Fertility improvement causes challenges with the control of mastitis infection

Friday, 24 January 2025

Ayrshire farmers Wallace and James Hendrie discovered an increase in mastitis infections causing high cell counts in their herd as a consequence of reducing their calving block. As mastitis infections cause financial losses, reduced milk yield and chronic high cell count, cows risk being culled. The Hendrie brothers needed to quickly address the issue before it also impacted the progress they’d made to improve fertility.

After starting their journey as one of our Strategic Dairy Farms, their goal was to improve fertility.

To achieve this, the brothers changed a number of management procedures designed to improve heat detection and conception rates. For heat detection, this included more staff time, automated cow behaviour monitoring, and screening cows for infection before the breeding season (metrichecking – a procedure to examine cows for endometritis).

To improve the conception rate, the brothers worked on dry-cow nutrition and milk fever prevention, as well as testing bulls and breeding plans and better record-keeping.

As a result, cows in the herd calving within the first six weeks increased from 71% to more than 80%. In the breeding season of 2024, the proportion of cows still not pregnant (empty) fell to 11.5% at Millands and 8% at the Netherlands (Wallace and James Hendrie’s farm adjacent to Millands), down from 23% and 15%, respectively.

However, this triggered an unforeseen increase in the rate of dry-period new mastitis infections, which averaged 25% of cows and heifers testing >200,000 cells/ml at the first milk recording after calving, well above their target of less than 10%.

Wallace Hendrie said:

“When we joined the strategic programme, we knew we wanted to look into tightening up our calving block and improving our herd fertility.

"During this time, we didn’t consider that this would increase the rate of mastitis infections in our herd.” 

The improvement in fertility increased the pressure on their calving pens and staff, increasing the rate of mastitis infections. Discovering this problem led to Wallace and James discussing it as part of the AHDB programme to help them better understand the cause of this increase.

After consulting with Doreen Anderson, AHDB's Senior Knowledge Exchange Manager for Scotland, they collaborated with vet James Breen from Map of Ag to better understand and lower their mastitis rate.

James visited the farm in March, observing the cows at calving, as well as looking at the milking cows to gather more information about current management.

The key areas observed on farm included dry-cow management in cubicles, calving yard management, how the team managed the milking routine, milking-cow living space, ventilation, outside space and feed space.

Finally, James used our Mastitis Pattern Analysis Tool (MPAT) to understand and analyse their milk-recording data. This highlighted that the pattern of infection was largely environmental, with a significant risk of infections occurring during the dry period when cows were housed in cubicles and on the loose yard calving pad.

Environmental mastitis infections during the dry period will cause increases in cell count as well as clinical mastitis cases within the first 30 days after calving.

While factors relating to milking-cow management, such as parlour routines and machine function, are always important, James emphasised that the primary focus for this herd should be on implementing changes to dry-cow management ready for the 2025 calving season, including administration of dry-cow therapy.

A selective antibiotic dry-cow therapy approach for cows with cell counts above 200,000 cells/ml was implemented to cure existing infections of high cell count cows.

The key area identified for improvement was the calving yard, and the team at Millands discussed ideas for doubling the size of the bedded area by moving their silage clamp and redesigning feed access.

The group also discussed allowing outside living space off the yard, aiming for at least 3 sq m of additional space per cow. These measures will reduce environmental mastitis infections through reducing pressure during calving.

“Reviewing what we are already doing and having an honest conversation with James has helped us to pinpoint our current approach to mastitis control and what may be causing a spike in cell count,” Wallace said.

James highlights the importance of regular milk recordings to monitor new infections and understand the likely source of infection in your herd.

At Millands, James points out that dry-period management in 2023 and 2024 appears to be the likely cause of the elevated cell counts. As a result, continued monitoring of the dry-period new infection rate will be essential to understand the impact of the changes made to dry- and calving-cow management during this winter.

James Breen’s top tips

Top tips for drying off cows to reduce risk of mastitis infection during the dry period:

  • Separate drying off from other tasks, such as foot trimming
  • Dry off in the parlour after milking
  • Use a pre-milking teat disinfectant with 30-second contact time, and wipe dry
  • Use cotton wool and surgical spirit to clean teats
  • Let cows stand for 30 minutes after administration of dry-cow therapy
  • Avoid running cows through footbath straight after drying off

Top tips for reducing environmental mastitis infections during the dry-cow period:

  • New, clean, dry bedding applied at least daily for dry-cow cubicles and yards
  • Scrape dry-cow and calving cow passageways and feed areas daily
  • Think about stocking rate to minimise infection pressure. For example, aim for 1.25 sq m of bedded area per cow for every 1,000 L herd average yield for dry cows managed on loose yards. For example, aim for 10 sq m bedded area per cow for an 8,000 L herd
  • Completely clean out dry-cow loose yards at least monthly
  • Look to provide living space away from the bedded areas, such as outside areas, to reduce contamination of the bedded area

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