Genomic testing proves its worth

A recent study reveals a strong link between increased levels of genomic testing and faster genetic gains in dairy herds.

The youngest generation of dairy producers may only know an industry in which semen sexing and genomic testing are commonplace and are drawing on these tools on a routine basis to improve the profitability of their herds.

AHDB play the key role in providing producers with genetic tools and monitoring industry progress. We commissioned a recent study to look at UK herds’ genetic performance, breaking this down according to their level of female genomic testing: Over 75%, 50-75%, 25-50%, less than 25%

The study revealed a clear distinction across the four quartiles, with those most heavily testing (>75% of their females) developing the highest genetic merit herds. This is illustrated in graph 1, which shows those most engaged in testing had an average Profitable Lifetime Index (£PLI) for their 2021 calf crop of £500.

In contrast, the herds in the bottom quartile, testing 0-25% of females, had an average £PLI of around £321 in 2021-born calves.

This distinction clearly indicates that the herds testing the most set themselves up for an extra profit of £179 per animal, compared with those which have not engaged with female genomic testing.

This is because the £PLI on which they were measured for this study, theoretically translates to an extra £1 profit per point. In practice, actual animal performance underestimates the true value of £PLI, which in real costings by a recent independent analysis was shown to be worth £1.58 per point per lactation.

Marco Winters, AHDB head of animal genetics, says: “The link between genomic testing and genetic progress is encouraging, and indicates breeders are making good genetic choices with the data we make available.”

However, he is keen to point out the link between genomic testing and the herd’s genetic merit does not necessarily represent cause and effect.

He says: “These figures indicate that the more involved producers become in genomically testing their females, the better their herds’ genetic performance. This is almost certainly because they have identified and bred from their better animals, but there could be additional factors at play, such as their choice of better sires.”

A degree of divergence is indicated by the graph before female genomic testing was even offered (pre-2013), hinting that those heavily testing now were also making better breeding choices in the past. 

However, the extra accuracy of genomic testing appears to have widened the gap between the best and worst, as indicated by the diverging lines on the graph.

“Genomic testing in itself will not improve your herd’s performance and must go hand in hand with good breeding choices,” adds Mr Winters. “However, it does identify the best females born, which can be reared as replacement heifers. If semen is then selected with equal care, it is possible to make significant genetic progress, even in one generation.”

Used in tandem with sexed semen, the benefits will magnify further, concentrating breeding replacement heifers on the very elite within a herd.