Spring calving herds to have genetic index update

Producers running grazing-based, spring calving systems will soon benefit from a refreshed Spring Calving Index (£SCI). We have worked closely with producers to make sure the index better reflects their systems’ needs.

From April, the index will be weighted against tall, high production animals, some of which previously appeared high in the £SCI rankings.

Although the formula for £SCI will not change substantively – continuing to reward high-quality milk, fertility, health, functional type and efficiency – a penalty will now be introduced for high-production daughters that have a high energy demand.

Our head of animal genetics, Marco Winters, says the earlier approach worked well in systems where feed can be increased to match performance, but this doesn’t reflect the realities of spring block calving.

As he explains, some cows can produce impressive yields but only if they receive more concentrates:

“That’s not the philosophy of spring calving producers who are aiming to make milk from grazed grass and a very limited concentrate intake.”

Producers told us that high-energy demand cows often slip into a negative energy balance on grass-based diets.

To address this, the index sets a limit. Animals that have a total dry matter intake requirement of more than about five tonnes per lactation will now be penalised.

These changes are expected to reshape future bull rankings.

Some high-production Holsteins might move down, while more Friesian (including Irish and New Zealand) and Jersey genetics are likely to rise.

Producers have told us they would like to see the £SCI ranking feature more bulls which breed smaller daughters with lower maintenance costs and lower energy demands.

We’ve revised the index to do exactly that.

The group is confident that with the changes, producers will become more focused on genetic improvement as the uptake of £SCI grows.

“The revised £SCI ranking will help producers identify the best genetics to improve profitability in UK farming and economic conditions.

"It's far better to use a UK index than one which has been developed for milk payment structures or climatic conditions in another country, which we know has been a temptation of some spring, block calving produce.

“The changes we have made place less emphasis on big output and more emphasis on the right cow for the system, ensuring £SCI will be better suited for UK producers than ever before.”

Alongside the update to £SCI, more spring calving producers are seeing the benefits of using sexed semen.

In the past, many herds used dairy semen across most cows.

However, with the improvements to £SCI, combined with genomic testing of heifer calves, farmers can target sexed semen more effectively.

Genomic testing is also extending to crossbred animals, creating opportunities for all types of herds.

Better knowledge of female genetics and more accurate sire selection can help drive long-term progress in block calving systems.

• Moderate cow size
• Efficient grazing genetics
• Fertility
• Survival and low empty rates
• Milk solids from grass
• Components that suit solids-based milk pricing

• Bulls that breed large, high-maintenance cows
• Daughters that need excessive concentrate feeding to produce milk

For farm manager Keith Davis from Lydney Park Farm in Gloucestershire, the changes to £SCI are welcomed.

He not only welcomes the new developments in £SCI but has been part of the working group which has steered the changes.

Keith has always aimed for moderate-sized cows that fit his block calving system. He wants cows of around 500 kg producing 500 kg of milk solids from a grass-based diet.

He has used £SCI for many years to drive genetic progress.

The farm’s 850-head herd, which includes Jerseys, New Zealand Friesians, British Friesians and some Holsteins, has exceeded its initial target, producing around 509 kg of solids from a 510 kg cow.

But Keith has found that larger Holsteins struggle:

“When our cows get too big, that’s detrimental in this system, as they can’t eat enough feed for both their maintenance and milk production.

“If a Jersey needs about eight hours a day of grazing to maintain her bodyweight, a Holstein needs nearer 12 hours for hers. The bigger Holsteins just run out of time to graze enough grass.”

The system is designed to use around 500 kg of concentrates per cow per year, although poor grass growth can sometimes push this higher.

The herd’s average yield is around 5,200 kg at 5.3% fat and 4.1% protein, with around 3,460 kg coming from forage.

The milk is sold to Yeo Valley via First Milk through the Naturally Better Dairy Group, whose focus is on regenerative farming practices.

For Keith, the updated index is a welcome improvement:

“We will definitely be using £SCI for genetic selection as I feel it more closely reflects the type of cow we need for our system.”