The aim of this study was to determine by SDS PAGE the protein profile of the seminal plasma of Romosinuano (ROMO) and Costeño con Cuernos (CCC) bulls and their relationship with sperm quality parameters in fresh and thawed semen. Three ejaculates per bull were collected by electro-ejaculate from 10 ROMO and 10 CCC sires. Viability (VF), mass motility (MMF), individual rapid progressive motility (MIRPF) and sperm concentration (CE) were determined in fresh semen. Seminal plasma (PS) was obtained by double centrifugation. Individual motility of rapid progressives (MIRPPC), progressivity (PRPC), rapid progressives (RPPC) and medium progressive (MPPC) were determined in thawed semen, in both cases using the CASA computerized analysis system. Additionally, viability (VPC) and membrane integrity were determined by the hypoosmotic test. Proteins were separated by polyacrylamide gel electropho...