Average herd size and yield have increased by 30% since 1996, while labour on farms has dropped by 30%. It’s no surprise regular heat detection has been one of the first casualties.

But as figures reveal modern high-yielding Holsteins show heat less strongly, it means they need watching more to reduce the cost of poor fertility performance.

NMR’s marketing manager, Mike Blanshard, reckons the average herd could earn an extra 3-4p/litre purely on improving technical performance.

But this requires an appropriate management system in place to make up for the decline in performance, he says.

“Data from our farmers shows that as 305-day yields go up, fertility and technical performance go down and milk sold per cow per year goes down because of the effects of a longer calving interval, mastitis and lameness.”

Perception that the high-yielding cow doesn’t get back in-calf early has led to a slip in calving interval across all herd sizes.

Mr Blanshard says producers’ belief that high yielders could go on a bit longer has increased the number of days to first service.

Large herds need to use heat detection aids as herd owners become man managers and employ staff to do the cow managing, he adds.

However, heat detection in year-round calving herds, where fewer cows are on heat at any one time, shouldn’t be more difficult.

“In a 400-500-cow herd, there should be 30-40 cows every month on heat.”

But the biggest reason for variation between farms in heat detection is stockmanship, not genetics, says vet nutrition consultant Richard Vecqueray.

While he agrees high-yielding cows show oestrus less strongly, he finds good stockmen can overcome this.

“I visit smaller herds producing 12,000kg a cow with conception rates approaching 60% and good calving to first service intervals.”

The cow

Having the right kind of cow to suit the management system has become a bit of a clich.

But when it comes to getting large numbers of cows back in calf, the modern high-yielding Holstein isn’t helping.

US data from 5000 cows watched over a 24-hour period, shows the average duration of standing heat is just seven hours for a modern Holstein, according to Virginia Tech.

A cow is mounted on average nine times in this period, but almost 50% of cows have fewer than five mounts.

Additional data from Wisconsin University reveals Holstein cows show standing heat for 7.3 hours compared with maiden heifers at 11.3 hours.

Such figures simply reflect the effects of management and stress during lactation.

According to Mr Vecqueray, Holstein heifers are as fertile as Friesian heifers, but problems arise once they have calved and start producing high yields.

Environment

Confident cows are more likely to show signs of standing heat because they can be sure of good footing.

Yet many dairy units still have large areas of slippery concrete, which leads to cows being unwilling to stand for mounting activity, says Ayrshire-based fertility specialist Peter Ball.

Grooving floors and loafing areas is important.

“Cows tend to gather when on heat and loafing areas allow them to mess around.

Statistics show this leads to much improved oestrus detection,” he says.

As well as grooving floors, producers could install rubber flooring in key areas of cow traffic, says Mr Vecqueray, because it gives cows some grip and is better for their feet, which means they will stand.

Heat stress in large herds housing all year round is also becoming a big issue.

“Hot cows pant and they don’t swallow saliva, so they are susceptible to acidosis due to lack of buffering in the rumen,” says Mr Vecqueray.

“Dry matter intakes can also drop 10%, which then affects energy balance.

And the first thing to go is fertility.”

People

There is no substitute for observation when it comes to identifying cows on heat.

But today’s stockman on a large herd tends to be a man manager rather than a cow manager, says Mr Vecqueray.

The skilled stockman is spending too much time on physical jobs such as milking or scraping out, or the herd manager is tied to the office.

“This means computerised record keeping and aids to oestrus detection are vital.”

However, good stockmanship is also needed to get the complete picture, he adds.

“It’s important to know the stage after calving, what’s been served and what’s due for PD.

You need to get a good handle on things, measuring and quantifying problems to make the first steps of improvement.”

Mr Vecqueray suggests producers enlist the help of their vet and have one or two months off the daily grind of heat detecting and serving cows because it makes a big difference psychologically.

Cows should be observed a minimum 30 minutes twice a day and he says training other staff to spot bulling cows can increase the number picked up from 50% to 60%.

Having worked with large herds around the world, Mr Ball agrees that observation is still the key, but heat detection aids are invaluable.

Technology such as pedometers has come a long way and closed-circuit TV is now being developed for heat detection.

fwlivestock@rbi.co.uk