View PLI as ‘long-term’ dairy breeding tool

A growing number of UK dairy farmers are basing their long-term breeding strategies on lifetime production potential.

DairyCo extension officer Andy Dodd says farmers are recognising the value of profitable lifetime index (PLI) as a tool to shape the future direction of their herds because the benefits accumulate over generations.

“A herd can be bred to fit a system, whether that be a grass-based farm on a constituents milk contract or one with a high-input liquid milk system,” Mr Dodd told farmers during a DairyCo open day at Brynhyfryd dairy Farm, near Crymych, Pembrokeshire.

“More farmers are gaining a clear understanding of breeding and sire selection, using these to establish clear breeding plans. The long-term profitability of a herd can be improved through breeding.”

Mr Dodd warned that PLI should not be regarded as a means of achieving short-term gain. “Farmers need to consider what kind of farming operation they want to be running in 10 or 15 years’ time, not make a snap decision when they buy semen. It will be five years before the benefits of a specific bull come through, but for the herd as a whole the payback might not be for 10 or 15 years. It is very much a long-term process.”

PLI is the financial improvement an animal is predicted to transmit to its daughters in a lifetime. Every PLI point increase represents a financial benefit of £4.21 a head.

According to DairyCo, the top PLI herds are gaining an extramargin of £24,839 for every 100 cows compared with the average herd.

PLI includes non-productive traits such as fertility, lifespan and somatic cell count. Genetic trends in some dairy herds have been towards increasing milk production, but this has created a decline in genetic merit for butterfat and protein percentages, fertility and lifespan.

Infertility is a principle reason for culling dairy cows, emphasising a need to take account of sire fertility index.

“For many herds, the area that will need particular improvement is fertility and there are now more bulls available that will pass on good fertility to their daughters,” said Mr Dodd.

He advised farmers to stand back and assess the strengths and weaknesses of their herds. “Farmers need to be realistic about where they want to get to. If the herd has been bred heavily for one trait they might have to take a hit on another,” said Mr Dodd. “It may take several generations to get into the top percentile as farmers need to be realistic about what they can achieve rather than having to trade off other traits.

“We have got more information available now than we have ever had, so it is easier to make decisions.”

At Brynhyfryd Farm, Simon (pictured above) and Sian Davies select bulls on PLI and milk production is a key factor – the 235-cow pedigree Holstein herd produces 2.5m litres of milk annually. But other traits, such as somatic cell count, are important too. Mr Davies said using PLI does speed up genetic breeding, but he has taken on board the message that the process must be a long-term one. “It is something that can’t be rushed,” he admitted.

With a calving index of 418 days, fertility is an area targeted for improvement, but gains are also being made through good herd management. Mr Dodd highlighted one cow that scored -10 for fertility, but which had calved at 365 days one year and 363 days the following year.

“There has been a gain of two days, even though genetics show her to be -10 and this has been achieved through good management,” he said.

AI companies have played an important role in the process through increased listing of positive fertility bulls in their catalogues, he added.

However, fertility isn’t the only non-productive trait considered within the PLI index. Bulls carry proofs for lifespan and somatic cell count, and these should also be considered when selecting bulls.

“Sires should be screened on PLI in the first instance, but then a farmer must consider which fitness traits are important in their herd and ensure they are using bulls that fit their system.”

Inbreeding value should be considered carefully, too. “We would recommend that cows don’t go above 6.25%, but there are many herds that have cows above that level and some are significantly higher,” said Mr Dodd.

“Up to 6.25% there is unlikely to be any detrimental effect on herds, but above that fertility and milk production begin to be affected.”

He urged farmers to access their herd genetic report through DairyCo to gain an understanding of their herd’s genetic potential for all the traits, together with inbreeding levels of individual cows.

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