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Three beef sires are better than one (Nov/Dec 22)

Not all beef bulls are equal. So what is the ideal beef semen for use on dairy herds? CRV shares the latest non-return percentage figures for its mixed Belgian Blue semen.


The number of beef-cross calves born on dairy units continues to rise. AHDB figures show that 10 years ago a third of calves born were registered as beef animals, but in 2021 this had increased to 50%. So cattle breeding companies are paying more attention to the quality of the beef sires they supply.

In early 2022, CRV and the Belgian Blue Group (BBG) began a study on mixed semen collected from Belgian Blue bulls used in commercial breeding. The results of a field test have confirmed that combining three bulls’ worth of semen in one straw can increase the non-return percentage rate by 4.2%.

This is not a new idea. Mixing multiple bulls’ semen can increase its fertilisation capacity. “In the US, Canada, Australia, New Zealand and the UK, many producers have worked with mixed semen for some time. And we’ve gained a lot of experience of producing this mixed semen in Canada in recent years,” says Simon Noppen from Belgian Blue Group (BBG), which supplies semen that’s available through CRV.

Mixed semen

“Until 2021 the use of mixed semen was banned in the EU under pan-EU veterinary legislation. When we learned that these regulations were going to be abolished, we started looking into the feasibility of producing mixed semen at our own premises in Ciney, in Belgium,” he adds. “We saw an opportunity to develop a product with even higher conception rates than conventional semen.”

Figure 1: Mixed semen: combining three Belgian Blue bulls' semen in one straw

Following insemination, spermatozoa remain viable for a brief period. “The duration of this period differs from bull to bull and, as a result, the availability of live sperm at any time during the cow’s fertility cycle varies from bull to bull,” explains Marleen Broekhuijse, who is a CRV-affiliated researcher specialising in semen quality. “Mixing multiple sires’ semen increases the likelihood that enough sperm will be available for conception at the right time. And cows will be more likely to fall pregnant,” she says, giving a plausible biological explanation for the positive effect of mixed semen.

Conception rates

So, theoretically, mixing multiple bulls’ semen looks promising for producers looking to improve conception rates. “But before we market a new product, we want to be sure that what works in theory also works in practice,” adds Mr Noppen.

That’s why he conducted a field test, with CRV, where 3,000 dairy cows were inseminated with mixed semen, containing semen collected from three Belgian Blue bulls used for commercial breeding.

“All the semen included in the mix meets our highest quality standards, and we will continue to keep that quality up in the future. If a sire’s semen does not meet our quality standards, it will not be used in mixed semen,” he stresses, dispelling concerns that mixing semen is a way to ‘use up’ lower-quality semen. “Producers who purchase the semen we produce, whether it be mixed or conventional, can be assured that the semen has good fertilising capacity.” To be able to conduct their field test, CRV researchers used a unique insemination registration system. “For each batch of straws collected from each bull, we know exactly how many of the inseminated cows were offered for re-insemination within 56 days after the initial insemination,” says Dr Broekhuijse.

“This data is corrected for factors that may affect the conception rate, meaning we always have a reliable picture of the development of all our bulls’ non-return percentages,” she adds.

The conception rates in cows inseminated with mixed semen are extremely good. “At day 56 following insemination, the mixed semen available from BBG and CRV has a non-return percentage that is 4.2% higher than the average insemination rate when using semen from just one sire. This means that in every 100 inseminations, more than four more cows will fall pregnant following insemination with our mixed semen compared to insemination with semen collected from a single sire with average fertilisation capacity.”


calving ease breeding value


no. of daughters

no. of herds

Intrepide de Cras Avernas










Elk 41 van de Plashoeve





Table 1: Calving ease breeding value and reliability of CRV's Belgian Blue sires

Belgian Blue sire calving-ease performance

How many difficult calvings can producers expect when using a Belgian Blue sire? On average, the incident of dystocia when using Belgian Blue bulls on first-lactation heifers or Holstein cows is approximately 9%, according to figures from CRV’s animal evaluation unit.

Belgian Blue sires have an average calving ease index of 100. The higher the sire calving-ease index, the lower the percentage of problem births. For example, Belgian Blue sire Elk 41 van de Plashoeve has a calving-ease index of 131, which corresponds to a 5% rate for difficult calvings.

The Belgian Blue sires offered by CRV are reliably tested. Elk 41’s calving-ease index is based on figures from 5,000 daughters, resulting in a reliability of 89%.

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