As dairy expansion slows, farmers will be finding it increasingly more difficult to achieve a high six-week calving rate. The target is for 90% to calve in the first six weeks of calving.

The figure can sometimes be clouded by the number of heifers that are entering the herd. So expanding herds can have a high six-week calving rate, even though actual herd fertility may not be all that good.

Looking at the six-week in-calf rate is a better measure of herd fertility. The target here is to have 75% of the milking herd in-calf in the first six weeks of breeding.

When heifers are included, the six-week calving rate should be in excess of 90% next spring.

The best way to measure the figure on the farm is to count the number of cows (second lactation and greater) that calved in the first six weeks after the due date last spring and compare this to the total number of cows that were bred the previous year.

In many cases, particularly where extra heifers are brought in, the six-week calving rate may cloud an underlying fertility problem.

Fertility remains a challenge for the Irish dairy herd and while improvements in genetics have been made, the national average six-week calving rate and calving interval are embarrassingly low at 65% and 387 days, respectively (the six-week in-calf rate is not known).


Before talking about on-farm practices for improving fertility, the first port of call should be to the herd EBI report. The herd EBI for fertility will have a big bearing on actual fertility performance.

Holstein Friesian herds should have a fertility sub-index of at least €110, while the Jersey crossbred herd should have a fertility sub-index of at least €65.

Improving genetics is a long-term play

The national average fertility sub-index across all herds is €48, which is way off the target.

This shows that many herds don’t have the genetic potential for good fertility and it also shows where the main focus should be when selecting bulls.

Improving genetics is a long-term play. After that, it’s down to management. Maximising the submission rate is the first task.

Farmers who have carried out pre-breeding heat detection should know which cows are not cycling by now.

These cows should be scanned to identify the issues. In some cases, they will not be calved long enough to have cycled, in other cases they will have cycled and just have had a missed heat, while in other cases they will be non-cyclers.

It is these cows that farmers need to act on as they can make up to 5% or 10% of a herd. Failure to get these cows served inside the first three weeks will make it very difficult to achieve the six-week in-calf rate targets.

The best policy is to get them scanned and treated by a vet as soon as possible. Some will require washouts and hormone treatment to treat cysts and other issues – the vet can prescribe different treatment options.

The majority of the cows at that scan should be perfect, but the objective is to pick up the problem cows

For farmers who have not completed pre-breeding scans, it is probably worthwhile getting the whole herd scanned as soon as possible.

If, as is likely, breeding has already begun, then the cows not yet served can be scanned.

Obviously, this is a more expensive option than pre-breeding heat detection but one that may be necessary, particularly where fertility performance is not that good.

The majority of the cows at that scan should be perfect, but the objective is to pick up the problem cows. Waiting until the end of the first three-week period is leaving it late.

If they are scanned on, say, day 24 and even if they get a CIDR/PRID fixed-time AI programme on that day, it will be day 34 before they will be served.

At least if they are served inside the first three weeks, even if they repeat they have a much better chance of going in-calf inside the first six weeks.

It might also be useful to scan cows at the end of the period of artificial insemination.

This will probably not affect the six-week in-calf rate, but it may affect the overall empty rate as it will help to detect false or phantom pregnancies and gives time to get these animals served.

Heat detection

Accurate heat detection and accurate use of heat detection aids is critical.

If you are doing something your way and getting good results, then keep at it.

Cows with tail paint applied for heat detection. \ Donal O'Leary

But if you are not getting the best results, something needs to change. Too many farmers are applying tail paint incorrectly.

The proper way is to apply a two-inch by nine-inch strip from the top of the tail head back. This is not a five-inch strip, or not halfway down the tail.

Applying tail paint correctly will help to identify more cows in heat.

Some cows will only be mounted two or three times. This means that only a very small amount of paint will be removed by these mounts, even though the cow is in standing heat.

If too much paint is applied then a smaller proportion will be removed by the mounts and, as a result, it will be much harder to identify that the cow is bulling.

Topping up the paint regularly will ensure there is good coverage and a good shine off the pain

Only applying the paint over the correct part of the body will mean that more of that paint is removed after even a small number of mounts.

Topping up the paint regularly will ensure there is good coverage and a good shine off the paint. Dull paint can indicate that the cow was mounted and should alert the farmer that the cow could be on heat or coming into heat.

Teagasc research has shown that if 25% of the paint is removed, there’s a 76% chance that the cow is bulling.

That, to me, is an amazing statistic and highlights the importance of good tail painting.

Other heat detection systems also have a role to play such as scratchcards, but farmers need to be prepared to replace these regularly to avoid false positives.

Maximising genetic gain

In herds that aren’t expanding, at least 25% of cows that are submitted for AI in the first three weeks should be given a beef AI straw.

These beef AI straws should be targeted at the poorest 25% of cows in the herd which ensures that you are not breeding dairy replacements from them. If sexed semen is being used, more beef AI can be used.

How? In a 100-cow herd, if 90% of the herd is submitted in the first three weeks and if 25% of these get a beef straw that means 68 cows get a dairy straw.

If 60% of these hold and if 50% are heifers, then you should have 20 heifer calves on the ground next spring.

Most importantly, these 20 heifers should be from the top 68 cows in the herd, in addition to the heifers bred from heifers.

The highest-EBI cows should get the dairy straw.

In short

  • The target six-week in-calf rate is 75% whereas the average six-week calving rate (including heifers) is 65%.
  • Identify non-cycling cows now and get them checked by a vet.
  • Correct use of tail paint will help to increase the submission rate.
  • Use beef AI on low-EBI cows in the first three weeks of breeding.