At a Red Tractor herd health meeting for an autumn calving herd towards the end of the season in 2019 the control of somatic cell count (SCC) and clinical mastitis is reviewed, alongside herd antimicrobial use (AMU). The herd manager is concerned about an increase in the number of cows treated for clinical mastitis both prior to and during the winter housing period. The herd is 290 Holstein-Friesian cows averaging 9000 litres, calving between late July and early January, and milked twice daily through a 20/40 swing over herringbone parlour with a full pre-milking teat preparation routine, including fore-stripping. Both pre-milking teat disinfection (Hexaklene R, Agroserve; wiping with machine washable reusable towel cloths, Figure 1) and post-milking teat disinfection (Wynnsan All Seasons Chlorhexidine RTU teat dip, Wynnstay Agriculture; applied via a handheld pressure sprayer) are practised.
Lactating cow groups are housed in cubicles on mattresses bedded with a shredded paper product. Cows are dried off from May using a selective approach to antibiotic dry cow therapy based on an average SCC over the whole lactation of greater or less than 200 000 cells/ml. Cows above this threshold receive in-tramammary antibiotic (Ubro Red Dry Cow Intramammary Suspension, Boehringer Ingelheim Animal Health UK Ltd) and internal teat sealant (Orbeseal Dry Cow Intramammary Suspension, Zoetis UK Limited). Cows below this threshold receive internal teat sealant alone. The dry cows are kept in one 6-acre paddock for approximately 2 months to allow for buffer feeding prior to calving. Close to calving cows are then moved to a large loose yard that is bedded with straw three times a week and completely cleaned out every 6 weeks. After calving cows remain with the calf in the loose yard for 24 hours before being moved to the cubicle yard containing the high yielding cows.
All mastitis and treatment data are reported to an on-farm database (UNIFORM Agri) and individual cow SCC data are available via the Cattle Information Service (CIS). The herd SCC averages 170 000 cells/ml in the last 12 months, with the reported clinical mastitis rate too high at 42 cases per 100 cows/year. While herd antimicrobial use as measured by mg is low at 8 mg per population corrected unit, the defined daily doses average nearly four daily doses per cow in the last 12 months (https://dairy.ahdb.org.uk/technical-information/animal-health-welfare/amu-calculator/).
Cattle self assesment: QUESTIONS
- You wish to assess the predominant mastitis pattern on farm before you consider any management advice during this meeting. Outline the steps required to access the data from the CIS portal and use this information with the AHDB Dairy Mastitis Pattern Analysis Tool.
- Where does the Pattern Analysis Tool (shown in Figure 2 for this herd) suggest you should focus mastitis control advice during the management meeting? What two metrics using cell count and clinical mastitis data are likely to be important for this type of pattern?
- You review the two metrics discussed in question two in more detail using the TotalVet software (QMMS Ltd/SUM-IT). What are your thoughts on the data presented in Figures 3 and 4? What targets do you set for each metric?
- Given the current pattern analysis, what are your key recommendations likely to focus on in this herd given the calving pattern and management?
Self assesment: ANSWERS
- Free download software is available to convert Common Data Layer (CDL) file data and output a file to use with the AHDB Dairy Mastitis Pattern Analysis Tool (http://dairy.ahdb.org.uk/mastitis-pattern-tool). You download the CDL file for this herd from the CIS web page using your advisor login and password, and convert the data using the CDL Converter Tool (a YouTube teach video can be found at https://youtu.be/o3hm4sXR-ZXo). The Mastitis Pattern Analysis tool gives the output shown in Figure 2.
- The Mastitis Pattern Analysis Tool output in Figure 2 suggests that the ‘current’ (i.e. last 3 months) mastitis epidemiological pattern is one of predominantly dry period origin infection, and this has been important in the last 12 months as well (‘recent’). Using individual cow SCC data, metrics such as the dry period new infection rate will be an important metric for this pattern and is calculated by looking at the proportion of cows that are below 200 000 cells/ml at the last three recordings prior to drying-off that are above 200 000 cells/ml at the first milk recording post-calving. Using clinical mastitis records, an important metric is the dry period origin mastitis rate, calculated as the proportion of cows affected with clinical mastitis within the first 30 days after calving.
- The dry period new infection rate averaged 15% in the last 12 months. Figure 3 shows this metric for cows in second lactation and above (i.e. excluding first calving heifers). The dry period new infection rate was increased at the beginning and end of the 2018–19 calving season, with August and September at 20–30% new infections suggesting particular issues with dry cows managed at pasture. Figure 4 shows detail for the dry period origin mastitis rate, and while this rate is close to the target for the season, the farm is struggling to get below target during periods where greatest numbers of cows are calving, and this will drive the overall clinical mastitis rate in this herd. A useful target for the dry period new infection rate is <10% (cows and heifers); for the dry period origin clinical mastitis new case rate we quote less than 1 in 12 cows affected in the first 30 days post-calving.
- Control measures to discuss in this case will focus on reducing the rate of infection during the dry period, both for dry cows at pasture and dry cows housed. Areas of management discussed included the following:
- Selection of cows to receive antibiotic dry cow therapy — only those cows with one or more of the last THREE SCC prior to drying-off to receive antibiotic
- Infusion of all dry cow therapy — incorporate cotton wool and surgical spirit and follow the standard operating procedure at https://youtu.be/gJHv177D1xc
- Management of early dry cows at pasture — this was discussed in detail and plans altered to ensure three paddocks available and a rotation system such that early dry period cows spent no more than 2 weeks in any one area
- Management of late dry period cows — altered to house close to calving cows in a section of the empty lactating cow cubicles adjacent to the large calving yard
- Shed gates were opened to allow close to calving cows access to outside loafing space (Figure 5)
- Management of calving cows on the loose yard — altered to house calving cows only with a ‘just in time’ approach attempted. Space requirements at this level of production meant no more than 23 cows could be housed on this yard at a recommended stocking rate of 1.25 m2 per 1000 litres and cleaning out frequency was increased to monthly
- More ideas for veterinary advisors can be found using the AHDB Dairy resources available at https://ahdb.org.uk/knowledge-library/dry-cow-management-a-practical-guide-to-effective-mastitis-control.
Follow up in this herd focused on the dry period new infection rate after the August and September 2019 milk recordings. This was below target at the start of 2019, with only 4 out of 41 (9.8%) cows calving in with a SCC >200 000 cells/ml, compared with 9 out of 34 eligible cows (26.5%) in August and September 2018. For the September, October and November recordings, the dry period new infection rate averaged less than 5%.
In addition, new clinical mastitis cases in the first 30 days after calving have been significantly reduced, with the dry period origin mastitis rate averaging 0.23 in 12 (target less than 1 in 12).
Compliance in this herd was excellent, with nearly all interventions implemented, particularly those relating to the management of the dry cows at pasture and close to calving. This highlights the importance of specific measures relating to the predominant mastitis pattern on farm — and analysis of the mastitis pattern using cell count and clinical mastitis data.