By Debbie James

Genomic testing replacement heifers has a cost benefit of £19.39 a heifer according to a three-year study involving nine Welsh dairy farms.

The project compared the difference between estimated breeding values based on parent averages – a composite of a heifer’s family pedigree – and genomic predicted transmitting ability (PTA) which provides information early on in a heifer’s life to allow breeding decisions to be made before rearing costs are incurred.

Genomic testing is now 60-70 per cent reliable for predicting future performance compared to just 35 per cent for parent averages but it adds an extra £25-£30 to rearing costs.

The European Innovation Partnership (EIP) study, which involved 432 Holstein Friesian heifers, weighed up this cost against the benefits and calculated a £19.39/heifer cost benefit – the total economic benefit was £46.89/heifer and the testing cost £27.50/heifer.

However, Victoria Hicks, of Kite Consulting, who analysed the results, says the cost-benefit figure does not include any additive and compound interest that investing in herd genetics creates.

“Any improvements in this crop of herd replacements will pass onto future generations,’’ she says.

Of the 432 animals tested, the project achieved a final dataset of 291 with genomic and traditional PTA results and complete 305-day lactation information.

Some animals didn’t fully reach the 305 days, had missing fertility information or their traditional PTA could not be recalculated because their sire didn’t have an official UK proof available.

A reduction of £44 in average £PLI (profitable lifetime index) from traditional to genomic proofs was significant, says Ms Hicks.

“The change in animal ranking is also important as your best or worst heifers might not actually be your best or worst heifers once you have sight of their genomic information.”

The most striking result was in the somatic cell count measure – the bottom 25 per cent of heifers ranked by genomic SCC index had the highest average number of high SCC occurrences and the highest cumulative SCC.

In contrast, for animals ranked by their traditional SCC index, the poorest SCC performance occurred in the top 25 per cent for both high SCC occurrences and cumulative SCC.

Fertility performance showed a difference of 18 days to conception between the top and bottom 25 per cent based on genomic fertility index but just four days when the traditional fertility index was applied.

This average difference worked out at 5.25 days – at £5/day for the extended lactation this added up to £26.25.

The benefit of genomic testing lies in the increased progression of genetic gain.

In the study, a theoretical selection point of £150 PLI was used to decide whether heifers would be bred to a beef or dairy sire. It showed the potential for breeding mistakes to occur when only traditional PTA values are used since 22.9 per cent of heifers were misidentified as being either above or below £150 PLI.

This resulted in lost £PLI potential of £6,914 for the next generation.

Argoed Hall Farm, Mold, was one of the farms involved in the study.

The farm supplies milk to Arla on a constituents-based contract – the herd is averaging 4.4 per cent butterfat and 3.5 per cent protein.

Its culling decisions had been based on fertility, lameness and mastitis but the business now intends to use genomics to factor production into the decision-making on which animals to keep in the herd and which to let go.

Genomic tests on the 400-cow all-year-round calving herd showed a big variation between animals, says Tom Bletcher, who farms with his father, Roger.

This data will inform their decision making going forward.

Tom admits he was initially sceptical about genomics but the results of the study had given him the confidence to use genomics going forward.

“As there is more and more focus around sustainability and lowering our carbon footprints we are going to need to be as efficient as possible and to look at ways to drive those efficiencies.’’

He plans to continue with his own testing now that the study has ended.