In contrast to the mainly Spring Calving dairy herds in Ireland, typically dairy farmers in the United Kingdom operate an all year-round calving system (AYR), with 80% of farms falling into this category.

With an AYR system there is no seasonal emphasis on calving, and there are no periods when the entire herd is dry. These herds vary from extensive grass-based production to more intensive, high yielding indoor based systems.

The alternative to and AYR system is block-calving, here we will look at what block-calving involves and why come UK farmers are looking to make the switch.

What is Block Calving?

Block calving is when your herd has a specific period or “block” of time in which calving takes place. This can be one block where all cows calve in a defined 12-week period (or less), or Split-block, where cows calve in two distinct 12-week periods each year, usually Spring and Autumn.

What are the Benefits of Block Calving?

Labour efficiency

It can be easier to plan and manage labour resources on a block calving herd, due to having a set period of calving, breeding, and a dry period.

Cost Savings

Production costs can be reduced when all cows are on the same nutritional plan. A Spring Calving herd for example can have a greatly reduced cost of production from producing a larger percentage of milk from grazed grass.

Time Off

A predictable calendar and set calving period means you can plan time off for staff and yourself.



With all cows calving during a 12-week period, infrastructure can come under pressure. Calving pens and calf houses will need to be able to accommodate this larger volume, disease pressure can also be higher due to the numbers involved.

Labour During Calving

The calving period will be very busy! Extra hired labour may have to be considered for night-calving or calf rearing during the busy period.


Transitioning from AYR to block calving will mean a proportion of your herd will have to be left open for a period to move in line with the Autumn or Spring group. This non-productive period will affect cashflow during the changeover and needs serious consideration.

Herd Type

The fertility KPIs of a block-calving herd differ to that on an AYR herd. There is a much greater emphasis on fertility when trying to have cows calved during a set 12-week period. More extreme Holstein type cows may be less suited to this system.

For further advice on any of the above, please contact a member of the Moocall team to speak to some of our breeding specialists on +353 1 96 96 038 or email