title: Identification of sperm morphometric subpopulations in two different portions of the boar ejaculate and its relation to postthaw quality.
abstract: A statistical approach using sequentially principal component analysis (PCA), clustering, and discriminant analyses was developed to identify sperm morphometric subpopulations in well-defined portions of the fresh boar ejaculate. Semen was obtained as 2 portions (the first 10 mL of the sperm-rich fraction and the rest of the ejaculate, respectively) and frozen using a conventional protocol. Before freezing, an aliquot was used for computer-assisted sperm morphometry analysis (ASMA). Postthaw quality was evaluated using computer-assisted sperm analysis (CASA), and an annexin-V/PI assay evaluated sperm membranes. The PCA revealed that 3 variables represented more than 78% of the cumulative variance in sperm subpopulations. The clustering and discriminant analyses, based on 5780 individual spermatozoa, revealed the existence of 4 sperm subpopulations. The relative percentage of these subpopulations varied between boar and ejaculate portions. Linear regression models based on measured morphometric characteristics could account for up to 36% of the percentage of intact sperm membranes postthaw. The ASMA protocol used in our study was useful to detect subtle morphometric differences between spermatozoa, and the combination of this analysis with a multivariate statistical procedure gave new information on the biological characteristics of boar ejaculates that is not given by conventional sperm analysis.
authors.affiliation: Section of Animal Reproduction and Obstetrics, Department of Herd Health and Medicine, Faculty of Veterinary Medicine, University of Extremadura, Cáceres, Spain. fjuanpvega@unex.es
authors.forename: Fernando J
authors.initials: FJ
authors.lastname: Peña
authors.forename: Fernando
authors.initials: F
authors.lastname: Saravia
authors.forename: Manuel
authors.initials: M
authors.lastname: García-Herreros
authors.forename: Ivan
authors.initials: I
authors.lastname: Núñez-martínez
authors.forename: Jose Antonio
authors.initials: JA
authors.lastname: Tapia
authors.forename: Anders
authors.initials: A
authors.lastname: Johannisson
authors.forename: Margaretha
authors.initials: M
authors.lastname: Wallgren
authors.forename: Heriberto
authors.initials: H
authors.lastname: Rodríguez-Martínez
mesh_terms: D000818:Animals; D015925:Cryopreservation / Q000379:methods / Q000662:veterinary*; D016002:Discriminant Analysis; D004542:Ejaculation; D008297:Male; D025341:Principal Component Analysis; D012662:Semen Preservation / Q000379:methods / Q000662:veterinary*; D013081:Sperm Motility; D013094:Spermatozoa / Q000145:classification* / Q000166:cytology*; D013552:Swine