Breeding Series 2023 in association with Eurogene, LIC and AI Services

The main focus of Mervyn McRoberts’ breeding programme for the last 12 years has been increasing combined fat and protein kg/cow.

The Northern Ireland farmer has increase combined fat and protein by 182kg/cow to 782kg/cow, and his new target for the next 10 years is to reach 900kg/cow.

Mervyn farms near Ballinderry, Co. Antrim, and milks 120 Holstein Friesian cows in an autumn-calving system.


Going forward, Mervyn’s aim is to continue to increase the fat and protein percentages within the herd, while maintaining current milk yields.

He is also hoping to maintain and increase fertility levels within the herd, while also having an animal that suits his system and can eat large amounts of forage.

Mervyn McRoberts

The main focus when it comes to sire selection will be fat and protein, but other traits will be adjusted if, and when needed. This may include teat length and udder conformation.

Fertility is also important as the farmer has moved away from using a stockbull and is now using 100% artificial insemination (AI).

This has stopped cows that were due to be culled remaining in the herd and has also allowed for more selective breeding to further increase genetic gains.

For advice, Mervyn relies on Ivan from AI Services to ensure that he is using the best bulls for his herd.

Sexed semen

Sexed semen has already had a role on the farm for the last number of years, but Mervyn is planning to increase its use.

Ahead of the last year’s breeding season, the decision to go all in was made and 120 sexed semen straws were purchased.

All cows that were suitable for a dairy straw were serviced over the first four weeks of breeding, and beef straws were then used on the cows.

Another key area that Mervyn will be focusing on is having all of his replacement heifers calved in a short period of time.

This has allowed him to have a nice even batch of maiden heifers and the in calf heifers are “sitting like peas in a pod” he said, making the management of these heifers much easier.


The increased use of sexed semen has resulted in an increase in the amount of beef straws being used on the cows.

A mixed beef straw has been used for the last few years, with Mervyn believing that they are getting higher conception rates as a result.

A double Angus and Hereford straw has been used by Mervyn for the last number of years and the main criteria for selection is to have the easiest calving possible.

He aims to have the cow able to get back in calf six to eight weeks later.