The trend towards block calving systems continues for GB dairy

According to analysis by AHDB utilising BCMS data, the share of GB farms in 2024 running any type of block calving system has risen to 19.6%, while the number of farms running an all year round (AYR)* system remained fairly steady at around 35%. If we look over a longer time period, there has been a significant trend towards farmers adopting a specific calving system. In 2021, 48.4% of farms were categorised as non-defined* in their calving pattern; in 2024 this had fallen to 45.8%.

Source: BCMS, AHDB

Block calving systems have seen the largest uptake, having risen by 3.1 percentage points since 2021. Within this, Autumn* block calving has been the most favourable moving up 1.8 percentage points from 2021 to 7.2% of total farm numbers in 2024. This movement has exaggerated the peaks and troughs in the seasonal birthing profile of the GB dairy herd.

Source: BCMS

Larger dairy farms, in terms of number of births per year, tend to operate on a more defined system. In 2024, just 8.7% of the largest farms (calving over 500 a year) ran a ‘non-defined, calving system’, favouring an AYR calving pattern (64.1%). In comparison, 61% of the smallest farms (calving less than 200 a year) had a ‘non-defined’ calving system.

Farms with between 200–500 births per year, see a more mixed approach to operating systems with 47.1% AYR and 28.5% block. However, they do see a larger number in the non-defined group (24.5%).

The number of larger farms (those with over 500 births per year) has been increasing over recent years. Meanwhile, the smallest farms (those with less than 200 births per year) continue to decline, supporting the shift to AYR and block systems.

Source: BCMS, AHDB

*Definitions for analysis

2020 was the first time we were able to see the breakdown based on calf registrations for each farm in the country. Historically, the breakdown of system in GB has been based on farmers’ self-assessment of which system they believe they operate.

The data excludes any farms where all registrations were for non-dairy calves, and also excludes farms who had less than 25 calf registrations in the year. Our farm key performance indicators suggest block calving herds should target 85% of calvings within a 6-week window, although the 'good' level is set at between 70–85%. For this analysis we have used a wider definition of 4 months and 80% of registrations as set out below:

• Spring block: 80% of registrations occur within 4 months from 1 Feb to 31 May
• Autumn block: 80% of registrations occur within 4 months from 1 Aug to 30 Nov or 1 Sep to 31 Dec
• Other block: 80% of registrations occur within 4 months other than defined in spring or autumn block
• Dual block: 90% of registrations occur within the spring block or autumn block windows defined above.
• AYR: Registrations are spread relatively evenly throughout the year, but that can be based on a 12-month, 11-month or 10-month calving system. 12-month means each month sees 3.3–13.3% of annual registrations. 11-month means 4.1–14.1% of annual registrations in 11 months of the year, and 10-month means 5–15% of annual registrations in 10 months of the year.
• Non-defined: covers any farm not falling into one of the other categories.

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