17 Feb 2021
Phil Elkins
Job Title
The parlour should be clean enough to eat your lunch from.
As cattle vets we often forget that, as well as ensuring the health and welfare of stock under our control, we are also responsible for maintaining food safety and security.
The two are far from mutually exclusive, and this is clearly evident when discussing milk quality and hygiene. Vets can clearly influence the butterfat, protein and urea constituents of milk, but for the basis of this article, the emphasis is more on parameters that relate to udder health and hygiene, as summarised in Panel 1.
While control of these factors has been largely influenced by financial factors related to milk contracts, in many circumstances other benefits require control. However, in purely financial terms, the Agriculture and Horticulture Development Board (AHDB) estimates that failing to reach the best bands for somatic cell count (SCC) and bactoscan has cost dairy farmers £40 million a year (0.3 pence per litre) in milk payments alone (AHDB, 2020a).
SCCs are generally comprised of two distinct cell types – epithelial cells shed as part of the natural turnover of the lining of the mammary system and white blood cells produced as a response to foreign material (usually infection). Low somatic cell counts are rewarded in milk contracts, as somatic cells affect the longevity of dairy products, cheese making processes and, at the extreme end, taste. However, the maximum threshold for bulk tank somatic cell counts (often 200,000 cells/ml to 250,000 cells/ml) still represents lost income for a farmer.
The average yield for a cow with a SCC of 200,000 cells/ml (Hadrich et al, 2018) of milk is 6.8% lower than for a cow with a SCC of 100,000 cells/ml. A national herd SCC of 168,000 cells/ml (Hadrich et al, 2018) and a median proportion of the herd above 200,000 cells/ml (AHDB, 2020b) represents a significant loss of production through failure to control udder health. The 25% of herds with an average milk recording SCC above 221,000 cells/ml (Hanks and Kossaibati, 2018) also represent a significant loss to the dairy industry as a whole in longevity of product, processing ability and public confidence in the product (the so-called “pus in the milk” used by anti-animal agriculture activists).
The bactoscan is a measure of the number of bacteria, regardless of viability, in the milk. Similar to SCC, a high bactoscan has severe implications on the longevity of milk and dairy products, and in particular with the fermentation process used in production of yoghurt and cheese. Again, we have an important role in maintaining societal goodwill – is the presence of thousands of bacteria in one millilitre of a foodstuff acceptable? Current average bactoscans are 28,000 bacteria/ml, which may sit within many contracts’ premium bands, but represents many herds producing milk with too high a level of bacterial contamination.
These bacteria may have come from a number of sources:
The presence of medicinal residues, while not the focus of this article, is essential to mention as they have wide-reaching impacts:
Some excellent resources are available from both the BCVA and MilkSure to aid in preventing the presence of medicinal residues in milk.
Often, as vets, we are only called in to investigate these issues when the situation has become significantly worse and the financial costs are large. Involvement in milk hygiene and udder health represents a large opportunity for veterinary input and farm improvement, but benefits from a proactive approach. In many cases, vets have access to regular bulk tank sampling results tested through National Milk Laboratories (NML) via its associated software. If not, a simple request from the farmer can get these regularly sent to the vet directly from NML.
It is the author’s belief that the opportunity is there to use access to this information as a route to discussion; it may be a simple question at a routine visit, or a more concerted attempt to get involved. Often farmers are incredibly receptive to someone looking out for them, and two minutes spent checking the latest milk quality results prior to a farm visit can open up a new line of veterinary input.
Improving milk hygiene can take place by identifying issues throughout the milk harvesting chain:
Due to the implementation of the five-point plan, herd level contagious mastitis problems have become less common. Contagious pathogens, those whose primary reservoir is within the cow, are often responsible for mild to moderate increases in SCC, but with a prolonged persistence of increased SCC and low bacteriological self-cure rates.
Environmental mastitis is exactly that – infection of the udder as a result of pathogens whose primary reservoir is the environment. Typically, environmental pathogens are responsible for large rises in individual animal SCC. However, these often return to near normal relatively quickly. Environmental pathogens also have a relatively high self-cure rate.
When facing a high bulk tank SCC issue, it is impossible to differentiate between environmental and contagious behaviour of pathogens in the absence of at least one regular individual animal’s SCC analysis and the bacteriology of affected animals.
As SCC can only come from cows, a herd SCC that is higher than target must be a result of environmental pathogens, contagious pathogens or, in most cases, a combination of the two.
A multitude of published articles on differentiating between the two, as well as management factors, is available. For the purpose of this article, we will concentrate on only one aspect of control – cleanliness.
When considering the next two stages of the milk harvesting procedure – cow cleanliness and parlour cleanliness – it is important to remember the aim of a dairy farm: food production. By reframing milk harvesting into a food production setting, cleanliness becomes paramount. Consider whether you would opt to eat in a restaurant if it had the same cleanliness as a cow’s udder or a parlour. Yes, the milk is often (not always) pasteurised or processed, but blasting food in the microwave is not a suitable alternative to hygienic preparation.
While teat preparation can reduce the bacterial load on teats – and, therefore, the bacterial load in milk (Galton et al, 1984) – as well as the risk of environmental mastitis, it is no substitute for having clean cows to start with. Clean teats are associated with lower bacterial loads at the teat end, lower contamination with pathogens associated with environmental mastitis, lower subclinical infection rates (Schreiner and Ruegg, 2003) and lower bactoscans (Elmoslemany et al, 2009).
In the author’s opinion, routine udder cleanliness scoring is an essential tool in approaching milk hygiene control. It allows the role of the interaction of the udder and the environment to be semi-quantified and monitored over time. The author’s preference is for the udder cleanliness scoring system developed by the University of Madison-Wisconsin (Cook and Reinemann, 2007).
Failure in achieving adequate udder cleanliness needs investigating. The areas that contribute to udder cleanliness are listed in Panel 2.
It is standard practice that collecting yard, parlours, exit yards and passageways are cleaned twice a day. However, it is always worth checking this is the case. Anecdotally, a colleague was involved in mastitis consultancy overseas where the collecting yard was scraped twice weekly.
Again, with regards to parlour cleanliness, it is worth reiterating that the function of a parlour is to harvest food. Parlours should be clean enough after cleaning that you would feel safe eating your food there. During the milking process, the rapid removal of faecal contamination is key to this. However, the use of high-powered hoses in parlours should be avoided, as they create aerosols of pathogenic material. The preference would be to manually push the faeces towards the front of the cows using a small scraper and then use a low-powered hose to wash away the residue.
Parlour routine and machine maintenance represent a further opportunity for veterinary involvement in udder and milk hygiene. It is impossible to produce the ideal parlour routine for each scenario, as each parlour is different, each herd is different and each milker is different. Remembering the aim of the parlour routine is useful, though – to allow hygienic milk collection. This means reducing the bacterial load at the teat end, as well as encouraging milk let down to reduce bimodal milking and overmilking. Maintaining a rigid routine, with suitable timings, is key to achieving this.
Machine maintenance and performance represents an area of potential large losses to dairy farmers. A number of businesses – some vet-led, others not – specialise purely in this area. For both machine-related inputs and parlour routine, the author would recommend any vets wishing to further their knowledge and involvement in this area to undertake CPD, as some excellent options are available and attempting to cover this area and do it justice in a single article is not possible.
Vets have a great opportunity to help clients with management of both bactoscan and SCC before they apply penalties to the milk contract. The easiest area to begin any involvement is in udder cleanliness – assess the situation and then determine the area of the environment that needs work to improve hygiene. Further input in parlour function and routine are possible, but require further CPD as opposed to observations and a logical approach.
