Genomically testing replacements has flagged up a genomic profitable lifetime index gap of up to £286 between heifers at a Pembrokeshire dairy farm.

The Hannah family screened 94 heifers at 20 months old as a Farming Connect demonstration farm project.

Their aim is to fast-track genetic gain in their spring-calving herd and improve the lifetime productivity of cows by utilising information about an animal’s genetic merit before first service.

Based on the profitable lifetime index valuation, the top ranked animal had a plus-£282 genomic £PLI compared to the bottom at minus-£4, resulting in a lifetime earning potential gap of £286 between the two.

There was also a big range on milk solids scores between heifers at either end, from a high of 61kg to a low of minus 757kg.

As the farm supplies Arla on a solids-based contract, identifying animals which have the best fat and protein traits can make a big difference to the bottom line, says dairy business consultant Andy Dodd, of The Farm Consultancy Group, who analysed the figures for Farming Connect.

Even when set against a testing cost £25-£30 a head, there can be a big cost benefit from genomic testing, he believes.

At Mountjoy, the genomic somatic cell count (SCC) index ranged from +16 in the bottom ranked heifer and -4 in the top.

“Genetically, this is one trait that flags up as one to improve,’’ says Mr Dodd.

“SCC is challenging to select for in spring calving herds using New Zealand genetics as they only have a minimal weighting for SCC due to different milk contracts.’’

Although all the key transmitting traits tested for showed differences between the top and bottom, as a group overall the figures were quite similar.

Mr Dodd attributes this to a tight breeding policy over the last 10 years.

But further gains can be made from inseminating with sexed semen based on a heifer’s genetic merit ranking, he adds.

To test how well the genomic data reflected the actual performance, in-calf heifers were also tested to allow the results to be compared against their QMMS milk recording data from 2021.

Mr Dodd says the trend on fat and protein showed a “reasonable’’ correlation between genomic prediction and first lactation data.

“This is positive and what we would expect,’’ he says.

There was much less correlation on SCC as a group average.

“But when we look at individual animal recordings and genomic predictions, the link is clear to see with animals predicted to have poor SCCs often showing a spike at some point during lactation,’’ says Mr Dodd.

In the long term, the use of genomic testing on females would offer similar benefits to testing bulls, enabling highly accurate selection of replacements, he suggests.

“Selecting for only the best replacement heifers and those that best suit the farming system can have a positive effect on farm profitability.’’

But sire genomics are important too.

“You have got to select bulls that are going to do the other half of the job, in this instance selecting bulls that are above 286 on £PLI, so using PLI as a filter then selecting the desired traits,’’ says Mr Dodd.

The Hannahs had planned to use the results from the genetic testing to inform their decision making around which heifers to retain but, after a bovine TB breakdown resulted in a loss of 40 animals from the milking herd, all 2020-born heifers will enter the herd.

William Hannah, who farms with his wife, Heather, and his parents, Tom and Mary, says the project had been useful.

The results had shown the opportunity for herds to get a good idea of the potential for their heifers’ production from a genetic test alone.

But, he adds: “If you are looking to get data on your herd, you won’t beat milk recording for actual herd performance and, in particular SCC.’’