Coming into the June Bank Holiday weekend, a lot of farmers often stop using dairy artificial insemination (AI), and just let the stock bulls clean up the rest.

However, before the stock bull gets going or you make the switch to dairy-beef AI straws, it is important to ensure you have enough dairy replacements in the pipeline.

The rapid uptake of sexed semen in the past number of years has led to a shortage of dairy replacement heifers coming through.

With the price of dairy-beef calves over the last two years, it is very tempting to go all out on dairy-beef straw or stock bulls now.

But the prices available for quality dairy calves has not been anything to snub your nose at either, meaning you are not going to lose out on a whole pile of cash by breeding those extra few contingency heifers.

Therefore farmers should be aiming to breed a few more heifers this year to ensure they have a respectful replacement rate.

If this is the case on your farm and those extra replacements have not yet been bred, it needs to be done in the coming days.

Calving down heifers late can be a costly exercise due to the fact they need to be pushed harder to be calving down in early spring two years later.

Where there are signs of heifers not coming into heat or any problem cows on the farm, these animals need to be checked by your vet to rectify the underlying issue so a decision can be made.

Cut-off for dairy AI

Every farm has a different suitable cut-off date for dairy AI, depending on how it wants the calving season structured.

For example, farms in heavy soiled areas may have a later calving start date and a relaxed calving pattern, while free-draining farms may calve down early and keep things nice and compact.

Either way, it is important to strike a good balance as calving too early can be costly on extra supplementation needed, while calving too late can be costly in terms of lost milk production.

That is why it is important to have your decisions made now of when to finish the breeding season and when to finish breeding with dairy AI, with any of the cows not meeting these cut-off dates going into the culling strategy.

With a gestation length of 283 days, a guideline of expected calving dates based on the serve dates is provided in the table below:

Ideally, you want your replacement heifer calves calved down in the first three weeks of the breeding season, but if you intend on breeding a few more to dairy AI in the coming days, the cut-off point should in the first week or two of June.

In terms of the overall breeding season, whether it is stock bulls or beef AI used after dairy AI, most dairy farmers should aim on concluding their breeding season between July 1 and July 15 to have calving well wrapped up by mid-April and minimise any late calvers.

Bull power

A good rule of thumb to follow is a mature bull should cover approximately 30 cows within three weeks, while a young bull will cover roughly 10 heifers every three weeks.

That been said, activity can ramp up from day to day and leave bulls overworked, especially if there are a lot of repeats within a short window.

Therefore, there should ideally be more bulls than required on farm, or keep AI going in conjunction with the bull team.

The number of bulls needed is going to vary throughout the breeding.

Based on a 100-cow herd, the following amount of bulls should be used:

In the above scenario, AI is used in the first round with good results all round, meaning using three bulls will be enough.

If a synchronisation is used, it is best to AI the first round of repeats, as the numbers will be in excess of what the bulls will be capable of physically dealing with in a short space of time.