The Interview – Dr Eric Hillerton, New Zealand

Dr Eric Hillerton (now in semi-retirement) had a long career in the dairy industry and led research on mastitis, developments in milking technology, automated milking systems, milking frequency and milk quality.

M2 magazine asked Dr Hillerton to highlight the stand-out work in his career.  He picked up on two subjects

• how the Five-Point Plan to control mastitis on dairy farms was developed and implemented; and
• the science surrounding modern-day teat dips.

 

M2 magazine: So, how did the Five-Point Plan for mastitis control develop?

Dr Hillerton: I will reference a paper I gave with Dr James M Booth to a meeting of the National Mastitis Council (NMC) in 2018. In it we described how the Five-point mastitis control plan was developed and implemented and showed the success of the plan over the course of almost 50 years since it’s launch. Even to-day, the application of the plan on dairy farms remains essential for good udder health in dairy cows.

 

M2 Magazine: What were the origins of the plan?

Dr Hillerton: The story of the plan is about great thinking by imaginative scientists, technical innovation by researchers and the dairy industry, good applied science to test and trial in the real world of dairy farming, and creativity in selling to and engaging with farmers.

In summary, the plan came from innovative British research; it followed a loose term originated in Australia; the evolution of the plan into five points was by the Milk Marketing Board (MMB) for practical application to farmers in the UK; in New Zealand, the Kiwis launched a bold and imaginative extension project; and successful adoption has been enjoyed by British, New Zealand, Australian and US dairy farmers and by many others; and, of course, by their dairy cows.

 

M2 magazine: So, the plan and it’s early development.

Dr Hillerton: In the early days, mastitis field experiments initially centred around teat disinfection; then developed further with better teat disinfectants and emollients. The results were encouraging but the trials revealed some difficulties. In particular, in applying the plan on-farm in real-time and on farms that, in the main, were relatively uncontrolled and unsupervised and where there were few obvious incentives to implement the plan and improve milk quality.

Researchers found that neither veterinarians nor advisors ever have enough time on farm to provide adequate supervision, therefore farmers had to be properly and continuously motivated to adhere to the mastitis control plan on offer.

 

M2 magazine: What were the components of the plan?

Dr Hillerton: The plan centered on five components. It must be emphasized that a scrutiny of the findings shows that it is important the plan is applied in the order set out and no other.

1. The milking machine. The early mastitis field experiments did not test the role of the milking machine but set minimum operating requirements; requirements that are now far exceeded by today’s standards.

The trials with UK farmers required that the proper operation of the milking machine was the starting point to remove any risk from the milking process and because results were positive, farmers became more receptive to further advice.

Thus, the first point is proper machine testing and maintenance. In the 1970s only 29% of farms in the UK reported having their machine checked annually. It is regrettable that despite much better milking machines today, dairy farmers still fail to remedy machine defects identified by testing with a recent survey showing that 60% of machines are not meeting operational requirements.

2. Teat disinfection. Disinfecting every teat of every cow after every milking is a core requirement but is the most variable as regards means and quality of application; and requires the use of a quality product.

Consistent use is often affected by lack of time, operator stress and farm economics. In the 1970s only 35% of farms teat dipped after milking. And 30% of those withdrawing from the MMB trial did so because teat dipping was too difficult. The initial New Zealand attempt at the program did only a little better despite their supposed saving of staff time by spraying the disinfectant onto the teats.

3. Lactation therapy. This depends on detection and an appropriate treatment, according to the likely pathogen. Initially, getting the attention of veterinarians and veterinary authorities was not easy. The role of the farm veterinarians was always crucial and remains so to-day as they are the source of proper advice and of all prescription medicines.
4. Dry period protection. The need for dry period therapeutic elimination has always been a crucial component but is now less so. The need to prevent new infections in the dry period remains mandatory but does not necessarily require antibiotic use.
5. Culling. The need to get rid of the persistently mastitic cow persists. In many cases there is now more opportunity to cull on udder health, as fewer cows need to be removed from the herd for other health reasons.

 

M2 magazine: And did the plan work?

Dr Hillerton: Many studies and reports have shown the effectiveness of the Five-point plan. Whilst it is applied at herd level the benefits are obvious at national levels.

Let me give two examples. First, the improvement in udder health of dairy cows in the UK as measured by national cell count (where the National Mastitis Awareness Campaign was pursued with vigor, particularly by cattle veterinarians). National cell count data for England and Wales showed cell counts in the range 500,000 to 600,000 per mL from 1971 to 1974 and falling to 150,000 to 200,000 per mL from 1997 to 1999.

Second, when the National Institute for Research in Dairying (NIRD) at Reading closed in 1985, the successor group moved to (what became) the Institute for Animal Health at Compton and inherited a research herd, the Chesridge herd, with, to put it politely, less than perfect mastitis management.

Good application of the Five-point plan led to the elimination of Staph. aureus infections and minimal clinical mastitis by contagious pathogens. This was despite the best attempts of various scientists to create infection by experiments in pathology, immunology and milking machine investigations, and trials including testing teat disinfections! In the herd, clinical cases of mastitis were at 150 cases per 100 cows in the 1960s. By the late 1980s and in the 1990s, cases had fallen to 40 cases per 100 cows.

All the examples available show how well the Five-point plan works, and they show that the effects are incremental over time. I stress that persistence with mastitis management on farms is essential.

 

M2 magazine: So, in a paragraph, how would you summarise?

Dr Hillerton: On the dairy farm, the farmer and farm staff must want to manage mastitis risk and reduce the levels of mastitis in their herd.

To maximize adoption of the plan there must be an understanding of the issues, education in the aims and outcomes of the plan, and a full realization that benefits do not accrue in days or weeks but in years. The farmer needs training, motivation and above all, patience.

 

M2 magazine: Your second major interest is teat disinfectants – why so important?

Dr Hillerton: The teat and the teat canal are central in the battle against infections, in particular infections resulting in mastitis. So the work required to clean and disinfect teats and the science involved in the development of disinfectants are of vital importance. I will reference a paper I presented with Mario López at the British Mastitis conference in 2018.

 

M2 magazine: So, what are the ingredients in a teat dip?

Dr Hillerton: Modern teat disinfectants are complex formulations designed to accomplish a number of tasks. A good teat disinfectant has to kill bacteria quickly; spread over the skin easily; and ensure the teat skin is healthy, soft and undamaged.

Modern disinfectants have a formulation that can be sprayed as well as dipped. The aim is to ensure good skin coverage as soon as possible after milking is finished.

Manufacturers of teat disinfectants play a major role in developing and commercialising pre- and post-milking products that meet producer needs, but that are also well aligned with market and regulatory requirements.

 

M2 magazine. So, what is the background to their development?

Dr Hillerton: We are constantly reminded of the fast-paced, evolving environment that we live in.  Some dairy farmers are milking bigger cows that yield more milk than ever before, others are milking more cows, and we are all trying to harvest the milk in the fastest way possible, using either manual or automated means.

Efficient use of labour is now vital, often because skilled help is harder to find. All that, and we also expect our cows to remain healthy for the largest number of lactations possible.  Moreover, if these cows get sick, we want to make sure we reduce (or nullify if possible) the usage of antibiotics – as consumers consistently demand of livestock products in a growing number of countries. In terms of mastitis prevention, usage of an effective teat disinfectant product, applied in the most appropriate way and at the correct time, is essential.

 

M2 magazine. Where did it all start?

Dr Hillerton. In a series of experiments conducted by Frank Neave and the mastitis team at NIRD in 1962, it was clearly shown that the amount of teat end contamination by bacteria is directly related to the risk of an intra-mammary infection  (IMI), effectively a direct correlation between the numbers of mastitis-causing bacteria and expected IMI.

Getting teats clean and reducing the numbers of bacteria involved in mastitis that occur on and in teat skin has remained an essential part of achieving a healthy udder and good quality milk ever since.

In essence, a teat disinfectant is composed mainly of three things:

1. a) a germicidal component for killing microorganisms; b) an emollient package for maintaining good teat skin health; and c) a surfactant element for better coverage on teat skin and for improved removal of soiling material like faeces.

Water makes up the majority of the formula and the importance of the chemical and physical properties of that water, especially its quality when the disinfectant is prepared on–farm from a concentrate, must be appreciated.

 

M2 magazine. So, could we look at each component in turn?

Dr Hillerton.

Germicidal components. A disinfecting solution applied to teats when the cow had finished milking was the first really successful attempt at preventing mastitis in cows.  Pine oil was first used in 1916, and years later a dilute solution of sodium hypochlorite (bleach) became the germicide of choice. Simple iodine formulations were introduced in the 1960s.

Many different germicides have been suggested and tested over time, but only a few have become solid commercial candidates due to market acceptability and regulatory demands that focus increasingly on efficacy and preventing contamination of milk and its products.

Examples of germicides include: hydrogen peroxide, but is not allowed in some countries as it has been used to ‘clean’ bulk milk because it is largely undetectable. DDBSA (dodecylbenzenesulfonic acid) is not so common now as a post-milking product as it is akin to a swimming pool disinfectant and can result in residues. Chlorhexidine, an older technology is still very common in many countries, but is being challenged due to its use in human medical hygiene; and more modern disinfectants that use chlorine dioxide or lactic acid or glycolic acid.

Iodine is still the preferred germicide in most countries. The early formulations, being extremely acidic, were harsh skin irritants. The modern formulations are closer to a neutral pH and so are milder on skin, but they also have enhanced killing power as they liberate more free iodine at a lower overall iodine content.

The emollient package. A fundamental outcome of the early Neave work was that of ensuring intact and healthy teat skin. Preventing chapping of teat skin was critical in minimising mastitis-causing bacteria, especially Staph. aureus and Strep. dysgalactiae.  In experimental studies, intentional chapping of teats with sodium hydroxide caused aggressive dryness to skin, and teats that were more likely to support colonisation of Staph. aureus.  Faster healing and lower bacterial colonisation of these teats was observed when they were dipped in solutions with emollients.

The emollient package is associated with maintaining good teat health and preventing skin dryness, but overall, it is the formula that has a beneficial or adverse effect on teat skin health.  A 5% glycerine teat disinfectant was used on two automatic milking system farms that had not used any product for more than a year.  The result was that within two weeks, optimal condition of both the teat barrel skin and the teat end was achieved, becoming more than 2.2 times greater than initial values.

In practice, emollients make more sense when applied post-milking than before milking because of the longer contact time.  Typically, emollient levels in post-milking teat disinfectants do not exceed 10%, unless they are a formulation available in some countries to cope with extreme winter conditions, the winter dips.

Teat condition evaluation is important to guarantee the safety of products on teat skin and we recommend that this be done regularly to establish the teat skin condition of the herd, set goals, and take action to meet them. In well-managed herds that have milking machines in proper working order and use well tested products, a teat condition score of 1 (optimal teat skin) should be evident in 90% to 95% of quarters.

Surfactant elements. Surfactants are molecules that play various roles within a teat disinfectant formulation, such as a detergent (helps to remove soil from the skin), a solubilising agent (complexing agent in iodophores), a foaming agent, or an emulsifying agent. For cleaning purposes, by helping to reduce the tension between the liquid solution and the skin, better penetration of the product into the immediate skin surface is achieved, leading to better removal of anything soiling the skin.

Teat disinfectants with cleaning claims (especially for the pre-milking routine) should have a surface tension lower than water, and this will be evident in the success of cleaning compared with water alone. It has been shown that a properly formulated surfactant-based product was approximately five times more likely to clean dirty teats (scores 3 and 4 in scale of 1-4) compared to water alone.

Another interesting property of surfactants is their wetting ability. By lowering the surface tension of the liquid, the product achieves better coverage on skin when dipped or sprayed onto teats. This is the same action seen in plant sprays to get whole leaf coverage from droplets and is why these disinfectants can be sprayed onto teats successfully.

 

M2 magazine. You have covered post-milking applications; what about teat preparation prior to milking?

Dr Hillerton. Yes, pre-milking teat preparation is arguably one of the most important activities in the whole milking routine. Handling of teats stimulates release of oxytocin to ensure milk let-down, fore-stripping helps to identify abnormal milk and application of a pre-milking product aids in the reduction of bacteria on teats.

Depending on the germicide present in the pre-milking disinfectant, use of a pre-dip was 1.2 to 4.5 times more likely to reduce Staph. aureus and Strep. spp. counts compared with washing and drying alone.  Results from pre-milking disinfection are more variable between farms but when any farm has a mastitis problem the use of any good disinfectant product will be beneficial.

 

M2 magazine. Dip or spray?

Dr Hillerton. Mostly we talk about teat dipping and this remains the most common means of applying a disinfectant in small herds.

However, when the parlour has a larger throughput or is labour-limited, e.g. large rotary parlours with only one person at cups-on position, automated means of disinfecting teats are needed.

Traditionally, spraying disinfectant was hit and/or miss, commonly in an exit race, and consumption with such systems was often two or three times the amount of disinfectant applied by dipping (up to 30 mL per cow per milking versus 4 mL to 10 mL)

Fortunately, efficient automated disinfection systems, very soon after cups-off, are now available and activated while the cow is still on the platform.

One system, in use on conventional and automated rotary milking farms, uses a single robotic arm.  Another, now found internationally, uses individual spray nozzles located below each teat whilst the cow is still in the milking position.

These systems solve one of the requirements of the earliest work on teat disinfection – do it as soon as the cluster comes off.

 

M2 magazine. So, to summarise

Dr Hillerton. In a nutshell

• Modern day teat disinfectants do more than kill bacteria on teats, still an essential function of any product used pre- and post-milking.
• Healthy and soft teat skin should be the target of the dairyman, and this is achieved by using products that are not harsh to skin and have an acceptable level of emollients.
• Surfactants play an important role in teat disinfectants, from complexing iodine, foaming properties and by improving teat coverage.
• The overall benefits of any well-formulated product can only be achieved if applied properly on teats, whether by manual or automated means.

 

Bio Dr Eric Hillerton

Dr Eric Hillerton lives in (semi) retirement in Cambridge in North Island, New Zealand.

Since his retirement as Chief Scientist at DairyNZ - New Zealand’s dairy industry on-farm research, development and extension organisation - he engages in consultancy work and is Adjunct Professor of Dairy Systems at Massey University.

Earlier, in his career in the UK, he was a Fellow at the University of Reading and Principal Scientist at the Biotechnology and Biological Sciences Research Council at Compton. Dr Hillerton holds BSc and PhD degrees from the University of Edinburgh.

Among many other positions he has been a national representative to the International Dairy Federation standing committees on animal health and farm management; has been a board member of the Johne’s Disease Research Consortium - a joint venture between industry and the science community in New Zealand; and has been president of the NMC in the USA. In 2020, Dr Hillerton received the NMC’s Award of Excellence.