Genomic testing is widening the gap between best and worst herds

Dairy producers have been able to genotype their heifer calves since 2012 and increasing numbers are doing so. A widening gap in genetic merit is opening up between the herds that test and those that don't.

The genomic testing of dairy heifers is having a profound effect on the genetic merit of the national dairy herd, with the gulf between the best and worst herds noticeably increasing.

This pattern has been revealed by the latest analysis from AHDB, which has identified a £193 difference in the average Profitable Lifetime Index (£PLI) between the most- and least-engaged herds.

Producers using genotyping services for 75–100% of their dairy heifers had an average PLI across their 2023 calf crop of £430. This compares with a £237 PLI for those herds which test 0–25% of their heifer calves.

Marco Winters, head of animal genetics for AHDB says this represents a massive difference in profit potential between the best and worst herds:

“Improving genetics is probably the cheapest and most sustainable way of making long-term improvements to any herd, and when you’re using a genetic index which has been developed specifically to increase profitability, this feeds straight through to a farm’s bottom line.”

The theoretical value of this difference is said to be around £19,300 for a typical, 175-head herd. However, analysis of actual margins from farm business accounts has revealed the advantage of a genetic difference of this magnitude to be over £50,000.

Alongside this improvement has been a sharp increase in the number of herds engaged in genomic testing their females.

This has now risen to 100,000 head per year, or roughly 20% of the dairy heifer calves born in the recorded herd. This is projected to increase by around 15% in 2024, and represents uptake across the Holstein, Friesian, Ayrshire, Jersey and Guernsey breeds.

“All of this tells us that genomic testing of females is no longer considered to be for the elite, as it may have been in the early days of the technology,” says Mr Winters.

Drilling down into why it is making so much difference, he says one of the first advantages may be unexpected.

“It’s surprising how many animals have been misidentified, often assigned the wrong sire, and sometimes even the wrong dam,” he says.

In fact, around 17% of calves have their sires updated when the genotypes are analysed. This is either because the wrong sire was recorded (7% of cases), or the sire was not recorded at all (10%).

Dam misidentification runs at a lower proportion but is still an issue.

“This means that if farmers think they are breeding from their best heifers, this may not be the case,” he says. “This has implications, not just for the quality of their replacements but also for inbreeding, through their choice of subsequent matings.”

Other specific benefits are highlighted when individual traits are tracked across the different groups, not least seen in female Fertility Index (FI).

The average FI for calves in the non-testing herds is 3 points, compared with 4.7 for the testing group.

This means those engaged in testing can expect to have shorter calving intervals and better non-return rates, as well as improvements in other, related, parameters of fertility.

“Genomic testing of females was actually introduced to UK producers in 2012, and it is interesting to plot progress in the run-up to this date,” he continues. “For FI in particular, this shows the worst herds today – which are not engaged in genomic testing – were actually the best, back in 2005.

“We can’t explain this pattern with complete confidence, but it makes sense that progressive producers who are genetically engaged have moved their breeding focus from almost exclusively milk production 20 years ago, towards the health, management and fertility traits today,” he says. “Conversely, those who aren’t so engaged in their herds’ genetics, may have had lower production – itself related to better fertility – 20 years ago.”

Similar benefits are seen in the top quartile when fat percentage is tracked, although all four groups have made steady genetic progress.

“It’s clear that virtually every producer is focused on this trait for obvious commercial reasons, but again, those with more information are doing the best job,” he says.

Maintenance Index shows a similar progression, with the herds most engaged in genomic testing breeding cows with the lowest maintenance costs.

“This is particularly encouraging as maintenance costs are closely related to cow size, and the attitude to this has been slower to shift,” he says. “This is not helped by the difficulties farmers have in finding smaller bulls, after many years in which their size has been on an upward trend.

“However, the last 10 years show some downward movement, particularly in the herds most engaged in testing. But we do need to note the kink at the end of the line and avoid any return to larger, heavier cows which are more expensive to keep,” he says.

On balance, Mr Winters says that the trends on display are very encouraging and farmers should be congratulated for the improvements they’ve made.

“It’s important to note that the genetic benefits seen in the top herds are not necessarily only a consequence of heifer genomic testing,” he says. “Genomic testing is just one tool with which these farmers are probably engaged, and they are likely to be generally more switched on to genetics, and potentially making better genetic selections.

“The key point to note is the scope for genetic improvement when more accurate information is used,” he says. “The financial case should be compelling to every producer – there is free money to be had, and all you have to do is choose better genetics!”

Farmers can benchmark their herd’s £PLI using our Herd Genetic Report which is available for all producers who are fully milk recording.