What’s new in mastitis – the 34th British Mastitis Conference

From its small beginnings in 1978, the British Mastitis Conference has developed year by year, and the climate for milk production has changed greatly. It was in 1978 that there was talk of a “milk lake”, and farmers were paid to transfer from dairy to beef production. Many farms also stopped milking because of the costs involved in changing from churn collection to bulk tanks, and milk quotas were yet to be introduced. Payment according to cell count was for the future, and the use of dry cow therapy for all cows, linked to hygiene and calving management, was still a fresh idea.

Milking clothes were also commonplace in the many abreast parlours. Automatic milk cluster removal was a “new thing”, and over-milking was considered a prime cause of teat end damage and subsequent infection entry. The Milk Marketing Board was the go-to reference for the interpretation of new developments, and the National Institute for Research in Dairying provided a solid understanding of all things to do with milk extraction.

One might imagine that over 40 years later, there would be little that has not been thrashed out, but not a bit of it.

Forty years later

Boluses and other treatment options

With the thrust to reduce the use of antibiotics, boluses are being sold to farmers containing garlic and other mixes. These boluses are being administered for mastitis treatment in large quantities at considerable cost and are being attributed with effectiveness on farms also engaging with their veterinary practice. For many delegates, this was seen as an under-the-counter activity and led to much discussion over lunch. Jude Roberts (Map of Ag) included boluses in her presentation on alternative therapies.

Boluses are being administered for mastitis treatment in large quantities at considerable cost and are being attributed with effectiveness on farms also engaging with their veterinary practice

Also discussed were:

• immuno-regulators as replacements for dry cow therapy and teat sealants (not yet on the market)
• bacteriophages as treatment
• endolysins for staphylococci
• antimicrobial peptides
• lactic acid bacteria to reduce the colonisation of teats
• nanoparticles
• stem cell therapy
• protein factors
• acoustic pulse therapy
• vaccines

The point was made that it is important to monitor responses to therapy. It is also well recognised that many cows self-cure.

Independent milking machines

John Baines (Milking Equipment Association) gave a detailed account of independent milking machine tests on 103 new installations. Sixty-nine percent of the installations were satisfactory for vacuum and milk system leakage, and 68 percent were satisfactory for vacuum regulation. Roughly one-third of new installations were not operating to the manufacturers’ specifications. In most cases, the machines are not installed by the manufacturers but by agents.

It is felt that milking efficiency and udder health have improved since surveys in 1997 and 2007, but there is a need for independent testing of installations, and enhanced training and education are seen as important moving forward.

Dairy herd operating environments

Ian Ohnstad highlighted that the operating environment for dairy herds is changing. He referred to figures indicating that 63 percent of dairy herds are struggling to recruit staff, 31 percent of dairy farm staff stay in post for more than five years and 42 percent of dairy farmers employ overseas labour.

Three surveys in 2021 indicated that a herd expects to have 30 cases per 100 cows treated for clinical mastitis each year. Studies have shown that a single teat spray at the end of milking achieves 50 percent teat coverage, whereas two short bursts of spray achieve 89 percent. Trimming the tails allows spray to cover the teats better, with 95 percent of teats and 89 percent of teat barrels sprayed with 30ml of product.

Three surveys in 2021 indicated that a herd expects to have 30 cases per 100 cows treated for clinical mastitis each year

In consideration of ways to improve milking efficiency, vented liners allow the vacuum level at the teat end to remain constant, with a general improvement in cow comfort and fewer teat end contusions. Vacuum control for the individual cow steps up the vacuum with higher milk flow; as the flow drops, the vacuum falls. This achieves faster milking by extracting the milk at peak flow more quickly. Poor cluster presentation is, however, an issue, and a cluster support device reduces liner slip and unit kick-offs.

AHDB Mastitis Control Plan – a case study

Katie Fitzgerald (Bishopton Veterinary Group) gave her account of applying the AHDB Mastitis Control Plan with a herd of 750 high-yielding Holsteins. The herd was milked three times a day and had a somatic cell count of 130,000 and 39 cases of mastitis per 100 cows, with 7 percent of the group considered chronic cases. Genomic selection was used to select replacements and a 305-day yield of 11,500 litres was achieved. The work to operate the control plan was handled separately from other veterinary activity at the farm.

There was less than one cubicle per cow with damaged cubicles – Katie considers that the farmer is “asking the building to work hard”. Overstocking led to “much muck” and fresh-air-seeking behaviour from the cows, and there was noticeable wear and tear on the water troughs, requiring frequent maintenance. With the high number of cows, it was a long milking shift for the workers and 23 people were involved in milking the cows. Low-yield cows received less attention with poorer housing – these cows were considered a major source of mastitis for the herd.

Trying to move forward is an interesting task but the staff responded well to having videos taken of them at work. This approach led to good engagement and discussion over tea and biscuits in the staff room.

The impact of milk prices

Kathryn Rowland (Kingshay) discussed the impact of milk price on mastitis costs and herd performance, and her poster was awarded the annual trophy. The cost of a clinical case of mastitis is calculated to be £200 at 25p/litre and £400 at 50p/litre. A dairy costings focus is available to download from Kingshay. A yearly incidence of 30 cases per 100 cows currently costs the farmer £10,000 – an increase from the £7,500 indicated in 2021. The range of milk prices, seen in September 2022, for the farms involved was from 44p/litre to 54p/litre. Mastitis accounted for 9 percent of the reasons for culling and infertility 14 percent. Overall, 29 percent of cows are leaving herds each year, and milk price influences culling decisions.

Data collection and analysis

Clare Cubby (University of Limerick) reported the results of a study investigating the somatic cell count of herds at the first milk recording of a lactation. Findings suggest that herds administered teat sealant alone have a higher cell count than those using selective dry cow therapy and teat sealant together. It was also indicated that herds whose cubicles were cleaned twice a day had lower cell counts than herds with once-a-day cleaning. This was also true for those herds with more than one cubicle per cow, where cows were stripped before milking, where clinical mastitis was recorded and when the California Milk Test was used.

Robust analysis is best achieved when all clinical cases of mastitis are recorded and a representative population of cows is sampled within the first 30 days in milk

Al Manning (Quality Milk Management Services) discussed the Mastitis Pattern Analysis Tool, which has been developed with herds carrying out monthly milk recording to provide an automated diagnosis of the predominant route of infection. He presented a study carried out with herds that have less frequent milk recording and found that Mastitis Pattern Analysis is still possible. However, robust analysis is best achieved when all clinical cases of mastitis are recorded and a representative population of cows is sampled within the first 30 days in milk. Reducing the frequency of milk recording led to an apparent increase in the lactation new infection rate and a decrease in the apparent prevalence of chronically infected cows.

On-farm diagnostics

Michael Farre (SEGES Innovation Denmark) has worked with farmers to achieve the best practice with on-farm diagnostics for mastitis. With laboratory-based diagnostics, the treatment can be finished before microbiology is completed. Cross-checking samples tested by veterinary practice laboratories found that only half of the practices achieved the correct bacterial identification with 50 percent of the samples.

On-farm tests help motivate and engage staff with the control of mastitis, but continuous monitoring of procedures is required by the farm vet. However, farmers often have the impression that diagnostics are an expensive procedure. The role of colour change tubes is to help the farmer to decide whether to treat or not; however, experience indicates that the farmer likes to decide on the testing system, so two are offered for the farmer to choose from. Training is provided so that one person is available to test at each milking.

With moderate mastitis showing changes to the milk and local clinical signs, no effect on outcome is recorded if treatment is delayed for 24 hours. Gram-negative and culture-negative samples are likely to result in self-cure. It is important that quality assurance is achieved with samples regularly sent to a laboratory for verification.

Final thoughts

Simon Archer (University of Surrey, School of Veterinary Medicine) highlighted that, in deciding on management changes for mastitis, it is important to question available evidence. Effective decision making is believed to depend on luck in the short term and good judgement in the long term. Simon states that “the only certainty is that evidence is uncertain”.