Functional characteristics of bovine spermatozoa in relation to the body condition score of bulls

Abstract

This study was aimed at examining possible impact of the body condition of breeding bulls on the motility and viability of the sperm following freezing-thawing. The breeding bulls (n = 16) of Holstein and Czech Fleckvieh breeds were classified to the body condition score (BCS) grade according to a five-point scale with an accuracy of 0.25 points. The sperm samples of the bulls estimated as BCS grades 2, 3 or 4 were frozen in a programmable freezing device and stored in a liquid nitrogen for approximately one year. Following thawing the motility parameters (total motility – TM; progressive movement – PM) were analysed using the CASA Sperm VisionTM system at the intervals of 0, 0.5 or 2 h post-thaw. Viability parameters of sperm - plasma membrane integrity (peanut agglutinin, PNA-FITC), apoptotic rate (Yo-Pro-1) and dead/necrotic cell (propidium iodide /DAPI) rates were analysed at the same day using fluorescent microscope. Only minor non-significant difference was observed between BCS2 and BCS3 bull sperm in all studied parameters. However, significant differences in the sperm parameters were noted between bulls with BCS2 and BCS4. In particular, the BCS4 bulls showed significantly lower (p ˂ 0.5) TM and PM than the BCS2 bulls. Moreover, significantly higher proportion (p ˂ 0.5) of sperm with damaged plasma membrane and dead/necrotic sperm was revealed in the BCS4 bulls compared to the bulls of BCS2. These observations indicate that higher score of the body condition may negatively affect the quality of bull ejaculates.