Correlation of CASA velocity and linearity parameters with sperm mobility phenotype in turkeys.

Since all domestic turkeys are produced through artificial insemination, a measurable sperm characteristic that would be predictive of fertility would allow for the culling of poor males, resulting in improved reproductive efficiency. The sperm mobility test (SMT), which quantifies sperm penetration into an Accudenz solution, has been shown to correlate highly with fertilization potential of individual turkeys. Since this sire-selection test is based on the differences in sperm mobility between whole ejaculates from individual males, the objective of this study was to determine whether specific sperm velocity parameters would correlate with the SMT and to determine whether these characteristics could account for phenotypic differences in sperm mobility observed between males. The SMT was used to rank males within a flock (n = 110) in triplicate and to classify them into high, average, and low sperm mobility phenotypes on the basis of the sperm mobility index. Several sperm velocity parameters were evaluated for each male by a computer-aided sperm analysis (CASA) system, the Hobson Sperm Tracker. The types of measurements taken of 200 sperm tracks/ejaculate included the following: curvilinear velocity (VCL), average path velocity (VAP), straight-line velocity (VSL), linearity (LIN), beat-cross frequency (BCF), and mean angular displacement (MAD). Significant positive correlations were found between VSL, LIN, BCF, and sperm mobility, and a significant negative correlation was seen between MAD and sperm mobility. Subpopulations of sperm that had penetrated the Accudenz solution were isolated from each mobility phenotype and were analyzed by CASA, and significant correlations were again observed between VSL, LIN, BCF, and sperm mobility. We conclude that sperm velocity and linearity contribute to overall sperm mobility phenotype and are important characteristics of turkey sperm function. Key words: Motility, computer, spermatozoa.