Sexed semen – not for every cow

Teagasc studies conducted in 2018 and 2019 on Sexed Ultra 4M sexed semen on commercial farms found that conception rate was reduced when sexed semen was used. On average over the two years, the conception rate with sexed semen was 50%, while it was 61% with conventional semen. This 18% drop in relative conception rate represents a big cost at farm level. Using sexed semen across a herd would undo a lot of the fertility gains brought about by EBI over the last 20 years as it would lead to a more spread out calving pattern.

However, in both studies, some herds had a conception rate comparable to or better than conventional semen. The reasons for this are not yet known but offer a glimmer of hope for sexed semen.

Speaking at a recent series of information meetings, Tom Baker from Eurogene AI says that he knows plenty of farms that use sexed semen and get good results.

In fairness to Eurogene/LIC, it is the only AI company that has made any substantial effort at making sexed semen available in their top EBI AI bulls for the 2020 season. While it is in its interest to sell these straws, other companies are lagging behind in their offering. Sexed semen will never take off if only mediocre bulls are available.

If the difference in conception rate between sexed and conventional semen is reduced and if the top bulls are available sexed then it is no-brainer for Irish farmers to use more sexed semen to generate replacement heifers. There are, of course, some big challenges around this;

Firstly, we need to move away from the model of having one bull at the top of the active bull list as that is driving demand towards one animal. If bulls could only be sold as part of a pack there would be more genetic diversity and less reliance on a small number of bulls which are unlikely to ever be available sexed.

Performance

At the moment, we can’t tell how a bull’s semen will perform after being sexed. We know that some bulls are not suited to being sexed as the sorting process affects the sperm differently. Is there a genetic marker for this or can one be generated? This would give farmers confidence that bulls in their sexed semen pack are suitable for sexing.

The next issue is cow selection and this is all in the farmer’s hands. The objective is to use sexed semen where there is a good chance of conception. This will reduce cost as sexed straws are more than twice the price of conventional.

On most farms, the most suitable animals for sexed semen will be maiden heifers, as their relative conception rates are usually about 17% higher than cows anyway. Also, different methods of synchronisation mean that nearly all heifers can be bred within the first 10 or 11 days of breeding. Only heifers that are at target liveweight and in good body condition score should be considered for sexed semen.

For milking cows, you will need to be more selective with the cows for sexed semen. The following points are suggested by Teagasc and others when using sexed semen;

In all cases, later than normal insemination is advised when using sexed semen. Teagasc recommend that animals should be inseminated 14 to 20 hours after the onset of heat. This means that if using once a day AI or even twice a day AI it will not be possible to serve all animals that come into heat with sexed semen, even if she fulfils the criteria outlined above. Therefore, sexed semen should only be used alongside conventional or beef semen.

Read more

Sexed semen results disappoint

Sexed semen from New Zealand available this spring