A new breeding index for UK dairy herds operating block autumn-calving systems has been developed by the Agriculture and Horticulture Development Board (AHDB).

Similar to the existing Profitable Lifetime Index (£PLI), and the Spring Calving Index (£SCI), the new Autumn Calving Index (£ACI) represents the average additional profit a bull is expected to transmit to his daughters compared with a bull with an index of zero.

Each of three systems uses different weightings for various traits for calculating a bull’s index. Compared to £PLI, £ACI has more weighting towards fertility, percentage fat and protein, and lifespan. Compared to £SCI, £ACI will deliver more genetic gain with milk yield, lifespan and somatic cell count.

Marco Winters from AHDB said that £PLI is the recommended index for all-year round calving herds in the UK. “However, producers which have a split calving block in spring and autumn may be best advised to use the respective seasonal index when breeding each block,” he said.

Unlike £PLI, both £ACI and £SCI can be compared across different dairy breeds.

The new index will be launched on Tuesday 7 August, and rankings of bulls under each index will be available on the AHDB website.