A six-week in-calf rate is important for driving dairy farm profitability, according to LIC’s Joyce Voogt.

Voogt, Manager of the LIC Reproduction Solutions Team in Hamilton, gave a talk on the importance of this Key Performance Indicator (KPI) to over 40 farmers in Dungarvan recently.

The New Zealand-based fertility expert explained that every 4% increase in six-week in-calf rate will result in a 1% fall in empty rate, in turn boosting milk solids production and farm profitability.

Along with boosting farm profitability, Voogt said that a high six-week in-calf rate can increase genetic improvement and herd quality as farmers have much more choice when it comes to the cows they can keep.

Why the six-week in-calf rate is important:

  • More days in milk in early lactation.
  • More AI bred replacements to sell or keep on farm.
  • Fewer empties and less wastage.
  • More choices to build the herd you want.

8 steps to maximising the six-week in-calf rate

1. Six-week in-calf rate targets

According to Voogt, a six-week in-calf rate is the number one of measure of a dairy herd’s reproductive performance and farmers should aim to have 78% of their cows in-calf after the first six-weeks of breeding.

Hitting this KPI will have a positive impact on the profitability of their businesses, but to achieve this target, farmers must focus on submission, empty and conception rate targets.

Key targets:

  • Six-week in-calf rate: 78%.
  • Empty rate: 6%.
  • Three-week submission rate: 90%.
  • Conception rate: 60%.


2. Managing your heifers

Heifer management also plays an important role in hitting this six week target, Voogt said, as 20% of the herd can consist of these animals.

Heifers should be treated like the apprentices in the herd, she said, as they have yet to reach peak production and it is important for these animals to return to the parlour for subsequent lactations.

When heifers and cows are mated at the same time, farmers should aim to calve down 75% of their heifers in the first three weeks of the calving season, she said.

This target increases to 83% when heifers are mated a week-to-10 days before the main breeding season on farm.


Mating heifers ahead of cows is a recommended best practice, but you have to feed budget for these animals as heifers can account for almost 20% of your herd.

Breeding heifers a week-to-ten days before the main herd gives them the extra recovery time they need to start cycling, she said.

Heifer breeding targets:

  • 75% of heifers should calve in the first three weeks of calving (mated same time as cows)
  • 83% of heifers should calve in the first three weeks of calving (mated before cows)
  • Heifers should be 60% of their mature weight at 15 months of age

The reproduction expert added that puberty in cattle is driven by weight and to get the best results at breeding, whether it be through bulls or AI, farmers should aim to have their heifers at 60% of their mature weight by 15 months of age.

“We want our heifers to be well grown so that when it comes to mating they are at peak fertility and will conceive and calve down early in the herd.

“By having heifers at 60% at 15 months, the heifer will have hit puberty and will have had a few practice heats before she hits the bull or the AI technician,” she said.

This target is important, she said, as heifers that are 10% below this target coming into the herd will have lower milk solids production – in the order of 16kg of milk solids per lactation.

3. Body Condition Score

Voogt also highlighted the importance of Body Condition Score (BCS) for hitting six-week in-calf rates.

“Body Condition Score at calving is very strongly correlated to Body Condition Score at mating, and it is the key driver of the number of days until first cycle.

“If cows are thin, they will take longer to start cycling and this will increase the number of non-cycling cows in the herd,” she said.

Under Irish conditions, farmers should aim to have their mature cows at a BCS of 3.25 at calving, while heifers need to be have a score of 3.5.

Fat cows may also be prone to reproductive failure, she said, and farmers shouldn’t have more than 15% of their cows outside of these BCS targets.

Dairy cows

4. Heat detection

Heat detection is also an important factor in driving six-week in-calf rate, she said, and farmers should take special care when it comes to identifying their bullying cows.

In a New Zealand scenario, approximately 25% of farmers can improve their heat detection management.

We don’t want to miss any heats because if you miss a cow that’s on heat there is no chance of getting her in-calf.

She also recommended the use of heat detection aids for the second round of mating, as many farmers will become fatigued after the initial burst during the breeding season.

ornua, superlevy, Irish milk, Aurivo

“Heat detection fatigue can really set in in the second round, so you need to be aware of getting those returns from first service.

“There is a whole range of different options available to optimise heat detection,” she said.

However, she said that whatever aids farmers choose to use, the best heat detectors are the farmer’s eyes and brain.

5. Is your bull ready for breeding?

Service bulls need to be fit for purpose, in good condition and disease free, so that they can hit peak fertility to get cows in-calf.

“If a bull runs a fever it takes two months for his sperm to come back to full motility. If he gets sick you need to consider getting a replacement bull.”

Along with healthy bulls, farmers also need to ensure that they have enough bulls to cover the amount of cows in their herd, as operating with one bull can be a high risk strategy, she said.


6. Practice your AI technique

It is always a good idea for DIY AI technicians to do a refresher course to ensure that their technique is up to scratch.

Farmers only get a chance to AI their cows during one period on the year, you have two months of breeding and you have ten months in the year when you are not even practicing it.

“It is a good idea to do a refresher course every couple of years to ensure that you are up to the job,” she said.


7. Avoid building up infertile cows and non-cycling cows

The fertility expert also advised farmers to avoid building up a herd of infertile and non-cycling cows.

“The best way to manage non-cycling cows is to not have them in the first place,” she said.

“Non-cycling cows come in two forms, the ones that really aren’t cycling and the ones that are cycling but were missed at breeding.”

Ideally, she said, farmers should identify the reasons for non-cycling cows on their farm, these often include thin, sick and late calving cows.

And based on this information, farmers should but a plan in place to deal with such cows in the following year’s breeding season.

8. Cow health

Cow health also plays an important role in achieving a six-week in-calf rate on farm, she said, and farmers should make note of any cows that were sick or experienced difficulties at calving.

This will allow farmers to be fully aware of the potential reduced fertility of these cows and to put a plan in place to ensure that they are adequately dealt with.

These cows could be lame, had calving difficulties, suffered from a disease outbreak or were low in minerals such as Selenium or Iodine.