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Reproductive Physiologist Stephen Butler is leading dairy cattle reproduction research at Teagasc to increase female calf births and improve the value and sustainability of dairy and beef farms.

TResearch Autumn Winter 2021Dairy farming is Ireland’s most profitable agricultural enterprise. Research plays an essential role in improving its productivity and sustainability, and much of Teagasc’s work is done to help support farmers and their success.

The breeding and genetics of cattle is one such area of interest. In most dairy herds, 70% of calves born are destined for beef production. But due to genetics, half of these calves will be male dairy calves. Males that have dairy traits are of low economic value for beef farming, and any animal that has low economic value is a potential welfare concern.

Back in 2013 a project was launched at Teagasc Moorepark to reduce the number of male dairy calves born into Irish dairy herds. This ongoing project looks at how sexed semen (specially processed semen that removes ‘Y’ chromosome sperm cells which lead to the birth of a male) could resolve the issue. It has made some exciting developments over the years and sexed semen has gained increasing popularity in Ireland as a result.

The project is led by Teagasc Reproductive Physiologist Stephen Butler. Stephen started his journey with Teagasc over two decades ago, when he completed research for his Masters in Animal Nutrition at Teagasc Moorepark. A subsequent opportunity to study at Cornell University via the Teagasc Walsh Scholarship programme saw Stephen swap Ireland for New York where he completed his PhD in Physiology of Reproduction. He returned to Teagasc in 2004 and has been here ever since.

Stephen, why is sexed semen of interest to dairy farmers?

The genetics of cattle semen mean that the chances of a male or female calf being born are roughly equal. Sexed semen increases the percentage of sperm cells containing the desired sex to around 90%. This means that in dairy breeding, 90% of pregnancies that take place after insemination with sexed semen will be female calves.

How has your research on sexed semen developed over the years?

In total, we have conducted three large-scale field trials in collaboration with the Irish Cattle Breeding Federation (ICBF), University College Dublin (UCD), Irish artificial insemination (AI) companies and Sexing Technologies – a leader in sexed semen production.

The first was in 2013, when Sexing Technologies set up a temporary lab in Teagasc Moorepark to run a field trial to evaluate their sexed semen product. In the years since, improvements to the technology used have been made – most notably, sperm cell numbers have increased from two million to four million per straw (a device semen is stored in). Because of this improvement we did extra trials on the product, including testing AI after observed oestrus (when the cow expresses sexual receptiveness behaviours) and fixed-time AI (when the timing of ovulation is controlled). These trials have allowed us to identify some guidelines for the most effective use of sexed semen.

Sexing Technologies has recently re-established a sexed semen lab at Teagasc Moorepark. This lab opened in November 2021, and provides a semen sorting service for the Irish AI industry.

What are the benefits of having this lab in Ireland?

It’s a major cause for celebration because it will kick-start greater usage of sexed semen and, importantly, the number and quality of bulls available sexed will increase.

Before this, Irish AI companies sent bulls overseas for the process, usually to the UK or the Netherlands. But biosecurity and quarantine requirements meant they didn’t send a large number of bulls or the best bulls. Now, with a local lab, it’ll be easier to get sexed semen straws produced from as many first-choice bulls as required, because they don’t have to travel abroad.

What benefits does sexed semen have for farmers?

Sexed semen has many advantages for farmers, including the potential for increased genetic gain by inseminating only the best females with sexed semen.

Sexed semen use would typically be limited to the first two to three weeks of the breeding season. This is an advantage because it streamlines replacement heifer management and gives them the maximum amount of time to grow before they become lactating cows. 

The cows (and heifers) that are not suitable for producing replacements can receive beef semen. The calves born are more attractive to beef farmers and can help to displace suckler beef production – an emissions-intensive system – and improve the sustainability of beef production.

What are the challenges of using sexed semen?

The sexing process is damaging to sperm cells. Pregnancy rates are lower, so it needs to be used carefully to achieve good fertility outcomes.

Another challenge is the cost. Sexed semen is more than twice the price of a conventional semen straw. Whilst the initial cost is higher, however, it’s repaid once the calves are born thanks to their value.

It’s also likely that the technologies and procedures used will continue to improve as investment into this area increases, resulting in improved pregnancy rates and lower costs of production.

What’s the focus for your research over the next 12 months?

We have an exciting project planned to examine the use of sexed semen to generate IVF embryos in order to accelerate genetic gain in both dairy and beef breeds. Sexed semen is a very useful tool in that process as it allows breeders to decide in advance the preferred sex of the embryo. 

Up close and personal

What’s your favourite animal?

It has to be man’s best friend – a dog. They’re always happy to see you!

If you hadn’t ended up in agriculture, what other job would you have wanted to give a go?

Centre back for Manchester United and Ireland, playing alongside Roy Keane and Denis Irwin during the glory years!

What are you most proud of professionally?

I’m about to complete my final year as Senior Editor for the physiology section of a leading journal in my area of work. It was a real honour to get the invitation and it’s been a very rewarding experience.