THE question was posed by Jim Begg, of Dairy Co. UK, “Are vets happy with milk processors?” In his view one should never combine vets and happy in the same sentence.
Highlighting the reasons for controlling cell count from a purchaser’s perspective, the veterinary aspects of animal welfare are now an issue for customers and therefore an issue for processors. He stated that processors “take mastitis seriously” and he believes that investment in communication is as important as investment in research.
There is a need to improve economic data and knowledge and to raise awareness on farms and in factories, he said.
Well over a hundred delegates attended the 21st British Mastitis Conference in October and approximately a quarter were veterinary surgeons in practice. Technical specialists from animal health companies and organisations mingled with academics and researchers.
One of the mainstays of this gathering is the posters and this year there were 14 presentations for delegates to ponder and vote on. Some of the work highlighted advanced understanding of scientific issues related to the mammary gland and aspects of infection, others developed the use of data with a smattering of improved therapies, diagnosis and practical aids for mastitis control.
The winners of the shield were James Hanks and Andy Biggs for “The correlation between somatic cell counts around calving and cow longevity”. Details of the posters and papers are in the proceedings which can be found on www.britishmastitisconference.co.uk.
Nutritional strategy
The impact of nutrition on mastitis and somatic cell counts and the practical application in typical UK feeding and production situations was presented by Richard Vecqueray (Evidence Based Veterinary Consultancy Ltd).
Cows with dirty udders are more likely to have major pathogens isolated from milk samples and loose faeces contribute to the level of contamination. Dietary acid detergent fibre (ADF) is a marker for structural fibre and the more fed the stiffer the faeces. However, consistency is hard to predict accurately and there is a dearth of scientific information.
A nutritional strategy to create firmer faeces includes the diet content combined with improvements in cow comfort, lying times and cudding times to improve salivary buffering of the rumen.
Detailed considerations were also discussed of the value of controlling milk yield prior to drying-off, controlling milk fever and controlling the nutritional influences over a dairy cow’s immunity, which includes reducing the severity of negative energy balance and fatty liver, supplementing with micronutrients and altering dietary fatty acid type.
It is accepted that the associations between somatic cell count and nutrition are weak compared with those associated with hygiene and environmental challenge. It is important to integrate much of what is known into daily rations and advise on how cows are managed and fed. An overarching point is to “do everything possible to minimise weight loss”.
Cell counts
So you think you know about cell counts, that have been around for decades. Andy Biggs (Vale Veterinary Group) has been considering the fine detail of cell count interpretation and his paper needs to be considered in full.
Where individual cow cell counts are used to decide on the form of therapy at drying-off, the cut-off level is significant. At 200,000 cells per ml the sensitivity and specificity is around 75%. Therefore, 75% of cows with an infection have a cell count of more than 200,000 and 75% of uninfected cows have a cell count of less than 200,000.
If it is important to include only uninfected cows in a group, then the threshold can be lowered, which will exclude some cows that may be uninfected but that is better than including infected animals in a “clean” group. Interpreting the data more accurately is therefore a valuable tool for advances in mastitis control.
Interpretative software for the use of veterinary advisers is available online. Examples are www.nmr.co.uk and www.thecis.co.uk.
Action lists on somatic cell count are indicated by analysis of the data and demonstration farms are presented at the websites. With over half a million cow records available for analysis through National Milk Records, the interpretation of the longevity of infections is informative.
The influence of one high count quarter may mean that the overall cell count remains below 500,000 cells per ml but the cow may present a high risk to others. Simply controlling cell count in high cell count cows over 500,000 cells per ml will miss important sources of infection. The duration of the raised cell count, with a volume of data for analysis, indicates the importance of identifying persistent infections.
A rise in cell count before and/or after the dry period indicates a significantly increased probability of failure to re-calve. Thus, cell count monitoring and fertility management have a supporting role.
An important development is to demonstrate the usefulness of incorporating clinical mastitis records from the veterinary practice or farm computer into the cell count analysis. If clinical record data can be shown to be a more effective element in practical mastitis control, then more farmers will maintain accurate records.
Strep. uberis infection
The detailed responses to infection with Strep. uberis within the mammary gland are being investigated by a team of researchers from the Institute of Animal Health and the University of Nottingham. Tracey Coffey presented the background to the research and the influencing factors.
The host response to infection with a virulent field strain is compared to an avirulent strain. Once the initial host barrier system has been breached, the next level of defence is the innate immune system. Data are being collected about the transcriptional changes within the somatic cells in order to develop understanding about the pathogenesis of disease and further control measures.
Indications are that both strains cause a neutrophil response with a raised cell count but that the virulent strain of Strep. uberis is better able to colonise the mammary gland. Both strains are able to inhibit neutrophil function.
On slaughter, the invasive strain had induced gross pathological changes, which were absent from the noninvasive strain.
There are indications that the genetic make-up of the cow indicates a susceptibility to Strep. uberis infection. Knowing the disease profile during the course of infection will enable vaccination, therapy and management of the cow to be better targeted.
Automated milking
Mastitis detection is a developing area that is applied with automatic milking systems. John Baines (Fullwood Ltd) indicated that a combination of sensors is required, including observations of the cow, mechanical technology and clinical recording.
Sensor technology for mastitis requires an intelligent management system to permit management by exception. Olde Riekerink (The Cow Doctor Inc.) described a study where automatic teat dipping and backflushing of clusters yielded benefits from six months after installation. Improvements were seen in new intramammary infection rate indicated by a reduction in bulk and individual cow milk cell count.
Basic hygiene was highlighted by Alison Cox (Johnson Diversey) and a survey of farms has shown that, on farms struggling with mastitis, hygiene is given inadequate or varying degrees of priority. Lack of knowledge is identified with a perception that there is insufficient time or that improved application is too costly.
A cost calculator for mastitis is available at www.mastitiscontrolplan. co.uk and Martin Green (University of Nottingham) demonstrated the practical approach to assessing the cost benefits of mastitis control, which is available to all mastitis advisers. This forms part of the Dairy Co. Mastitis Control Plan.
Detailed information is available and the variation from farm to farm is considerable. Clinical mastitis costs, for example, in terms of pence per litre of production, range from below 1p to 10p. Making an assessment on the minimum return on investment is an overlooked but critical part of mastitis control.
New Zealand experience
Controlling mastitis in pasture-based systems in New Zealand was explained by Katrina Roberts (Animal Health Centre) and with yields of 3,500 litres per cow and an average herd size of 350 cows, with minimal labour, there is little comparison with the UK.
A control programme for environmental pathogens has been developed to take account of local conditions, with tight seasonal calving and the attitudes of owner operators, share milkers and contract milkers. There is considerable underestimation by farmers of the true costs of mastitis and interaction with “rural professionals” is a positive influence.
Farmer beliefs and motivation are seen to be as important as technical knowledge in disease management.
