The future is bright for dairy cow fertility

The genetics of dairy cow fertility have transformed since the early 2000s. AHDB’s Marco Winters predicts the national herd will return to 1990s fertility levels before the end of the decade.

About five years ago, Marco Winters, AHDB’s Head of Animal Genetics, predicted the average UK calving index across the national dairy herd would hit 390 days by the end of 2024. That was at a time when the calving index was over 400 days.

With 2023’s figure projected to be around 393 days, he can confidently say this prediction is on track.

Today, he’s projecting further ahead, and he says the country will reach an average calving index of 385 days before the end of the decade.

He bases his prediction on genetic trends for fertility, which have been transformed over the past 15 years.

Figure 1. Actual and estimated calving interval by year of calving

He praises Holstein breeders for this. They have embraced the female Fertility Index (FI) and used it in their genetic selections since 2005. He is also fulsome in his praise for the Holstein breed, which has responded so well to genetic selection.

But the picture wasn’t so rosy before FI launched. Today’s improvements follow years of decline when producers had little idea of any bull’s ability to transmit female fertility, and they were largely selecting for milk production.

This had the effect of not simply ignoring cow fertility but positively selecting against it.

This was driven by the moderate negative correlation between milk production and fertility which was known at the time but was difficult to address.

However, today’s sophisticated computing power and genetic indexing system have turned this situation on its head.

Marco said:

“It’s allowed for the development of more holistic indexes, such as Profitable Lifetime Index, which includes an element of fertility alongside other traits.

“By using £PLI and other modern selection indexes, it’s been easy for producers to include fertility in their genetic selection criteria, without compromising other traits.”

With his earlier prediction still on target, Marco predicts further improvement.

“This improvement will be slower, as we’ve taken the low-hanging fruit, but we expect to continue to cut calving interval by about one day every year over the next five years.”

This puts the national dairy herd on target for a calving interval of 385 days by 2029.

“This will bring us back to the fertility levels of the mid-1990s, but impressively, it has been achieved at the same time as milk yields have significantly climbed.”