By Alan Hopps, CAFRE
SEXED semen technology has been constantly evolving over recent years and its use in Northern Ireland dairy herds has increased rapidly as a result.
Relative conception rates (compared to conventional semen) has been claimed to be around 90 per cent. Thus, if conception rate to conventional semen is 40 per cent, conception rate to sexed would be 36 per cent.
A recent Teagasc trial found that a small number of herds actually achieved better conception rates with sexed semen than conventional. Some of the main points around achieving better conception rates with sexed semen are as follows:
n Sexed semen should be thawed and handled more carefully;
n One straw of semen should be used at a time if there are multiple animals to be served.
n The use of sexed semen on known problem breeders or cows that have had difficult calvings should be avoided;
n Animals to be bred should be restrained prior to thawing of semen;
n Sexed semen performs better when used around 18 hours after oestrus (peak heat), compared to about 12 hours for conventional semen. Heat detection monitors are now installed on many farms and these can help to better predict optimal timing of AI with sexed semen;
n The use of sexed semen should be prioritised on maiden heifers. These animals will be the best genetics in the herd and will have higher conception rates when compared to cows.
Sexed semen has the potential to produce a larger number of heifers in a herd when compared to using conventional semen. Dairy farmers should have a clear plan for cow numbers on their farm and only produce the number of replacements that they require. This will avoid a large number of unproductive stock on the farm. Cows not intended for breeding replacements can be bred to beef semen.
The use of mixed sire beef semen has the potential to improve conception rates by six to nine per cent when compared to conventional semen. This should allow overall herd conception rate (including sexed and mixed beef) to average out close to the use of conventional semen across the entire herd.
Sexed semen is generally more expensive than conventional. This coupled with a lower conception rate will be an extra cost for the dairy herd. The reduced number of unwanted Holstein bull calves on farm is one of the main benefits for sexed semen – especially when their value is compared to beef calves from the dairy herd. The dairy farm will thus have more beef calves to sell and this should more than offset the additional costs associated with sexed semen.
If a large proportion of maiden heifers are bred to sexed, this will also speed up genetic progress in the herd. Breeding the best animals in the herd to the best bulls has always been the route to the most rapid genetic progress.
Sexed semen in now a more reliable tool to allow dairy farmers to do this.