ONE of the features of the British Mastitis Conference is the small sub-group discussions taking place throughout.
The previous day saw the inaugural meeting of the European Mastitis Research Workers and many of the international participants joined the conference.
This provided an opportunity for discussions between researchers and the many veterinary surgeons attending about mastitis management in the field. It is the conversion of research to impact on the ground that raises the greatest interest among the delegates.
Sixteen poster presentations were reviewed and voted upon. Pre-selected to give 20-minute reviews of their projects were Dimitri Valckenier (Ghent University) who described the beneficial effect of coagulase-negative staphylococci on first lactation heifers, Karin Persson Waller (National Veterinary Institute, Sweden) reported on the variation in veterinary surgeon treatments for clinical mastitis, and Karlien Supre (Flanders Milk Control Centre) outlined the efforts to develop a responsible use of antimicrobials without loss of good udder health.
The best poster award went to a group from the University of Nottingham, led by Virginia Sherwin, studying the prevalence of Streptococcus uberis in the faeces of dairy cows within one 250-cow herd.
The percentage of cows shedding the organism ranged from 10%, when on pasture, to 33% when in winter housing. The turnout of cows onto pasture is expected to reduce shedding. Fat cows (body condition score of 3.5 or above) have an increased incidence of shedding, as do early lactation cows and heifers.
Work is ongoing to confirm that shedding faecal Strep. uberis causes clinical mastitis in the same cow and a key question is where in the gut is the organism located. DNA was extracted from rectal swabs and specific genes were identified. Any relationship between previous shedding and later shedding is being correlated.
Strain typing
Professor Jamie Leigh (University of Nottingham) reviewed the role of strain typing for Strep. uberis. The management of mastitis is directed at particular pathogens and their identification is of considerable bene t. Examples are Strep. agalactiae indicating cow to-cow infection and E. coli contamination from the environment.
The identification of specific bacterial strains (de ned sub-species groups) may assist in the development of more effective control measures. Strep. uberis is not effectively controlled by routine implementation of the five-point plan, suggesting that it is largely transmitted to the milking gland by an environmental route. The outcome for the cow of becoming infected ranges from a transient sub-clinical infection to an acute severe clinical mastitis.
Applying Multi Locus Sequence Typing (MLST), the genetic variation and evolutionary relationships can be identified. A study of 52 herds has shown that 40% of clinical cases were due to infection with a very limited subset of largely related strains. These nine strain types were found in many herds but of the 195 identified, in total 148 were found in a single herd.
No animal appears to be permanently colonised by Strep. uberis and a good proportion of animals appear never to be colonised. Identifying whether individual cows shed single or multiple strains of the organism in their faeces and whether these strains are found in the mammary gland offers the opportunity to focus control measures at critical points in transmission of this pathogen. There is potential for disease control within the mammary gland and external herd management factors.
Cheesemaking
Attention to detail in all areas of milk production was the overriding impression given by Mary Quicke (J. G. Quicke and partners, Devon) in her assessment of the importance of milk quality in producing world-class cheese consistently.
The farm makes around 200 tonnes per year of traditional cloth-bound cheddar cheese from the milk of a 500 cross bred herd. The whole cheesemaking environment, from the management of the cows to the skill of the cheesemaker, influences the flavour and balance of the cheese. Consistency is vitally important.
The full paper is in the proceedings and covers over 20 important considerations. These include: less than 25% of the milk for cheese needs to be from late lactation cows and management of fertility and calving is critical; cheese moisture drives maturing – mastitic and high cell count cows have higher moisture milk; beneficial teat micro flora are encouraged, no teat washing, manage cubicles for clean cows and fresh feed immediately after milking to keep cows standing; relaxed cows, no whistling or shouting; clipped tails and singed udders; investigate if over one case of clinical mastitis in a month; high cell count milk delays cheese starter culture growth, inhibits acid production and delays fermentation.
The final outcome is the grading when the quality and flavour of the cheese are forecast many months ahead. It is at that point that the effectiveness of the earlier work is recognised.
Kirsten Reyher (University of Bristol) is involved in the development of a training package for veterinary surgeons to improve the uptake of veterinary advice.
“Motivational Interviewing” has been studied and the indications are that not only would its application improve a veterinarian’s ability to engage clients with change, but also empower farmers to utilise their own knowledge and motivations. Veterinary practices are invited to participate in the programme.
Machines failing
One of the fundamentals of mastitis control over many years has been the influence of the milking machine. Elizabeth Berry has prepared data from Genus indicating that 59% of milking machines are still failing the test, although this is an improvement from 10 years ago (81%).
The number of herds has declined from 17,415 (2004) to 11,477 (2014). Insufficient vacuum reserve was recorded with 10% of parlours and 47% had excessive vacuum leakage. The data are a reminder that it is important to check the proven basic elements for the control of mastitis.
Mastitis advice
Keith Baxter (Westpoint Veterinary Group) discussed the delivery of mastitis control advice at farm level. A problem farm is identified as follows: rolling bulk cell count over 200,000 cells/ml; milk quality payment penalty deductions; over 35 cases of clinical mastitis per 100 cows, more than one in 12 early lactation cows with clinical mastitis; stringent farm assurance requirements.
Any one of these is considered a veterinary intervention opportunity for the practice and a potential benefit for the client.
The use of antimicrobials is a current issue of importance. Certain infections, such as coliforms and coagulase negative staphylococci, may not be influenced by treatment with antibiotics. Increasing interest in on-farm diagnostics allows farm staff to either use narrow spectrum antibiotics or just treat clinical signs with non-steroidal anti-inflammatory medication.
A treatment strategy for routine clinical cases, sick and toxic cases, recurrent cases and dry cow mastitis forms part of the herd protocol. Selective dry cow therapy and teat sealants are becoming the norm. Investigating the milking process, the milking machine and management of the environment may require some subterfuge on behalf of an investigator, as farm staff often put on their best behaviour for occasional visitors. The veterinary surgeon has to understand the real activities on the farm.
Changes in NZ
Eric Hillerton (New Zealand) outlined the changes facing dairy farmers in his country. Although the milk price is currently below the cost of production, the standards for milk are becoming more stringent.
Milk buyers are operating to below the level of detection for residues and not the legal requirements. Previously accepted products are being withdrawn and substitutes sought. Teat sealant reformulation is expected to eliminate the risk of black spot in cheddar cheese.
The NZ Veterinary Association has an aspirational statement that “by 2030 New Zealand Inc will not need antibiotics for the maintenance of animal health and wellness”. Immune modulation, immune enhancement and genetic resistance are included in the ways forward. The criteria for each cow at drying off will be cull, treat, seal or nothing. The cost of veterinary advice is expected to match any cost saving.
A final thought is that the recent relaxation of birth control in China may lead to 100 million more babies requiring infant formula. New Zealanders are poised to serve that market.
