JSR Genetics - Semen volume and concentration: how much to use and does it matter?

By Dr Grant Walling and Dr André Maldjian, JSR Genetics

With new technologies for artificial insemination, a key question is often "What is the correct volume and concentration of a semen dose to achieve optimal performance?"

For AI to be successful, the physical displacement of the uterus is crucial for effective transport of the semen to the oviduct. For this to occur, it is essential to mimic the naturally large volume of a boar ejaculate.

Scientific reports highlight external factors that will influence the optimal sperm number in an AI dose. Most breeding companies despatch insemination doses containing 2.2-3 billion total spermatozoa. Table 1 indicates fertility levels in sows inseminated with varying sperm doses. One billion sperm inseminated with a conventional catheter gave poor results (Watson et al., 2001).

In Denmark, insemination doses of 2 billion spermatozoa in 80-85ml have given good fertility results in terms of farrowing rates (87.6 %) and litter size (14.1). The Danish National Committee for Pig Production then investigated decreasing to 1 billion spermatozoa using a double bag, allowing for flushing the insemination catheter after use. The final volume of insemination was 80ml in both the lower dose and control (2 billion).

Farrowing rates were similar for the two different doses but litter sizes were smaller when using 1 billion spermatozoa.

Post-cervical insemination appears an extremely useful technology when lowering the insemination dose. This does, however, raise health concerns, as the risk of cervical uterine injury and uterine infection are greater, especially if poorly trained technicians carry out the procedure.

New catheters, allowing semen delivery in the uterine horns rather than in the proximal cervix, have been developed over the last few years. In a German study, a dose of 10 million spermatozoa in 20 ml, inseminated in the distal part of the uterine horn, gave similar farrowing rates and litter sizes compared to traditional AI.

Surgical techniques allow for even lower insemination doses (about 1 million sperm in 0.5 ml). Studies have shown that surgical inseminations of synchronised gilts with as little as 10 million spermatozoa in 0.5 ml deposited near the utero-tubal junction of each uterine horn achieved fertility levels comparable to that obtained with 3 billion spermatozoa with conventional AI.

These options, however, are largely impractical in conventional commercial pig production.

So why do breeding companies use 2.2-3 billion spermatozoa a dose and a volume of 70 to 100 ml? Because it is a robust way to achieve good fertility levels whilst coping with deficiencies due to inaccurate insemination timing, inferior technique or poor quality of the sows - and still makes semen affordable.

References

Watson et al. 2001. VIIth International Conference on Pig Reproduction, University of Missouri, p135.
Gall 2002. Journal of Animal Science 80 (Supplement 2), p 46

Appeared in International Pig Topics (June 2006)