large colon of horses has been reported worldwide. Intestinal sand accumulations are commonly treated medically, but randomised controlled clinical trials on horses are scarce. This prospective study evaluated the efficacy of an enterally administered combination of psyllium and magnesium sulphate (MgSO4) for the removal of large colonic sand accumulations in horses without clinical signs of acute colic. The two groups comprised 20 untreated control horses and 20 horses treated with 1g/kg bodyweight (bwt) of psyllium and 1g/kg bwt of MgSO4 a...
Using quarterly earnings to assess racing performance in 66 thoroughbreds after transendoscopic laser surgery for treatment of epiglottic entrapment.
Veterinary surgery : VS    June 13, 2018   Volume 47, Issue 5 605-613 doi: 10.1111/vsu.12907
Kieffer PJ, Aceto H, Stefanovski D, Parente EJ.To assess the outcome of transendoscopic laser surgery for the treatment of epiglottic entrapment (EE) and determine the influence of preoperative morphological characteristics on outcomes. Methods: Retrospective cohort study. Methods: Thoroughbred racehorses treated with transendoscopic laser surgery (n = 66) and untreated cohorts (n = 132). Methods: Medical, surgical, and race records of 66 horses treated with transendoscopic laser surgery were compared with untreated cohorts randomly selected from their last race presurgery. Postsurgery data were collated as number of starts and rac...
Comparison of two agar gel immunodiffusion protocols for diagnosing equine infectious anemia.
The Journal of veterinary medical science    June 12, 2018   Volume 80, Issue 8 1245-1247 doi: 10.1292/jvms.18-0103
Nemoto M, Yamanaka T, Bannai H, Tsujimura K, Ueno T, Mekata H, Yoshida A, Koyama A, Kokado H.This study compared agar gel immunodiffusion (AGID) protocols for diagnosing equine infectious anemia. Two commercial testing kits were used: one following the Japanese Act on Domestic Animal Infectious Diseases Control and one following the World Organisation for Animal Health (OIE) manual. From 651 samples tested, both protocols gave identical results for 647 samples (23 samples tested positive; 624 tested negative). Non-specific reactions were observed in 21 samples testing negative by the Japanese protocol, but none were observed with the OIE protocol. The kappa coefficient value was 0.962...
Equine mesenchymal stromal cells from different tissue sources display comparable immune-related gene expression profiles in response to interferon gamma (IFN)-γ.
Veterinary immunology and immunopathology    June 11, 2018   Volume 202 25-30 doi: 10.1016/j.vetimm.2018.06.008
Cassano JM, Fortier LA, Hicks RB, Harman RM, Van de Walle GR.Mesenchymal stromal cells (MSC) have the therapeutic potential to decrease inflammation due to their immunomodulatory properties. They can be isolated from various tissue sources such as bone marrow, adipose tissue, and blood, but it is unknown how the tissue source of origin affects the responses of MSC to inflammatory stimuli. Here, we conceptually addressed this question by evaluating the immune-related gene expression profiles of equine MSC from different tissue sources in response to interferon gamma (IFN-γ) stimulation, with the goal to determine if there is a preferable MSC source for ...
Comparison of rider stability in a flapless saddle versus a conventional saddle.
PloS one    June 6, 2018   Volume 13, Issue 6 e0196960 doi: 10.1371/journal.pone.0196960
Clayton HM, Hampson A, Fraser P, White A, Egenvall A.The purpose of a saddle is to improve the rider's safety, security, and comfort, while distributing the forces exerted by the rider and saddle over a large area of the horse's back without focal pressure points. This study investigates the effects on rider stability of an innovative saddle design that differs from a conventional saddle in having no flaps. Five horses were ridden by their regular rider in their usual saddle and in a flapless saddle. A pressure mat (60 Hz) placed between the saddle and the horse's back was used to determine the position of the center of pressure, which represent...
Discovery of a novel species, Theileria haneyi n. sp., infective to equids, highlights exceptional genomic diversity within the genus Theileria: implications for apicomplexan parasite surveillance.
International journal for parasitology    June 6, 2018   Volume 48, Issue 9-10 679-690 doi: 10.1016/j.ijpara.2018.03.010
Knowles DP, Kappmeyer LS, Haney D, Herndon DR, Fry LM, Munro JB, Sears K, Ueti MW, Wise LN, Silva M, Schneider DA, Grause J, White SN, Tretina K....A novel apicomplexan parasite was serendipitously discovered in horses at the United States - Mexico border. Phylogenetic analysis based on 18S rDNA showed the erythrocyte-infective parasite to be related to, but distinct from, Theileria spp. in Africa, the most similar taxa being Theileria spp. from waterbuck and mountain zebra. The degree of sequence variability observed at the 18S rDNA locus also suggests the likely existence of additional cryptic species. Among described species, the genome of this novel equid Theileria parasite is most similar to that of Theileria equi, also a pathogen of...
Magnetic Motor Evoked Potential Recording in Horses Using Intramuscular Needle Electrodes and Surface Electrodes.
Journal of equine veterinary science    June 4, 2018   Volume 68 101-107 doi: 10.1016/j.jevs.2018.05.218
Rijckaert J, Pardon B, Van Ham L, van Loon G, Deprez P.To date, motor evoked potential (MEP) recording in animals is often performed using intramuscular monopolar needle electrodes. Their placement and use has several disadvantages. Adhesive surface electrodes appear to be attractive because they are painless and easy to place. Because these are not used in horses, a scouting study is performed to (1) explore the applicability of surface electrodes in horses (2) determine the repeatability of motor latency times (MLTs) and amplitude measurements, and (3) to investigate if MLTs and amplitude values of surface electrode recordings were similar to in...
5α-dihydroprogesterone concentrations and synthesis in non-pregnant mares.
The Journal of endocrinology    June 2, 2018   Volume 238, Issue 1 25-32 doi: 10.1530/JOE-18-0215
Conley AJ, Scholtz EL, Legacki EL, Corbin CJ, Knych HK, Dujovne GD, Ball BA, Moeller BC, Stanley SD. and evidence indicates that the bioactive, 5α-reduced progesterone metabolite, 5α-dihydroprogesterone (DHP) is synthesized in the placenta, supporting equine pregnancy, but its appearance in early pregnancy argues for other sites of synthesis also. It remains unknown if DHP circulates at relevant concentrations in cyclic mares and, if so, does synthesis involve the non-pregnant uterus? Jugular blood was drawn daily from cyclic mares ( = 5). Additionally, ovariectomized mares (OVX) and geldings were administered progesterone (300 mg) intramuscularly. Blood was drawn before and after t...
Some maternal lineages of domestic horses may have origins in East Asia revealed with further evidence of mitochondrial genomes and HVR-1 sequences.
PeerJ    June 1, 2018   Volume 6 e4896 doi: 10.7717/peerj.4896
Ma H, Wu Y, Xiang H, Yang Y, Wang M, Zhao C, Wu C.There are large populations of indigenous horse () in China and some other parts of East Asia. However, their matrilineal genetic diversity and origin remained poorly understood. Using a combination of mitochondrial DNA (mtDNA) and hypervariable region (HVR-1) sequences, we aim to investigate the origin of matrilineal inheritance in these domestic horses. Methods: To investigate patterns of matrilineal inheritance in domestic horses, we conducted a phylogenetic study using 31 mtDNA genomes together with 317 others from the GenBank. In terms of the updated phylogeny, a total of 5,180 horse mit...
First Radiological Study of a Complete Dental Ontogeny Sequence of an Extinct Equid: Implications for Equidae Life History and Taphonomy.
Scientific reports    May 31, 2018   Volume 8, Issue 1 8507 doi: 10.1038/s41598-018-26817-3
Domingo MS, Cantero E, García-Real I, Chamorro Sancho MJ, Martín Perea DM, Alberdi MT, Morales J.The sequence of cheek teeth mineralization, eruption, and replacement of an extinct horse species is here documented with radiological techniques for the first time thanks to the exceptional preservation of Hipparion sp. mandibles from Cerro de los Batallones (Madrid Basin, Spain). The sequence of dental ontogeny in mammals provides valuable insights about life history traits, such as the pace of growth, and about the mode of formation of fossiliferous assemblages. We have determined that the order of permanent cheek teeth mineralization and eruption of hipparionine horses is m1, m2, (p2, p3),...
A potential regulatory region near the EDN3 gene may control both harness racing performance and coat color variation in horses.
Physiological reports    May 31, 2018   Volume 6, Issue 10 e13700 doi: 10.14814/phy2.13700
Jäderkvist Fegraeus K, Velie BD, Axelsson J, Ang R, Hamilton NA, Andersson L, Meadows JRS, Lindgren G.The Swedish-Norwegian Coldblooded trotter and the heavier North-Swedish draught horse both descend from the North-Swedish horse, but the Coldblooded trotters have been selected for racing performance while the North-Swedish draught horse is mainly used for agricultural and forestry work. By comparing the genomes of Coldblooded trotters, North-Swedish draught horses and Standardbreds for a large number of single-nucleotide polymorphisms (SNPs), the aim of the study was to identify genetic regions that may be under selection for racing performance. We hypothesized that the selection for racing p...
Comparison of fecal egg counting methods in four livestock species.
Veterinary parasitology    May 26, 2018   Volume 257 21-27 doi: 10.1016/j.vetpar.2018.05.015
Paras KL, George MM, Vidyashankar AN, Kaplan RM.Gastrointestinal nematode parasites are important pathogens of all domesticated livestock species. Fecal egg counts (FEC) are routinely used for evaluating anthelmintic efficacy and for making targeted anthelmintic treatment decisions. Numerous FEC techniques exist and vary in precision and accuracy. These performance characteristics are especially important when performing fecal egg count reduction tests (FECRT). The objective of this study was to compare the accuracy and precision of three commonly used FEC methods and determine if differences existed among livestock species. In this study, ...
Effect of embryo transfer technique on the likelihood of pregnancy in the mare: a comparison of conventional and Wilsher’s forceps-assisted transfer.
The Veterinary record    May 24, 2018   Volume 183, Issue 10 323 doi: 10.1136/vr.104808
Cuervo-Arango J, Claes AN, Stout TA.The aim of this study was to compare the success of embryo transfer (ET) performed by veterinarians with different degrees of experience using one of two ET techniques. Over three years, 179 embryos were transferred by three operators with moderate to high experience using a 'conventional' manual technique, and 170 embryos were transferred by four operators with little or no previous ET experience using a 'Wilsher' technique (Polansky speculum and Wilsher's cervical forceps). The pregnancy status of recipient mares at the first pregnancy diagnosis and the embryo loss by the last examination we...
Seroprevalence of Equine Herpesviruses 1 and 9 (EHV-1 and EHV-9) in Wild Grévy’s Zebra ( Equus grevyi) in Kenya.
Journal of wildlife diseases    May 24, 2018   Volume 54, Issue 4 848-851 doi: 10.7589/2018-01-003
Guevara L, Abdelgawad A, Onzere C, Greenwood AD, Davidson Z, Bishop R, Mutinda M.Equid herpesviruses types 1 (EHV-1) and 9 (EHV-9) are unusual among herpesviruses in that they lack strong host specificity, and the full extent of their host range remains unclear. The virus establishes latency for long periods and can be reactivated and shed, resulting in clinical disease in susceptible species. A sensitive and specific peptide-based enzyme-linked immunosorbent assay was developed to study the seroprevalence of both viruses in a broad range of species among both wild and captive populations. We used this assay to study the seroprevalences of EHV-1 and EHV-9 in a natural popu...
According to mitochondrial DNA evidence, Parascaris equorum and Parascaris univalens may represent the same species.
Journal of helminthology    May 24, 2018   Volume 93, Issue 3 383-388 doi: 10.1017/S0022149X18000330
Gao JF, Zhang XX, Wang XX, Li Q, Li Y, Xu WW, Gao Y, Wang CR.Parascarosis is caused mainly by parasitic infections with Parascaris equorum and Parascaris univalens, the most common ascarid nematodes, in the small intestine of equines. Parascarosis often causes severe illness and even death in foals and yearlings. In this study, we obtained the complete sequence of the P. equorum mitochondrial (mt) genome and compared its organization and structure with that of P. equorum Japan isolate (nearly complete), and the complete mtDNA sequences of P. univalens Switzerland and USA isolates. The complete mtDNA genome of P. equorum China isolate is 13,899 base pair...
The grazing gait, and implications of toppling table geometry for primate footfall sequences.
Biology letters    May 18, 2018   Volume 14, Issue 5 20180137 doi: 10.1098/rsbl.2018.0137
Usherwood JR, Smith BJH.Many medium and large herbivores locomote forwards very slowly and intermittently when grazing. While the footfall order during grazing is the same as for walking, the relative fore-hind timing-phasing-is quite different. Extended periods of static stability are clearly required during grazing; however, stability requirements are insufficient to account for the timing. Aspects of relatively rapid rolling and pitching-toppling due to the resistance of the back to bending and twisting-can be included in a simplifying geometric model to explain the observation that, in grazing livestock, a step f...
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