There are big advantages of using AI on maiden heifers. Because heifers are the youngest animals in the herd, they should also have the highest genetic merit.

So breeding from heifers will speed up genetic gain. Using easy-calving AI bulls on heifers will also reduce the risk of calving difficulties and health problems after calving.

The disadvantages of AI on heifers is that heat detection and carrying out AI is time-consuming compared with running bulls with heifers.

However, a number of synchrony programmes are available that maximise the number of heifers served to AI, and minimise the workload involved.

Prostaglandin

This is probably the most successful synchrony programme for heifers, but it does involve some heat detection.

Heifers should be served to standing heat for seven days. Heat detection aids such as scratch cards should be used to help identify the heifers that are on heat.

After seven days, heifers not yet served should be injected with 2cc of prostaglandin (PG). Most of these heifers should come bulling 36 to 72 hours after getting the PG and should then be served.

The target is to have around 70% of heifers pregnant after 10 days of breeding

The advantage of this method is that it condenses the heat detection period from 21 to 10 days. Provided that the heifers are cycling, submission rate will be high and conception rate will be reasonably high too.

The target is to have around 70% of heifers pregnant after 10 days of breeding. Bulls can then be released with the heifers to pick up repeats.

For PG to work, there must be a functional corpus luteum present on one of the ovaries.

The corpus luteum is what is left of the follicle from the last cycle and is present from days six to 16 of the animal’s cycle.

So at any one time, provided that they are cycling, only about two-thirds of maiden heifers will respond to PG.

With this in mind, another option is to give heifers two shots of PG 12 days apart, with the second shot given two days before mating start date.

Most heifers should then come into heat in the first five or six days of breeding. If desired, bulls can be removed from days 18 to 27 if repeats want to be inseminated.

Fixed-time AI

All prostaglandin-based treatments involve some level of heat detection. Heifers can be served using fixed-time AI, which removes the need for heat detection.

These protocols use a progesterone device.

They are more expensive and involve a lot of handling of heifers and injections prior to being served, so good facilities and plenty of help is a requirement.

There are two options for using fixed-time AI. One option is to insert progesterone device and five days later give an injection of PG and remove the progesterone device.

Seventy-two hours later, give an injection of GnRH and AI.

The other option is to insert the progesterone device and give an injection of GnRH.

Five days later, remove the progesterone device and give an injection of PG.

This protocol will cost around €30 per animal

Twenty-four hours later, give a second injection of PG. Forty-eight hours later, give an injection of GnRH and AI.

Conception rates are said to be higher when using the second protocol, but it is more expensive.

This protocol will cost around €30 per animal. GnRH is a hormone that times the release of an egg, making fixed-time AI more successful.