Additional value of computer assisted semen analysis (CASA) compared to conventional motility assessments in pig artificial insemination M.L.W.J. Broekhuijse a,b , E. Šoštaric ´ c , H. Feitsma d , B.M. Gadella a, * a Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands b Varkens KI Nederland, Deventer, the Netherlands c Departement of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands d IPG, Institute for Pig Genetics B.V., Beuningen, the Netherlands Received 8 December 2010; received in revised form 3 May 2011; accepted 4 May 2011 Abstract In order to obtain a more standardised semen motility evaluation, Varkens KI Nederland has introduced a computer assisted semen analysis (CASA) system in all their pig AI laboratories. The repeatability of CASA was enhanced by standardising for: 1) an optimal sample temperature (39 °C); 2) an optimal dilution factor; 3) optimal mixing of semen and dilution buffer by using mechanical mixing; 4) the slide chamber depth, and together with the previous points; 5) the optimal training of technicians working with the CASA system; and 6) the use of a standard operating procedure (SOP). Once laboratory technicians were trained in using this SOP, they achieved a coefficient of variation of  5% which was superior to the variation found when the SOP was not strictly used. Microscopic semen motility assessments by eye were subjective and not comparable to the data obtained by standardised CASA. CASA results are preferable as accurate continuous motility dates are generated rather than discrimination motility percentage increments of 10% motility as with motility estimation by laboratory technicians. The higher variability of sperm motility found with CASA and the continuous motility values allow better analysis of the relationship between semen motility characteristics and fertilising capacity. The benefits of standardised CASA for AI is discussed both with respect to estimate the correct dilution factor of the ejaculate for the production of artificial insemination (AI) doses (critical for reducing the number of sperm per AI doses) and thus to get more reliable fertility data from these AI doses in return. © 2011 Elsevier Inc. All rights reserved. Keywords: Sperm motility; Computer assisted semen analysis; Standardisation procedure; Fertility; Boar; Artificial insemination 1. Introduction One of the important parts of semen quality evalu- ation in human and different animal species is micro- scopic semen motility assessment. Traditionally, semen motility is assessed by a technician who scores by eye when looking through a phase contrast microscope. However, this practice gives rise to subjective interpre- tation of individual technicians (which in part also depends on the level of skill and training of the tech- nician). This technician-based variation in results makes it difficult to estimate the effect of sperm mo- tility on fertility traits. The method is not standardised and subjective. Moreover, it only allows discrete mo- tility scores (increments of 10%) only estimating the number of motile sperm [Broekhuijse et al, unpub- * Corresponding author. Tel.: +31-30-2535386; fax: +31-30- 2535492. E-mail address: b.m.gadella@uu.nl (B.M. Gadella). Available online at www.sciencedirect.com Theriogenology 76 (2011) 1473–1486 www.theriojournal.com 0093-691X/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.theriogenology.2011.05.040