There is a clear correlation between the use of sexed semen for producing replacement heifer calves and the use of beef AI to produce higher beef value calves from the dairy herd. Farmers are recognising that the benefit of sexed semen is not to have loads more heifer calves, but instead to be able to select what cows you want a heifer from and then to use beef AI on the rest.

The benefits of such a policy are clear, with faster genetic gain in the dairy herd from being able to breed heifers from high-EBI cows, plus having a more saleable beef calf compared to a dairy bull calf, whether he be a Holstein Frieisan or a Jersey crossbred.

With 800,000 cows to be genotyped this summer and their calves to be genotyped next spring, the actual beef value of calves will be readily identifiable through the commercial beef value (CBV).

Each genotyped calf will have a CBV and this will be available to buyers on the mart boards or as a printout from the ICBF website. Calves that haven’t been genotyped won’t have a CBV because their parentage won’t have been verified. Therefore, there is a strong incentive for dairy farmers to use high-beef-merit AI bulls on the cows they don’t want a dairy heifer calf from and to use genotyping to prove that the calf is out of those high-beef-merit AI bulls. So if producing a more saleable calf is the benefit, what are the downsides? For me, there are a few disadvantages to this approach.

Firstly, sexed semen has lower conception rates than conventional semen and so should be used carefully. However, the bigger issue is the risk of harder calvings and longer gestation lengths, as a result of using more beef bulls and the impact this is going to have on cow fertility, so a degree of caution is advised.

Beef bulls

Producing a saleable calf should not mean jeopardising the health of the cow or indeed the calf. Almost as much effort should go into choosing beef bulls for dairy cows as for choosing the dairy bulls. The CBV will be expressed in terms of a euro figure and also star ratings, with a five-star animal in the top 20% and a one-star animal in the bottom 20% for CBV.

The objective is to have as many four-and five-star beef calves as possible. The CBV for a beef animal is derived from the contribution of genes it has received from its parents. On the dam side, this is comparable to the value for beef sub-index in the EBI, with a few slight alterations. On the sire side, the value comes from the beef value in the dairy beef index (DBI).

According to Alan Twomey of Teagasc, using a beef bull with a beef value in the DBI of at least €80 will ensure, in most cases at least, a four-star calf. This is shown in Table 2, where the differing beef sub-index values in a herd’s EBI are reflected in different CBV values for the calf. This shows that dairy herds with a low beef sub-index in EBI will need to use higher CBV bulls in order to breed four- and five-star bulls.

Looking at the beef bulls in the DBI active bull list for 2023, the top 20 bulls have an average beef value of €119, meaning that the calves from these bulls, when crossed with the typical Irish cow, will easily generate four- and five-star CBV calves.

Essentially, almost all of these bulls are good bulls from a beef value perspective and are all relatively easy calving on cows and relatively easy calving on heifers. There is greater variation when it comes to gestation length, however, with some bulls having a gestation length proof of -4.9 days, while others have plus three days.

The number one bull, Kealkil Prime Lad (AA4743), has a gestation lenght of -3.5 days and yet has an excellent beef value of over €100. Contrast him to the much scorned Angus bull KYA with a gestation length of -4.9 days but only €69 for beef. OK his calves might come quicker, but they’ll take longer to get to the 50kg sale weight and still won’t be as good as calves from AA4743.

That said, farmers need to be wary about what beef bulls they use and don’t repeat mistakes made in the past with long gestation length and hard-calving bulls wreaking havoc on cow fertility.

Sexed semen

A new study conducted by ICBF into the on-farm performance of sexed semen has shown that the average conception rate to sexed semen is now at 59% compared to 64% for conventional semen. Relatively speaking, sexed semen is now 92% as good as conventional semen when it comes to conception rate. This is good news as previous research showed it to be 84% as good as conventional semen for conception rate.

This new analysis looked at actual conception rate on thousands of commercial dairy farms between 2018 and 2022. The analysis was based on over 1.82m conventional inseminations and 86,000 sexed semen inseminations.

All inseminations were completed by AI technicians and pregnancy was determined by an actual birth event, nine months after insemination. There were no DIY AI inseminations included in the analysis.

The results of the field data were statistically analysed, with important factors such as year, herd, lactation, days in milk and cow genetic merit all accounted for in the model. Results from the study are summarised in Table 1.

Margaret Kelleher from ICBF says that the results highlighted the significant herd-to-herd variation in the performance of sexed semen;

“Like 2013, the difference in herd performance was striking, with the top 10% and bottom 10% of herds achieving pregnancy rates for sexed semen of 73% and 40%, respectively, with an average of 59%,” she said.

This highlights the importance of selecting cows most suitable for sexed semen, namely younger cows in good body condition, calved more than 50 days and with no health issues.

It also highlights the importance of correct technique when inseminating with sexed semen.