Unlocking the genetic potential of sows and boars

”Since the introduction of Artificial Insemination (AI) on intensive pig farms, it certainly proved its value as an effective tool to hasten the spread of superior genetic material. Even using existing AI techniques we have seen both improved sow fertility and litter size over the last few decades. In Canada for example, where I am currently based, we have increased average litter sizes by about two piglets per litter since the adoption of AI. However, we know that from a fertility viewpoint, some superior boars have the potential to produce as many as 14-15 piglets per litter and in the same boars studs other boars may sire litters of only nine or ten pigs if used in single-sire matings. The problem is that this genetic potential for fertility is not transferred to improved technical results at farm level because sows are invariably inseminated with a so called combined (pooled) semen doses, created by combining two to six boar ejaculates. The ‘magic’ of the superiority that best boars is then lost and their fertility is ‘averaged down’ in pooled semen doses.

 

There is great uncertainty in multipleboar pools of semen about the paternity of the pigs produced: Therefore, the genetic index of superior sires for the performance of slaughter generation progeny may not be realised. I believe that this pooling of semen – as described above – together with the practice in many countries of using large numbers of sperm cells per AI dose (three billion is the accepted ‘gold standard’) limits the genetic impact of superior sires. These limitations can be addressed in different ways; 1. Use of single-sire semen doses and 2. The use of reduced numbers of sperm for each insemination. Conventional semen analyses generally provide quantitative information on the semen itself but do not necessarily have any clinical value in predicting sow fertility and litter size among relatively fertile boars. Hopefully we will one day create new sperm function parameters/ markers, which can be used to better select boars on their individual potential. This will assist in getting rid of the poor performing boars and not even consider using them in any breeding programme.

 

Another solution that the sector needs to address is using less sperm cells per insemination dose. The option to reduce sperm doses without affecting productivity at sow level (farrowing rate and litter size born) does not automatically apply to every boar, the so called ‘sensitivity curve’ needs to be kept in mind. This means that some boars might yield the same results with 1 billion cells compared to other boars that need a higher amount of cells to transfer their genes effectively. Again, more data on individual boars is critical. With these data we can not only lower the insemination dose used in our more fertile boars but we can also hope to lower the number of inseminations per sow bred from 2.5 to only one in the future by using single, fixedtime, insemination technologies.

 

At the University of Alberta we are currently looking to implement applied research projects at commercial level that will link techniques for fertility evaluation of individual boars with a gradual reduction in the number of sperm per dose and the number of inseminations per sow bred. Linking this to our knowledge about the genetic potential of boars and sows available, we can then step up the whole genetic value of the breeding herd. I think the farmer can earn up to one additional dollar per piglet weaned by adopting this approach. Investing more in improved boar evaluations and more advanced AI technologies is one realistic way forward to further improve the competitiveness of the pig industry.”