A positive outlook for dairy cow fertility

Producers who ignore the genetics of fertility are missing the best opportunity they have for sustained and cost-effective improvements to the reproductive performance of their herds.

Dairy cow fertility is at the heart of herd profitability, driving milk yields, cutting interventions and improving cow lifespans.

Evidence supporting the role of genetics in improving fertility has accumulated every year, and we have new data to strengthen this link (see Figure 1 below).

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

Since the introduction of the female Fertility Index (FI) in 2005, the genetics of fertility have shown massive improvement across the national dairy herd.

This is also reflected in actual performance or phenotype (the solid line) and the genetic prediction of the Calving Index (dotted line), both shown in Figure 1.

However, today’s improvements follow years of decline when producers had little idea of any bull’s ability to transmit female fertility and were largely selecting for milk production.

This had the effect of not simply ignoring cow fertility but of 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.

Today’s sophisticated computing power and genetic indexing systems have turned this situation on its head. By developing more holistic indexes, such as the Profitable Lifetime Index (£PLI), which includes an element of fertility alongside other traits, it has been easy for producers to include fertility in their genetic selection criteria.

These indexes have also made it possible to ensure genetic choices made today do not have unintended consequences through correlations between desirable and undesirable traits, as was the case in the past.

Marco Winters, our head of animal breeding, says producers should be congratulated on achieving this turnaround of events:

“Their efforts have effectively cut average calving interval from a high of almost 425 days in the mid-2000s to nearer 395 days today.”

This progress was, in fact, predicted in an earlier genetic study around five years ago. At that time, AHDB forecast, from genetic trends, that the UK’s average calving interval would reach 390 days by 2024.

“With this projection still on target, it’s possible to confidently predict even more improvement ahead,” Mr Winters says. “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,” continues Mr Winters. “But impressively, this has been achieved at the same time as milk yields have significantly climbed.”

This achievement shows the power of genetics as a force for improvement, and it proves that it’s worth selecting even low heritability traits.

“Fertility has a heritability of about 3% [or 0.03], which is considered to be low,” explains Mr Winters. “However, heritability is the degree to which a trait is observed to be passed down the generations and female fertility is highly influenced by environmental factors – ranging from nutrition and housing to the timing of insemination and the fertility of semen.”

However, the genetic indexing system is effective in filtering out this external ‘noise’, and pinpointing cows with an innate fertility.

“If we can measure cows’ inherent ability to get in calf, it’s clear we can have a dramatic impact on animal performance,” he says.

Strongly urging every producer to consider the FI, Mr Winters adds it should be a key part of all dairy breeding strategies:

“We need cows to get in calf, and we need them to last, and the FI will help us achieve these goals. But fertility is also good for profit, welfare and the environment, and for this reason, it’s included in all our major indexes, including HealthyCow, EnviroCow and £PLI, as well as both of the seasonal Calving Indexes.

“Of course, improved management can have a more immediate effect on dairy cow fertility, but improvements made through breeding will be sustained over the long term and accumulate over generations.

‘’As with all traits, it’s important to consider both genetics and management, and to remember that having better genetics will make management easier.”

It’s important to know your own herd’s genetic merit for fertility, and you can check this by signing up for the AHDB Herd Genetic Report.

Most producers use this service through our website, where – as long as they are milk recorded – they can rank their own herd for many genetic traits, including the FI.

This allows them to track their progress over the generations and pick out animals with the best innate fertility and the ability to pass this on to the next generation.

We are holding workshops across the UK until 9 November, where you can learn more about unlocking your herd’s breeding potential.

At the workshops, we will help you to:

• Create clear breeding goals tailored to your own farm’s requirements
• Access and analyse your herd’s genetic potential with a personalised report
• Identify your herd’s baseline as well as areas for improvement
• Evaluate your own data and choose the right bulls for their herd

Essex farmer and NMR/RABDF Gold Cup winner John Torrance was quick on the uptake when the FI was introduced in 2005 and has been using it as a breeding tool ever since.

He says the index has transformed the performance of his 700 cows, whose fertility has steadily improved for around 15 years, alongside increasing production.

The Calving Index today is 40 days less than it was at the outset, dropping from 420 to 380 days.

At the same time, average production in his herd has increased to 13,500 kg at 4.0% fat and 3.28% protein and continues to rise.

He says:

“We’ve made giant strides since we began using the health indexes, and Oman bloodlines, in particular, have transformed health and fertility.”

With complete confidence in the data and, in particular, the choice of high daughter fertility bulls within the Holstein breed, he adds:

“The data doesn’t lie – before we had it, we were just choosing bulls on a whim.”

Also acknowledging the importance of activity monitors, he says they have played an important part, working in tandem with genetics.

Together, they have allowed the herd’s voluntary waiting period to be increased to 55 days, as Mr Torrance is more confident than ever of getting his cows in calf.

The pregnancy rate bears out the success of the policy and now runs at a massive rolling average of 29.5%.