Get the key ingredients right and the six-week-in-calf rate is far more likely to be on target

The mating season is here and getting cows in-calf quickly will be key to achieving a good calving pattern next year, remembering that routine inductions will not be allowed from June 1.

Heat detection, pre-mating heats and bull management are key ingredients for a successful mating - get these right and the farm's submission rate and six-week-in-calf rate will benefit.

Most herds in New Zealand achieve in-calf rates well short of industry targets and their calving pattern will be at risk if nothing changes.

The aim is to get the best in-calf rate - the rate at which cows become pregnant throughout a total mating period of 10 to 12 weeks.

This requires both a high submission rate of 90 per cent and a high conception rate of 60 per cent.

These two drivers of reproductive performance require the herd to be in a naturally fertile state, as indicated by a high proportion of cows (85 per cent) having had one or more pre-mating heats. It also requires heat detection systems used on-farm to be efficient and accurate, so few heats are missed and few heats "invented".

Farmers should ask themselves: "Will the cows resume cycling at the required rate pre-mating and will a high proportion of them conceive to artificial breeding (AB) insemination in the first six weeks of mating?'

So, what can be done now?


The easiest way to spot cycling cows is to do pre-mating heat detection.

The period before mating is an opportunity to practise heat detection, checking for cows not on heat and anticipating when they might next come on heat. Team training should be organised at this time, with the most experienced person helping the less experienced team members to interpret signs of heat.

Use tail paint to pick out cycling cows. Use one colour tail paint to start, then a second colour as cows cycle and lose their tail paint. Within two weeks about half the cycling cows will have been identified. At three weeks, cows with the original colour are the non-cyclers.

Calculate the herd's pre-mating cycling rate (InCalf Book, page 83) for the percentage of cows showing signs of heat before mating begins. If cycling is less than 75 per cent by 10 days before the planned start of mating, heat detection has not been fully effective or there are too many non-cyclers, or both.

At that stage it is time to seek advice and consider which options are available to improve heat detection during AB and treat non-cycling cows.


The best heat detection starts with careful planning, good observation and the effective use of detection aids.

Being able to interpret cow behaviour and other signs is critical, along with good record-keeping and training for those doing heat detection.

Start by reviewing the farm's heat detection skills.

Are they up to scratch and does everyone know what to look for when detecting cows on heat? Then, decide which combination of aids the farm will use: tail paint, heat mount detectors, activity meters and heat synchronisation.


Tail paint is an inexpensive and effective way to detect cows on heat.

Apply tail paint to all cows just before the start of mating, touch it up at least weekly and check for cows with rubbed or broken tail paint during milking.

Re-checking tail paint for rub marks immediately before each cow's insemination will avoid inseminating cows not on heat.

To help identify cows not yet inseminated or those only showing weak signs of heat, reapply a different coloured tail paint to recently inseminated cows once other cows no longer try to mount them.


DairyNZ's InCalf programme shows that heat detection rates are higher in herds using heat mount detectors. The detectors can be particularly effective on farms with less skilled staff checking cows and when used with paddock checks for heat.

Applied to the cow's backbone, the detectors will become brightly coloured and easily recognised. Again, heat mount detectors should be applied just before mating starts, then monitored for activation and removed at insemination. Until the end of the AB period, the detector should be replaced after insemination, when the cow is no longer being mounted. Replace detectors if damaged or loose.


Give bulls time to adjust


Good bull management ensures they are well adjusted to their environment before mating.

Move bulls to the farm two to three months before they are required for work. Buy bulls from the same mob and split them into two teams to rotate them - half resting and half working - to reduce fighting.

The in-calf bull management practices component at has a thorough checklist about bull management: search "herd assessment pack tools".

Review your in-calf fertility focus report performance after week six (figure 1) to find out how big the performance gap is during bull mating. Also check the shape of the new graph (figure 2) on the version two detailed fertility focus report. This often shows a drop in the rate cows are becoming in-calf during bull mating.