376 Journal of Equine Veterinary Science August 2006
Current Research
PROSPECTIVE STUDY OF PRE-SALE RADIO-GRAPHS OF THOROUGHBRED YEARLINGS
August 2003–April 2006
Orthopedic (bone) disease and racetrack injuriesrepresent a major cause of economic loss for the horseracing industry. The routine radiographic (x-ray) exam-ination of yearling Thoroughbreds before sale providesa unique resource to researchers interested in orthope-dic disease in horses.
This project aims to identify the incidence of radio-graphic abnormalities in yearling Thoroughbred horsespresented for sale in Australia. The study also will pro-vide an objective assessment of the impact these radio-graphic findings have on racing career.
Current Progress The researchers have catalogued 2,412 sets of x-
rays from Thoroughbred yearlings presented for salein the 2003 season. This represents 88% of all radio-graph sets submitted to the repositories at MagicMillions, Perth Premier and Adelaide yearling salesand William Inglis Melbourne Premier, SydneyClassic, Sydney Easter, and Scone yearling sales in2003. Over 1,500 of the x-ray sets have been reviewed.The x-rays were examined for the presence or absenceof orthopedic abnormalities ranging from bone cystsin stifle joints to osteochondrosis dissecans (OCD) le-sions in fetlocks.
The construction of a database to hold radio-graphic and race performance information has beencompleted. Horse and sale data for 3,905 (radio-graphed and non-radiographed) yearlings soldthrough the 2003 sales have been entered into thedatabase. Details of the racing careers of these horseshave been entered for the 2-year-old racing season.The 3-year-old racing season for these horses has re-
cently finished, and data entry of performance recordsis underway. An analysis of the completed databasewill enable the researchers to assess the impact thatradiologic abnormalities have on the racing abilities ofyearlings that have been x-rayed. The database alsowill allow a comparison of the yearlings that were x-rayed and those that were not x-rayed.
This project will be of benefit to the Thoroughbredhorse industry, especially those involved in the breed-ing, sale, and purchase of racehorses, and provide infor-mation about the incidence of abnormal findings inyoung racehorses before entering training.
Researchers:Prof. Andrew Clarke et al.
Veterinary Clinical Centre, University of MelbourneEmail: [email protected]
Ph: (03) 9731 2314
MANAGEMENT STRATEGIES FOR REDUCINGTHE RISK OF RHODOCOCCAL PNEUMONIA(‘RATTLES’) ON STUDS
August 2003–May 2006
Rhodococcus equi (R. equi) is a serious bacterial in-fection that can be a major cause of pneumonia inyoung foals. Infected foals are said to be suffering “rat-tles.” Few options exist for control, and current methodsof prevention rely on reducing fecal contamination anddust on studs. There is limited understanding of themost effective way to control fecal contamination anddust, or whether ineffective control of these factors ac-counts for a higher rate of the incidence and seriousnessof the infection on some stud farms.
The aim of this project is to specifically examinedifferent strategies that influence the population of vir-ulent R. equi and follows previous important researchfrom this group, funded by RIRDC.
Previous studies have shown that the presence ofhorse feces in soil greatly stimulates the growth of R.equi, and it was further discovered that volatile fattyacids in the horse feces were most likely responsible.Other growth studies on R. equi have not taken into
Equine Projects Update, September 2005, Part TwoAustralian Government
0737-0806/$ - see front matter© 2006 Elsevier Inc. All rights reserved.doi:10.1016/j.jevs.2006.06.004
Volume 26, Number 8 377
account recent findings that only a small percentageof R. equi in soil are able to cause “rattles.” Only R.equi that contain a specific virulence plasmid (some-thing in the structure of the bacterium that makes itinfective) can cause “rattles.” Virulent strains growmore slowly than other strains when exposed tohigher temperatures. These findings suggest that pre-vious studies examining the effect of environmentalchanges on horse studs may have overlooked themost significant effects because they could not dis-tinguish the small minority of R. equi responsible fordisease in foals. The researchers’ previous RIRDC-supported studies have shown that the proportion ofvirulent R. equi in soil may be increased in sandy andacid soils, and the areas on studs that appear to posethe highest risk are holding pens and laneways.Although this information suggests that environmen-tal manipulation is likely to have a significant effecton the risk of disease, the supporting evidence is es-sentially anecdotal.
The researchers also have shown in previous stud-ies that infected foals excrete R. equi in their expiredair, so there is a suggestion that keeping infected foalsin contact with uninfected foals may be a significantrisk factor. Foal breath sampling is a useful, noninva-sive diagnostic assay and can be useful for monitoringtreatment.
This project forms part of a wider collaborationwith Dr. Des Leadon of the Irish Equine Centre, whois using methods developed by Dr. Browning and hisresearch team to perform parallel studies on IrishStuds and with Dr. Michael Heuzenroeder, who hasbeen developing serological tests in another RIRDC-funded project.
Current Progress The researchers have investigated a variety of farm
factors that may influence the level of aerosol exposureto virulent R. equi in foals.
Early results suggest that intensive irrigation oflaneways and pen areas can reduce the prevalence andseverity of R. equi pneumonia on farms. Studies to de-termine the effect of top dressing soil with lime, herdsize, and management techniques to alter soil textureare continuing through the current foaling season.
In Ireland, researchers are investigating the affect ofalternate bedding materials on the prevalence of R.equi. In the next foaling season, the researchers will in-vestigate chemical fogging of stables.
Once tested, strategies developed in this project willbe used to formulate recommendations for studs to de-
crease the risk of development of “rattles,” thus reduc-ing the incidence of the disease.
ResearchersDr. Glenn Browning, Dr. Terry Lowis,
Dr. James Gilkerson, and Dr. Gary MuscatelloVeterinary Preclinical Centre, University of Melbourne
Email: [email protected] Ph: (03) 8344 7342
UNDERSTANDING AND MANAGING VARIABLESTARCH DIGESTION IN THE HORSE
July 2003–June 2006
The objective of this study is to demonstrate that,under commercial training conditions, those horses feddiets likely to produce extensive fermentation of starchin the hindgut have more problems with respect tohealth, adverse behavior, and poor performance thansimilar animals fed diets likely to produce little or nofermentable starch in the hindgut.
Research is focusing on the identification of simplemeasurements that can be made on individual horses todetermine their ability to digest starch efficiently. Onceidentified, these measurements will enable the objec-tive tailoring of diets to meet the requirements and abil-ity of individual horses. The researchers are also inves-tigating combinations of exogenous enzymes (amylaseand amylogucosidase) to ensure that starch is com-pletely digested in the small intestine before enteringthe hindgut.
Current Progress Fecal samples have been taken from Thoroughbred
horses at a series of commercial training establishmentsin Grafton, NSW. The samples have been studied andan assessment has been made of the variability of fecalpH during the day and between different days for indi-vidual training establishments. Differences in horsefecal matter pH between different training establish-ments also have been assessed. The results show thatthere is considerable variation between establishmentsand between horses within establishments. This sug-gests that diet is not the only factor that contributes tothe variability of pH.
Fecal and grain samples have been stored for anal-ysis of starch, volatile fatty acids, and digestibility to de-termine whether the pH measurements correlate wellwith other indicators of hindgut fermentation.
Methods have been developed to assess behav-ioral characteristics that can be monitored and cor-
378 Journal of Equine Veterinary Science August 2006
related to gut parameters to determine whetherstarch digestion is associated with behavior inhorses. Changes in hindgut fermentation patternsmay be quickly reflected in behaviors, and this workis continuing.
The researchers also are currently investigatingmethods to optimize hindgut conditions and minimizethe potential effects of an acidic hindgut.
ResearcherDr. Geoff Hinch
School of Rural Science and Agriculture, University of New England
Email: [email protected]
LAMINITIS PREVENTIVE AND THERAPEUTICSTRATEGIES
October 2004–May 2007
A laminitis research team led by Dr. Chris Pollitthas made important progress in the understanding oflaminitis through their previous extensive research sup-ported by RIRDC since 1995.
In this project, the research team aims to under-stand how laminitis develops at the molecular level toformulate strategies for diagnosis, prevention, andtreatment.
Current Progress The researchers have shown that clinical laminitis
can be prevented in horses through the use of cryother-apy (cold water bath).
In experiments in which laminitis was induced,horses in the treatment group had all four feet im-mersed in a cold water bath (2°C) for 3 days during theearly stages of laminitis. The treated horses did not de-velop laminitis and showed no signs of lameness 4 daysafter cryotherapy ceased. Horses in the control groupdeveloped laminitis and lameness.
The researchers have made progress in their studieson the factors that trigger the development of laminitis.Magnetic resonance imaging (MRI) and tissue biopsyare being used to study the effects of agents that inhibitthe chemicals that are known to be involved in the de-velopment of laminitis. These studies are continuing.
ResearcherDr. Chris Pollitt
School of Veterinary Science, University of QueenslandEmail: [email protected]
Ph: (07) 3365 2063
ROLE OF BACTERIA AND LACTIC ACID IN THEPATHOGENESIS OF GASTRIC ULCERATION
August 2004–July 2007Gastric (stomach) ulceration is one of the most
common and significant problems of horses in training,with 70 to 80% or more horses affected. Gastric ulcera-tion can cause weight loss and poor performance thatcan be severe enough to end a horse’s racing career.
Many treatments are available for gastric ulcers inhorses, but they are expensive, are not highly effective,and are prohibited for use close to race days.
Gastric ulcers result from feeding and managementpractices. Racehorses are usually fed twice per day on agrain-rich diet, and they are usually fasted for an ex-tended period before exercise. The combination of in-creased gastric acid production during exercise, reduc-tion in saliva production is likely attributable to alow-fiber diet, and indoor confinement contributes tothe development of gastric ulcers in horses. A suddenincrease in blood sugar levels may elevate gastrin pro-duction, which in turn elevates gastric acid production.This leads to prolonged periods of exposure of unpro-tected regions of the stomach to acid, causing ulcers.
Recent research in the United States has shownthat volatile fatty acids damage the lining of the stom-ach more severely than normal gastric acids. This lendssupport to the theory that bacteria play an importantrole in the development of gastric ulcers.
This project aims to establish the involvement oflactic acid-producing bacteria and their products,namely volatile fatty acids and lactic acid, in the devel-opment of gastric ulcers in horses. The study will alsodetermine the effect of different diets on the contribu-tion by bacteria to the buildup of lactic acid and volatilefatty acids in the stomach.
Current ProgressThe stomach contents and stomach lining have been
collected from 20 horses post mortem. Using standard laboratory procedures, bacterial isolates were extractedfrom the samples of stomach contents and stomach lin-ing. Further procedures enabled the identification of thebacteria isolated from the samples. Early results showthat the most commonly isolated bacteria are thoseknown to be common to the environment and to thegastrointestinal tract. Samples of ulcerated stomachsshow a different bacterial population compared withnormal stomach samples. Further analysis is underwayto specify the differences between bacterial populationsin ulcerated stomachs compared with normal stomachs.
The discovery of the bacteria involved in the devel-opment of gastric ulcers in horses will lead to possiblespecific treatment and prevention strategies that will begreatly beneficial to the horse industry.
ResearcherDr. Rafat Al Jassim
School of Animal Studies, University of QueenslandEmail: [email protected]
Ph: (07) 5460 1521
RIRDC shall not be responsible in any mannerwhatsoever to any person who relies, in whole or inpart, on the contents of these reports unless authorizedin writing by the Managing Director of RIRDC.
Reprinted from RIRDC website:http://www.usyd.edu.au/rirdc/projects/study17.html
Please address any questions or comments to: MellisaOfford, [email protected] (Assistant Editor of the
RIRDC Equine Research News).
Volume 26, Number 8 379
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