System now a factor in revamped genetic indices

Published 26 August 14

August 2014 sees the introduction of a revised Profitable Lifetime Index (£PLI) and a brand new Spring Calving Index (£SCI) from DairyCo’s Breeding+, designed to meet the needs of the UK’s increasingly specialist dairy farming systems.

Story 5 Graph1Graph 1 Relative genetic gain in key management traits between 1998 and 2013, based on insemination data recorded through milk recording (CIS, NMR, UDF)

The revised £PLI builds on the progress already made within UK genetics in recent years (see Graph 1) and increases the emphasis on traits highlighted as the most important to dairy farmers. 

Through national recording and genetic evaluations, it is now possible to select for over 30 different traits, enabling producers to breed the right cow for their system. Graph 2 shows the main changes of the revised £PLI, which promotes yield while maintaining milk quality and increasing focus on the main health traits – Fertility, Lifespan and Somatic Cell Count, along with the newly-introduced Calving Ease score.

Maintenance has also been introduced to identify more efficient animals. The changes will also ensure progress made in recent years on functional type traits of legs, feet and udders will continue.

Story 5 Graph2

Graph 2 Relative genetic weighting for a range of traits, based on the average of top ranking bulls for the previous and current £PLI

Herds with autumn-block or all-year-round calving should now use the revised £PLI and the advice remains the same: only use bulls with a £PLI above the best cow within your herd and place additional emphasis on the key traits that need improving within your herd.

Accessing your Herd Genetic Report (HGR) will outline the genetic potential of your
milking herd.


The new Spring Calving Index (£SCI) has been specifically designed for spring block-calving herds making extensive use of grass and targeting yields of around 4,500kg. Although it might look similar to the £PLI, the economic modelling used to develop the £SCI is based on far lower input costs over autumn and winter, an increased emphasis on milk quality over quantity and maintaining and improving management traits. Graph 3 shows the breakdown of the new £SCI.

Story 5 Graph3

The £SCI has been developed at the request of those running spring block-calving herds, to allow them to make a more accurate comparison of bulls to be used within the UK environment and management systems.

Unlike £PLI, this is an across-breed evaluation – so bulls of one breed can be compared directly with those of another, for example, a Jersey sire with a Friesian.

Graph 3 
Relative weighting of traits within £SCI.

A last word on genomics – the development and introduction of genomics over the past couple of years has given those breeding their own replacements a new way of selecting young sires with far greater accuracy than before.

Historically, young sires or test bulls were marketed with reliability figures of around 35%; the introduction of genomics has increased this reliability to 69%, giving farmers a far greater ability to confidently mate cows with young sires.

Genomic testing is also playing an important part in research and development. The technology is being applied to a number of research projects and may support the introduction of Feed Efficiency into the £PLI and £SCI in due course. For further details on the project please see the FE consortium presentation.

Research in the pipeline

As well as the revision of the indexes, further DairyCo-funded research and development work is being undertaken to ensure continued fine-tuning of genetic evaluations for the future.

The heritability of bTB resistance is currently being studied at SRUC and the Roslin Institute in Edinburgh by evaluating all bTB-positive cattle showing visible lesions. The project should conclude next year and a ‘bTB resistance’ index will be available at the end of the project. Further details can be on the DairyCo website under ‘Research and Development’, or by clicking TB resistance.

DairyCo, together with EBLEX and HCC, is also co-funding research into carcass values, involving the analysis of abattoir data to develop an index for carcass weight and quality. Beef from the dairy herd can generate a significant income on many dairy farms and this work will enable farmers to make strategic decisions when looking for additional income.

To aid this project, farmers are being asked to record sire details on all passport applications, including those for bull calves. More information can be found on the EBLEX website under  Carcass trait evaluation and Carcass trait evaluation - phase II.