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

Increasing fat and protein percentages in dairy cows can be difficult to achieve, but by setting goals and sticking with them it is possible to pull off.

It has taken Mervyn McRoberts over 12 years of focussing on improving percentages in his herd to get him to where he is today.

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

Increasing combined fat and protein

Improving the genetics of his herd and focusing on forage quality has resulted in significant improvements within Mervyn’s herd.

Current average production from the herd is 9,600L/cow from 3t of meal.

For fat, the herd is averaging 4.40% and for protein, 3.51%; this equates to 782kg of combined fat and protein.

Mervyn McRoberts

Compared to the herd’s first benchmarking figures which were taken in March 2008, combined fat and protein has increased by 182kg.

In 2008 the figures for the herd were 7,600L/cow from 2.5t, with average fat of 4.39% and protein of 3.31% – which equated to 600kg of combined fat and protein.

Sire selection

When it comes to sire selection the main focus on Mervyn’s farm was to use bulls with high fat and protein percentages.

Mervyn wants a cow that is able to do her weight in combined fat and protein so is looking for a cow between 650-700kg – which also has capacity.

A cow that is good on her feet is also important with the herd going to grass in the spring once ground conditions allow.

Mervyn relies heavily on advice from Ivan from AI Services when selecting bulls, with his knowledge of the bulls being vital to the farm’s success.

Although selecting sires for fat and protein has been important to Mervyn, selecting bulls to increase production has not been.

Sires are generally selected that are around 300kg, with the litres in the herd increasing by 2,000L since 2008.

Mervyn believes that better comfort for the cows, better feeding and improved genetics has all played a role in this.

When milk prices are good, combined fat and protein being high is not as important, but when milk price is low an extra 10% on top of your milk cheque for good milk quality is, according to Mervyn.

It takes time to improve, and improving has been a focus for this herd for so long that Mervyn is not going to let it drop now; the focus on fat and protein over litres is to continue.


Since 2010 the herd has been using 100% artificial insemination (AI), with the aid of a heat detection system.

A major focus has been placed on compacting the calving pattern for the herd and getting more cows calved in the autumn period.

In 2008, 50% of herd would have calved before Christmas with the remaining 50% calving between January and May.

In 2022, 80% of the herd calved between the last week of August to the end of October, with the remaining 20% calved by the end of January.

The average Profitable Lifetime Index (PLI) for the herd is £267, with the maiden heifer having an average PLI of £500 and the calves having an average figure of £522.

Although PLI is a good guide, Mervyn doesn’t heavily rely on it when it comes to his breeding decisions.

Mervyn said he will continue to focus on improving fat and protein in the herd, with that continuing to be the focus above everything else.