ELSEVIER SPERM FACTORS RELATED TO IN VITRO PENETRATION OF PORCINE OOCYTES J. Gadea’ and C. Matas Department of Animal Biology, School of Veterinary, University of Murcia, Spain Received for publication: November 16, 1999 Accepted: July 26, 2000 ABSTRACT This study was designed to evaluate the relationship between sperm factors and penetration capacity in an in vitro system with immature porcine oocytes. The sperm parameters evaluated in 145 ejaculates were volume, sperm concentration, total cells in the ejaculate, ATP content, morpho-anomalies, percentage of motile sperm cells, forward progressive motility (FPM), acrosome status (NAR), hype-osmotic swelling test (HOS), osmotic resistance test (ORT), eosin-nigrosin viability stain and sperm membrane integrity (DCF). Porcine oocytes (a total of 8738) were used to evaluate the capacity of the different sperm assays to predict penetration. Many parameters were found to be related to in vitro penetration ability; all conventional semen parameters, except sperm concentration and eosin- nigrosin staining, were significantly better in high (>75%) than in low penetration rates (~75%). When the ejaculates were preselected the number of significantly related parameters was lower. When studying all conventional semen parameters through a stepwise multiple linear regression analysis of seminal measurements, up to 72.3% of total variance of the penetration rate could be predicted. However, as many as 4 parameters were needed (FPM in fresh semen, folded tail, NAR in post-treatment semen and DCF) for accurate prediction. On the other hand, the multiple logistic regression needed 7 parameters to discriminate 83.88% of the cases correctly. In summary, the results from the present study showed that almost all studied parameters were significantly different for predicting penetration process attained or failed, but most of them were correlated together. These findings emphasize the complexity of sperm functions and the difficulty of assessing the fertilizing ability. 8 2000 by Elsevier Science Inc. Key words: boar reproduction, in vitro penetration, spermatozoa, semen analysis Acknowledgments W e acknowledge with gratitude the assistance with statistical analysis provided by Dr. A. Romar, and Dr. J.L. Alabart for critical reading of the manuscript. “Correspondence and reprint requests to Dr. J. Gadea, Departamento de Biologia Animal (Fisiologia Animal), Facultad de Veterinaria, Universidad de Murcia. 30071. Murcia. Spain. Fax: 34-968-364147. e-mail: jgadear&?um.es Theriogenology 54:1343-1357, 2000 0093-691 WOO/$-see front matter 0 2000 Elsevier Science Inc. PII: SOO93-691 X(00)00458-1