Wednesday, 26 October 2022
As the size of dairy cows increases, their management becomes more difficult and feed efficiency declines. But a change of mindset is needed to halt the trend towards bigger cows.
When it comes to dairy cows, size matters. And contrary to popular belief, bigger isn’t better. In fact, according to Marco Winters, head of animal genetics for AHDB, the size of cows has been steadily rising since the mid-1980s, and there’s no sign of this trend abating. This is important because the average farmer in the UK is now feeding and managing a weight equivalent to 10 extra cows, for no other reason than cows are bigger than they were around 30 years ago.
Of course, this trend has occurred alongside vast increases in milk production. But with the precision of modern breeding tools, there’s no reason why improvements in production cannot be made without increasing the height and weight of cows. However, if dairy producers fail to reverse this upward trajectory, the average UK Holstein will become even more expensive to maintain over the years ahead.
But all signs are that breeders and AI companies have not responded fast enough to the warning, as whilst genetic trends for almost every other trait – from fertility and mastitis resistance to milk solids and somatic cell counts – are all heading in a favourable direction, the size of cows continues to relentlessly rise.
“Everywhere I go, farmers tell me they don’t want bigger cows, but all the genetic trends tell us that’s what they are breeding,” says Mr Winters.
This is in spite of the negative weighting for bodyweight that’s built into national breeding indexes such as £PLI (Profitable Lifetime Index).
Andy Rutter, who farms in partnership with his parents and sister at Clayhanger Hall Farm near Crewe in Cheshire, says he is baffled that farmers continue to select for bigger cows.
He says: “Every time we have an accident it seems to be with a big cow. She does the splits, gets stuck, has a displaced abomasum – especially if you pull out a big calf and are left with a big gap.
“It’s very noticeable that there are more issues in the taller, heavier cows,” he says.
For this reason, he’s been actively selecting against size since he took responsibility for the herd’s breeding policy in 2018, despite being warned by some against taking this direction.
“We were told that breeding against size would give us cows that were unable to compete in the herd. But we have actually found the complete opposite; smaller cows are definitely more confident on concrete and show bulling more strongly.”
This is especially noticeable in the Clayden 380-head milking herd which is managed as one group.
“Heifers have to sink or swim within that group, and five or six years ago, a lot were sinking,” he says.
Selecting bulls for negative stature
Reducing cow size has involved paying close attention to the breeding indexes at his disposal, with the most obvious trait avoided being positive stature.
“We would rarely use a bull with more than zero for stature,” he says.
However, he warns that with a rolling base – in other words, a new breed average calculated each year for genetic evaluations – it’s easy to lose track of how big a bull’s daughters will be.
“A rolling base is brilliant for providing accurate, up-to-date information, but it hides everything that’s happened before,” he says, alluding to one reason why producers may not realise they’re selecting for bigger cows. “If you add up all the base changes for stature it would be frightening. It means that a slightly negative stature bull today would have been positive last year and strongly positive six years ago.”
But in addition to stature, he also seeks bulls which score well for some of the industry’s more modern genetic traits which are related to size.
“I’ve been using Maintenance Index as well as stature, as we’re trying to breed a more efficient cow,” he says.
However, as Mr Winters remarks, the UK as a whole hasn’t followed suit.
“Maintenance Index has continued to get worse across the national herd, ever since it was introduced around eight years ago,” he says. This is shown in graph 1 and is largely a reflection of the increase in cow size.
“The graph shows that over the past 30 years, Maintenance Index has risen by at least 15 points, translating to over 30kg genetic difference in the average weight of a cow in 2021 compared with a cow in 1991,” he says. “This extra bodyweight means the average, 200-head, UK herd is feeding the equivalent of close to 10 extra cows every day.”
Back in the Clayden herd, even newer genetic indexes are starting to be used, not only to breed out size, but to breed in efficiencies.
“Maintenance has been my proxy trait for feed efficiency, but now we have Feed Advantage, which measures exactly this,” says Mr Rutter. He refers to an index which was launched in 2021 and identifies bulls with the greatest genetic tendency to transmit good feed conversion efficiency on to their daughters.
Representing kilos of dry matter saved due to better feed conversion efficiency and lower maintenance costs, Mr Winters says the difference between the best and worst animals can be as much as 400kg dry matter intake in just one lactation.
Added to this is EnviroCow, also launched last year, which Mr Rutter is using more this year than when it was first introduced.
“I really like the EnviroCow,” he says. “When I really looked into it, I realised I should have been using it more.”
Formulated to help breed cows with the best environmental credentials, it will particularly reward those which are predicted to create the least greenhouse gas emissions in their lifetimes for each kilogram of solids-corrected milk they produce.
“It’s that combination of feed efficiency and kilos of milk solids we like,” he says. “We always want to select for positive fat and protein percentage bulls as, although we are not paid for components on our current milk contract, we need to make sure the cows have it in them if we need to push more for milk solids.”
All of this is reflected in the Rutters’ own herd whose average annual production (milk sold) is 10,600kg at 4.2% fat and 3.2% protein (2x). This is combined with a pregnancy rate that’s far above national average at 33% and a calving interval of 372 days.
Today, Mr Rutter and his father, Dennis, are more pleased with the herd and the latest intake of heifers than ever before.
“I was very lucky that Dad handed over the genetics to me,” he says. “He said I was going to be milking them so I should make the breeding decisions.
“He did question some of the things I used but now he has seen the results, and we are both really proud of our milking heifers.”
All of them have been bred to reduce overall size and stature and to improve their health, fertility, ease of management, efficiency and ability to make a profit.
“If we still had the cow we milked in 2018, I think we’d have struggled to make a profit, especially at last year’s milk price,” he says. “But the cows we’re milking today are much more fit for purpose than those we milked in the past.”
From a practical angle, he adds: “We installed a new parlour five years ago and we want the cows to fit into it in 20 years’ time.” He knows they’re unlikely to do so if he disregards stature and efficiency traits in his breeding policy today.