Dairy farm guidelines for BJD control


Dairy farm guidelines for BJD control

Bovine Johnes Disease (BJD)Dairy farm guidelinesfor BJD controlBEST PRACTICE RECOMMENDATIONSfor managing the risk of BJD in Australian dairy herdswww.dairyaustralia.com.au/bjd

ContentsPart 1. Introduction 2BJD in the Australian dairy industry 3BJD: a whole farm approach 6Part 2. Key farm recommendationsfor managing the risks 8Minimise new infections 9Avoid introducing BJD 9Remove cattle shedding BJD 9Identifying and managing your risk 10Part 3. Frequently asked questions 14Question 1 Can calves be born already infected with BJD? 15Question 2 Can sheep with OJD infect cattle? 15Question 3Question 4What is the risk of spreading BJD viairrigation canals and shared waterways? 15What programs are there in Australiafor BJD control and market assurance? 16Question 5 How can BJD contaminated land be managed? 18Question 6 What’s the BJD risk from semen and embryos? 19Question 7 Does early calf removal affect the welfareof the cow or calf? 19Question 8 Can floods spread BJD? 19Question 9 BJD and milk quality assurance:what are the issues? 20Question 10 How useful are the diagnostic tests for BJD? 20

Part 1. IntroductionBovine Johne’s Disease (BJD)in the Australian dairy industryKey pointsIt is relatively common for dairyherds in South Eastern Australia tohave BJD.BJD control benefits both thedairy industry and individual farmers.Australia has a national, across-industrystrategy for managing BJD.Many other countries are activelymanaging BJD.Control of BJD centres aroundthree key areas:− minimising new infections in calves;− avoiding introducing BJD; and− removing cattle that are sheddingthe bacteria.What is BJD?Bovine Johne’s disease (BJD) is a chronic,incurable disease of adult cattle causedby a hardy, slow-growing bacterium calledMycobacterium paratuberculosis.Cattle usually only become infectedas calves less than 12 months of age.Generally no symptoms are seen until theanimals are at least four years old. Whenclinical signs do occur they include a lossof milk production and body weight overseveral weeks, followed by persistentdiarrhoea that is unresponsive to treatment.The animal will then waste away overweeks to months until it eventually dies.The presence of the disease in a herd isnotifiable to the State Government andmovement restrictions may be placed oncattle from affected herds in some States.Although live animals can be tested forBJD, infection is difficult to detect reliablyin all animals in early stages. For example,a typical 200-cow dairy herd infected withBJD could expect to see only a handful ofclinical cases each year. If the herd wasblood tested, around 2% (four of the 200animals) may be detected. However, dueto the low sensitivity of the blood test thereare likely to be around 10% (20 animals)infected with BJD in the herd.Dairy farm guidelines for BJD control 3

Part 1. IntroductionFarm benefitsof controlling BJDReduced deaths, reduced early cullingand improved slaughter weightsFarmers who are active in managing BJDcan reduce the economic impact of thedisease. Deaths from clinical cases arejust the tip of the iceberg; losses alsooccur through premature culling andlower slaughter weights for cull cows.Improved milk production fromnon-infected cattleMany studies have shown that cattleinfected with BJD produce less milk thannon-infected cows, without showing overtsigns of disease. In the lactation beforean infected cow starts to scour, her milkproduction is reduced by around 5 to 15%.Hygienic calf-rearing programs helpto reduce spread of other infectiousdiseases of calvesAnecdotal evidence suggests that thehealth of calves can be improved byminimising the calves’ exposure toadult cow faeces. While no major studieshave been documented, farmers havereported less calf disease and lowermortalities after implementing BJDcontrol programs for calves.Potential to increase asset valueswith good BJD managementHerds that have systems in place to ensurethey are a low risk for BJD may attractmore buyers for their cattle and land, andconsequently higher prices. Participationin a BJD market assurance program willencourage buyers from across Australiabecause of their ability to move purchasedcattle between zones. This is particularlyrelevant for stud breeders.4 Dairy farm guidelines for BJD control

Part 1. IntroductionDairy industry benefitsof controlling BJDInternational market risk-managementAustralia’s animal health status has thepotential to be used as a barrier to trade.It is in the best interests of the Australiandairy industry to be pro-active in BJDcontrol and so minimise the potential fortrade restrictions in the future. Countriessuch as the Netherlands, Sweden, Norway,the US, Canada and Japan all activelymanage BJD. Japan aims to eradicateBJD from its national herd and has amajor national program in place.BJD is considered by many importingcountries in their animal healthstatements and many require varioustesting procedures and assurancesprior to export.Consolidate Australia’s alreadyfavourable animal disease statusAustralia has an enviable position in theworld because it is free of many seriouscattle diseases such as tuberculosis,brucellosis, mad-cow disease andfoot-and-mouth disease. This statusallows us relatively easy access into theinternational live animal market. In recentyears, dairy farmers have benefited throughthe export of tens of thousands of dairyheifers to many countries around the globe.Australia is the only country that hasa recognised BJD-free dairy region(Western Australia). In Australiandairy herds where BJD is present,the within-herd prevalence is alsogenerally much lower than reportedfrom overseas countries.Milk quality assuranceAlthough no definitive link has ever beenestablished, there is some internationalpublicity linking the bacteria which causesBJD with an incurable disease of humanscalled Crohn’s disease. This has raisedinterest in the issue and driven furtherresearch work. If a definitive link betweenBJD and Crohn’s disease is everestablished, there may be major implicationsfor the Australian and global dairy industries(see also Question 9, page 20).BJD reduces overalldairy industry productivityLosses from BJD are generally consideredmodest in comparison to diseases such asmastitis, metabolic diseases, fertility andlameness. However, cattle infected withBJD produce less milk in the 12-18 monthsprior to showing symptoms. This results ina significant loss of milk across the wholeof the dairy industry.Dairy farm guidelines for BJD control 5

Part 1. IntroductionBJD: a whole farm approachKey pointsBJD management practices shouldbe incorporated into all dairy farmingsystems, regardless of BJD status.Set realistic goals based on yourresources and capabilities.All farmers should aim to provide atleast a moderate level of assurance thattheir herd is a low risk for BJD infection.IntroductionThe majority of dairy farmers in Australiahave limited capacity to provide assurancesthat BJD is not likely to be present in theirherd. Whether you want to join an ‘official’assurance program or not, there are manypractical things that can be done on-farmtoday to help minimise the risk of spreadingor introducing BJD (Table 1).Set realistic goalsIf you are like many commercialdairy farmers and primarily focus onmilk income, selling only a few heifersand calves, you may not wish to investheavily in BJD assurance.If you already have an infected herd youwould already be aware that BJD cannotbe eradicated quickly. Many herds thatenrol in an approved test and controlprogram take a number of years beforethe herd tests are negative, and eventhen may never completely eliminatethe infection (see Question 10, page 20).Plan for the futureYour herd is a valuable asset and shouldbe managed carefully to minimise therisks of introducing unwanted diseases.Being able to offer some assurance thatyour cattle are low risk for BJD may bringfinancial rewards if you are planning to sellyour herd in the near future. Time will tellif a price premium develops in the marketplace for commercial cattle from BJDassured properties.International market pressures may alsoforce a rapid unpredictable change at anytime. Farmers engaged in a BJD assuranceprogram are in a better position to managethis business risk.6 Dairy farm guidelines for BJD control

Part 1. IntroductionTable 1. Different approaches to BJD based on desired level of interest.Interest in BJD managementLow Moderate HighGoal“I want to startsomewhere with BJDbut not test and notspend much!”“I’m keen to get ahigher Dairy Scoreand really startgetting on topof BJD.”“I’m all out forachieving thehighest level ofassurance I can!”TestingNot initially, butconsider it once allcalves reared under3-Step Plan are morethan 4 years old.Test whole herdor Check test 50animals to assesscurrent prevalence orpresence of BJD.Regular wholeherd testing of2+ year olds orjoin CattleMAP.Calf rearingImplement ahygienic calf program(e.g. 3-Step Plan)and/or othermeasures thatrequire minimalchanges tocurrent system.Implement ahygienic calf program(e.g. 3-Step Plan)and/or othermeasures thatrequire minimalchanges tocurrent system.Implement anaudited hygieniccalf-rearing program(e.g. JDCAP)HerdintroductionsMake low riskherd introductions –use Dairy Score (4+)cattle.Make low riskherd introductions –use Dairy Score (7+)cattle.Closed herd –or only CattleMAP(Dairy Score 8+)cattle.Culling policyCull high-risk animalsbased on non-testingdata (e.g. clinicalcases, cohorts,direct progeny)Cull high-risk animalsbased on herd testand consider furtherpreferential culling.Aggressively cullall high-risk animals.Other measuresRemove goats andalpaca, fix fences.Consider off-farmrearing of calves ifproperty is low risk.Secure all fences.Restrict accessto calf area bypersonnel.Dairy farm guidelines for BJD control 7

Part 2.Key farm recommendationsfor managing the risks8 Dairy farm guidelines for BJD control

Part 2. Key farm recommendations for managing the risksThere are three main components to managing the risks posed by BJDon the farm.Minimise new infectionsProtect calves from the sources ofBJD bacteria, especially minimiseany contact with adult faeces.Age resistance develops –by 12 months old calves arefairly resistant.Avoid introducing BJDBJD comes in on the back of a truck!BJD is usually introduced into a herdthrough a single infected animal.Take steps to know the risk withstock introductions.Use the Dairy Score to assessthe risk of BJD.If you don’t know the risk, focus onprotecting your calves from beingexposed to adult cattle and faeces.Semen and embryos are low risk forspreading BJD.Remove cattle shedding BJDIdentify and remove cattle that areshedding BJD as early as possible.This will reduce environmentalcontamination of the BJD bacteria.Blood testing will not identify all infectedanimals, but is a useful tool to identifythose animals most likely to be sheddingthe BJD bacteria.High-risk groups of animals can beidentified from testing results andpreferentially culled from the herdover time.Testing and culling positive cows is mosteffective when combined with BJD calfmanagement recommendations.RemovesheddersMinimisenew infectionsAvoidintroducing BJDDairy farm guidelines for BJD control 9

Part 2. Key farm recommendations for managing the risksIdentifying and managing your riskThe following set of questions is designed to help you quickly identifyareas for improvement in your management of the risk of BJD.Steps to minimise new infectionsMinimising new infections Poor Could be better GoodDo you take steps tomanage the cleanliness ofthe calving environment?Not very often. Sometimes. Yes, always stripgraze calvingpaddock.Yes, always cleancalving pad weekly.Do you removenewborn calves offtheir dams at leasttwice daily at calving?No.No, however I dotry to get themout once or twicea day.Yes, always,at least twice a day.Do you separate calvesfrom their mothers in thecalving area?Occasionally,however I alwaysmove them uplane to yards.Quite often.Yes, alwayscatch them inthe calving area.Do you feed milk from sickor medicated cows (i.e.blue milk) to your calves?Sometimes. Rarely. No, never, alwaysdiscard blue milk.Do you take steps toprevent milk and colostrumfor calves from beingsplashed withadult faeces?I occasionallydiscard acontaminatedbucket.I usually discarda contaminatedbucket.Yes, always,lids on vats and chuckaway milk with anymuck in it.Do you feed pooledcolostrum or milk tocalves?Most of the time. Sometimes. No, herdreplacements getmilk replacer powderor milk from low-riskcows.Do you have elevated feedbins, hay racks and watertroughs for calves?No, feed onthe ground.Some.Yes, all feed goes intoelevated bins.Do you use tank ortown water for calves?No.Not really, but wedo sediment outcanal water.Yes, always, only tankor town water.10 Dairy farm guidelines for BJD control

Part 2. Key farm recommendations for managing the risksSteps to minimise new infections (continued)Minimising new infections Poor Could be better GoodDo you use milk replacer? Very rarely. We are lookinginto it.Yes, always use it if wecan’t get enough lowriskmilk.Do you graze calves wheredairy effluent runoff ispresent or pasture hasbeen sprayed?Sometimes.I try to avoid it.Sometimescalves are inan adjacentpaddock.No, never.Do you use on-farm milkpasteurisation units?Do you use differentequipment to handlefeed and faeces?No. Sometimes. Yes.No, same. Sometimes. Yes, always usededicated feed-onlyequipment.Is the calf-rearing areaseparate from adult cattleand not exposedto effluent runoff?No.Calves are inan adjacentpaddock.Yes.Do calves have accessto any adult manure,boggy-swampy areasor open drains whenthey are less than12 months old?Do you rear calvesoff-farm?Do you encourageeveryone, including servicepersonnel & contractors toclean boots, vehicles andequipment before enteringthe calf area?Do you ever put cattle,alpaca, goats or deer inthe calf-rearing areas?Yes. Sometimes. No, never.Not usually. Sometimes. Yes, always.Not usually. Usually. Yes, always. We havesigns and tell everyone.It’s part of staff training.Sometimes. Very rarely. Never.Dairy farm guidelines for BJD control 11

Part 2. Key farm recommendations for managing the risksSteps to avoid introducing BJD onto the farmAvoid introducing BJD Poor Could be better GoodDo you source cowsfrom low-BJD risk (highDairy Score) herds?Do you protectyour calves fromexposure to manureof introduced stock?No. Sometimes. Yes, always from highestDairy Score we can get.Very rarely. Usually. Yes, always, calves nevergo near.Do you source bullsfrom low-risk sources?Notusually.Sometimes I askabout it.Yes, always from highestDairy Score we can get.Do you use semen andembryos to reduce therisk?No. Sometimes. Yes.Do you agist out animalsolder than 12 months?No.Sometimes, butI ask about risk.Yes, always,only adults go away.Do you testcattle for entryto shows?No.Sometimes, butI ask about BJDrisk.Yes, always,find out what is needed.12 Dairy farm guidelines for BJD control

Part 2. Key farm recommendations for managing the risksSteps to identify and remove cattle shedding the bacteriaRemoving shedders Poor Could be better GoodDo you understand thediagnostic tests for BJD?No.No, but I am goingto read up on it.Yes, I know what theydo and how best toapply them.Do you use the BJD testresults and other informationto preferentially cull cattle?No. Sometimes. Yes, always get ridof high-risk cows.Do you cull test-positivecattle as soon as possible?No.Sometimes, butwe usually letthem milk out.Yes, always cull oncewe get test results andalways before calving.Do you understand theregulatory implications ofhaving a test-positive herdin your region?No.No, but I will askabout it.Yes.Dairy farm guidelines for BJD control 13

Part 3.Frequently askedquestions14 Dairy farm guidelines for BJD control

Part 3. Frequently Asked QuestionsQuestion 1Can calves be born alreadyinfected with BJD?Key pointsProgeny from BJD infected cowsmay also be born infected with BJD.Reducing the number of clinicalinfections will help to reduce thechances of transmission to the calf.Cows with clinical signs of BJD areat very high risk of producing aninfected calf.Maternal progeny of clinical casesshould be culled.Question 2Can sheep with ovine Johne’sdisease (OJD) infect cattle?Key pointsSheep with OJD can infect cattlehowever the risk is relatively low.Sheep may become infected with BJD.The risk of transmission from sheepinfected with BJD to calves is probablyhigh.Avoid running sheep on pasture likelyto be grazed by dairy calves or heifers.Question 3What is the risk of spreadingBJD via irrigation canals andshared waterways?Key pointsThe BJD bacterium survives for longperiods in water and sediments.The bacteria become widespread inthe environment of infected cows andreadily spreads from manure to water.In the US, up to 50% of samplescollected from dairy exits, floors ofholding pens, common alleyways,lagoons, manure spreaders andmanure pits are contaminated.BJD bacteria are likely to bepresent in effluent drainage fromcontaminated sites.The risk of BJD spread in irrigation andshared waterways is potentially high ifherds with high prevalence are presentin the catchment.Dairy farm guidelines for BJD control 15

Part 3. Frequently Asked QuestionsQuestion 4What programs are there in Australia for BJD controland market assurance?National Dairy BJD Assurance ScoreThe National Dairy BJD Assurance Scoreis a voluntary, risk-based trading system,based on self assessment, for farmers tobetter manage the risk of BJD. Using theexisting programs, the Dairy Score ranksthe assurance measures, on a 0 to 10scale, of cattle being infected with BJD.The 10-point scale recognises the benefitsof good BJD practices: the higher thescore, the lower the risk. Recognition isgiven to herds enrolled in approved controlprograms, hygienic calf-rearing program,single test negative herds and the cattleBJD market assurance program.Full details of the Dairy Scoreare available from the website,www.dairyaustralia.com.au/bjd3-Step Calf PlanThe 3-Step Calf Plan is a voluntary,industry-driven program containing threeessential steps for minimising the spreadof BJD. The program is included as a‘best practice’ recommendation in alldairy company on-farm quality assurancemanuals, and can also be used to improvethe Dairy Score (see above) of cattle rearedunder this program.South Australia, DairyManaJDDairyManaJD is a voluntary BJD controlprogram launched in South Australiaduring 2005. To enrol in DairyManaJDa herd must have cattle tested, cull anyblood test reactors, agree to a calfmanagement program and be subjectto audit. Infected herds that enrol in theprogram are not subject to quarantine, butcan sell on disclosure of their Dairy Scoreto other herds.This program has seen a positive responsefrom dairy farmers. As of December 2007around 90% of dairy herds in SouthAustralia had enrolled and been tested inthe program. The program is funded by theSouth Australian beef cattle industry.Johne’s Disease Calf AccreditationProgram (JDCAP)The Johne’s Disease Calf AccreditationProgram (JDCAP) is managed by DPIVictoria. Calves reared under this programare considered a very low risk of havingBJD. The requirements of the programcomprehensively address all the majorroutes of transmission of BJD. Theprogram is audited and administeredon-farm by approved private veterinarians.In 2003 JDCAP was made a mandatorycomponent of the Victorian Test andControl Program (TCP).16 Dairy farm guidelines for BJD control

Part 3. Frequently Asked QuestionsVictorian Test and ControlProgram (TCP)The Victorian Department of PrimaryIndustries (DPI) currently offers a voluntaryBJD test and control program to infectedVictorian dairy herds. The program isadministered by DPI and includes a subsidyfor annual blood testing, a requirement toimplement a hygienic calf rearing program(called JDCAP), limited compensation forblood test positive cattle and managementby a private vet. The program has beensuccessful in reducing the incidence ofclinical disease within infected dairy herds.For more information contact your localDPI Victoria district veterinarian.Beef OnlyBeef Only is a market assurance programfor beef cattle to provide assurance thatthey are low risk of BJD. Beef Only cattleare beef cattle that have minimal contactwith dairy cattle and have not grazedpasture that previously was used torun adult dairy cattle.CattleMAPThe Australia Johne’s Disease MarketAssurance Program for Cattle (CattleMAP)is a voluntary, industry-driven, nationalprogram to identify, protect and promoteherds that have a low risk of being infectedwith BJD. It is a test-negative program withassurance levels based on the number ofnegative tests a herd has had.Question 5How can BJD contaminatedland be managed?Key pointsBJD bacteria can survive for longperiods (up to one year) in theenvironment under ideal conditionsBacterial survival is enhanced in shadedenvironments where temperaturefluctuations are moderated.Moisture is not required for survival,but low-lying areas (that may be moistor boggy) accumulate contaminationand could be potential hot spots.Options for contaminated landmanagement include:− leave land vacant for at least12 months;− graze species not susceptibleto BJD for 12 months;− graze young cattle destined forslaughter at less than 24 months;− grow crops on the land;− graze only adult cows (>12 months)but do not calve cows on the land;− fence off low-lying areas andmanage watering points.18 Dairy farm guidelines for BJD control

Part 3. Frequently Asked QuestionsQuestion 6Can BJD be spread by semenand embryos?Key pointsThe risk of spreading BJD throughsemen from infected bulls is low.BJD bacteria may be present in semenof infected bulls and this risk is greaterin clinically infected bulls.Bulls are routinely screened for BJDprior to collection of semen in AI centres.Embryo transfer is an effective methodof preventing transmission of BJD frominfected donors.Embryo recipients should be sourcedfrom low-risk herds.Question 7Does early calf removal affectthe welfare of the cow or calf?Key pointsEarly calf removal has little or no impacton the welfare of the cow or calf.Separating calves from their mothersmore than 12 hours after birth is morelikely to induce signs of maternal stresssuch as ‘mooing’.Cattle are highly sociable animals andkeeping young stock separate fromadults has no measurable impacton welfare.If animals are sick, their welfare isadversely affected. The dairy industryhas an ethical responsibility to minimisedisease in livestock and so implementcalf programs to manage BJD.Question 8Can floods spread BJD?Key pointsBJD bacteria can survive in soil andwater for up to 12 months.Heavy rainfall, leading to floodingof dairying regions, can disrupt dailyfarm routines, and result in waterand sediment deposits remainingfor prolonged periods.Flood water is likely to contain verylow concentrations of BJD bacteria socalves drinking flood water represent alow risk of contracting BJD.Sediment may contain concentrationsof the bacteria so grazing cattle lessthan 12 months of age on these areasshould be avoided.Priority should be given to ensuringcalves are not exposed to flood watersediment or effluent from adult cattle.Disrupted boundary fences presentrisks with the mixing of young stockwith adults.Dairy farm guidelines for BJD control 19

Part 3. Frequently Asked QuestionsQuestion 9BJD and milk qualityassurance: what arethe issues?Key pointsThe suggestion that there is a linkbetween BJD and Crohn’s diseasehas been around for decades andcontinues to be thoroughly investigatedby the medical community.The specific cause or causes of Crohn’sdisease have not been identified.Several scientific papers investigating apotential link between BJD and Crohn’sdisease are published each year,however the current evidence does notsupport a causal link between BJD andCrohn’s disease.Pasteurisation is highly effective inkilling the BJD bacteria.Question 10How useful are thediagnostic tests for BJD?Key pointsImminent clinical cases are readilydetected by the blood ELISA test.The closer an animal is to being clinical,the more likely the blood test will give apositive result.Faecal culture is slow but a positiveresult is definitive.High-risk groups of cattle can beidentified following a whole herd test.20 Dairy farm guidelines for BJD control

Dairy AustraliaABN 60 105 227 987Level 5, IBM Centre60 City RdSouthbank Victoria 3006 AustraliaT + 61 3 9694 3777F + 61 3 9694 3733E bjd@dairyaustralia.com.auwww.dairyaustralia.com.auMemberline 1800 004 377

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