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Considerations when tackling mastitis in cows

Vets were urged to consider how best to develop a structured approach to mastitis with clients

26 March 2020, at 9:00am

The 31st British Mastitis Conference attracted some 25 veterinary surgeons from practice, who shared their knowledge and awareness with industry and academia. The event is organised by The Dairy Group, the British Cattle Veterinary Association, Quality Milk Management Services Ltd and the University of Nottingham. One of the features of this event is the high quality of poster presentations from the UK and overseas and four of the authors are invited to present their work as part of the main timetable of events. The speakers and poster presenters gather for general discussion in the centre of the hall and delegates have time during lunch to translate what is offered into their own practical requirements. Each year more detailed and original information becomes available and the British Mastitis Conference provides the opportunity to gather the latest ideas in an informal setting. The contact details for authors and speakers are within the proceedings so that follow-up is available and encouraged. Copies of the proceedings are available from The Dairy Group. The event is sponsored by Vetoquinol, Boehringer Ingelheim, Hipra, MSD, Milkrite, Zoetis and Ambic.

Colin Mason, SRUC Veterinary Services, discussed the importance of Mycoplasma bovis as a mastitis vector. A common clinical sign is that cases do not respond well to treatment. The organism does not have a cell wall so β-lactam antibiotics are ineffective, neither does it synthesise folic acid so sulphonamides are ineffective. The organism is susceptible to antibiotics that interfere with protein or DNA synthesis including tetracyclines, macrolides, lincosamides, florfenicol and fluoroquinolones. The need for accurate diagnosis is evident if high priority critically important antibiotics are to be selected. Sensitivity testing cannot easily be carried out in diagnostic laboratories or veterinary practices. Minimum inhibitory concentration testing is available and the cost justifiable. The speaker highlighted that increasing antibiotic resistance has been indicated.

Clinical cases are sporadic but one 350-cow herd with a history of low cell count and low incidence of clinical mastitis had cows with swollen fetlocks and joints, an increase in clinical mastitis and raised cell count. Some cows had leg problems, some mastitis and some both. Twenty-six cows were treated for arthritis with NSAIDs, oxytetracycline and tylosin, with variable results, and four were culled. A compulsory control programme is operating in New Zealand with 201 confirmed properties (Biosec New Zealand). Bulk tank PCR and serology testing offer options for assessing herd status but more than 30 percent of cows in a herd need to be infected for the bulk sample to show positive. There are no vaccines licensed in the UK.

Biosecurity of the herd is paramount, with strict controls and quarantine of purchased animals and suspect clinical cases. The milking order of cows from low to high risk should be implemented and hygiene in the milking parlour, with control of fomite spread, is essential. As well as cow-to-cow contact and spread of the organism via the milking machine and directly by handling teats and udders, there is a risk from a shared airspace and transmission nasally. Pasteurisation of milk is effective and it is essential that waste milk from treated animals is not fed to calves.

Ian Ohnstad of The Dairy Group presented a practical awareness of the effective use of the milking machine that can be utilised without involving complicated and expensive equipment. For veterinary surgeons in practice a copy of the paper as reference would be worthwhile. Ian concluded that “it is not sufficient to consider the operation of the milking system based on physical tests without the interaction of the milker and the cows”. It is important to be aware that an evaluation of the milking system, without taking account of the animals and the operator, is likely to lead to a system being described as satisfactory when this is far from the case. The following aspects may prove useful for veterinary investigation.

The presence of palpable mouthpiece rings on more than 20 percent of teats indicates problems with vacuum levels in the liner mouthpiece chamber, with incomplete collapse of the liner around the teat end. There is an association between circulatory impairment and new infection rates. No more than 5 percent of cows should exhibit liner slippage. If an increase is noted then it is important to establish whether it is due to individual cows with poor udder confirmation or a general problem throughout the herd. Once the milking unit is attached the automatic cluster removal (ACR) cord should be fully extended and the milking unit hanging squarely below the udder, with even weight distribution on all four teats. Experience shows that over 10 percent of clusters are poorly presented to the cow. Problems with ACR settings and unit positioning can leave milk in the udder. When hand stripped after milking a quarter should yield less than 100mL of milk.

It was established that cleanliness of the milking environment and the operator is important for the production of high-quality milk. Examination of areas in contact with hands, such as keypads, can highlight hygiene issues. Agitated cows in the collecting yard release adrenaline that can interfere with milk let-down and prolong milking. Calm cows do not generally defecate and if more than 5 percent of cows defecate during milking, change is indicated to allow cows to enter and leave the milking facility in a calm manner. Teats should be clean and dry prior to unit attachment and it can be informative to wipe teats with a moist white towel post-preparation. Dirty cows are three to four times more likely to have higher infection levels. Scoring teat condition on a regular basis includes teat end hyperkeratosis, teat oedema and congestion, teat colour and the presence of palpable teat base rings. A teat condition portfolio chart is available from the National Mastitis Council. Less than 20 percent of teats should have rough or very rough teat ends.

James Breen, University of Nottingham, and Austin Russell, Church Farm Cirencester, discussed the implementation of the AHDB Mastitis Control Plan. Applying the AHDB Dairy Mastitis Pattern Analysis Tool, the herd mastitis pattern was one of environmental infections of dry period origin with lactating period origin infections associated with periods at pasture. Changes on-farm included a review of drying off technique, the availability of loafing and feed space, improving ventilation and managing the aspiration to move away from loose yards to housing dry cows in cubicles. Over two years, the dry period new infection rate has decreased from 21.6 percent to 11.4 percent and the incidence of clinical mastitis from 64 to 47 cases per 100 cows per year. A start has been made to manage antimicrobial use with a reduction from eight to six defined daily doses. The authors of the comprehensive paper conclude that the structured approach to mastitis control provides a platform for future progress. In discussion it was pointed out that no quick fixes were anticipated and that part of the role of the advisor is to manage the expectations of the farmer.

The best poster was voted on by the delegates and awarded to Derek Armstrong on behalf of a technical group involving AHDB, University of Nottingham and QMMS Ltd, outlining the QuarterPRO initiative. The farm team is encouraged to sit down with the farm vet and advisors, once a quarter, to review what has been happening with mastitis on the farm. The Mastitis Pattern Analysis Tool is available to predict the most important udder health issues on-farm in the next quarter. The PRO in the title is to “Predict” the mastitis activity, to “React” and decide what changes to make and who will make them and to “Optimise” udder health on the farm. The aim is for continuous improvement. Implementing QuarterPRO will meet the new requirements of the Red Tractor Dairy Standards.