Bull sperm head morphometry related to abnormal chromatin structure and fertility

Abstract

This study investigated the relationship between morphologically abnormal sperm, sperm chromatin structure, and fertility. Semen samples were obtained from 13 bulls. The sperm chromatin structure assay (SCSA), a sensitive measure of denaturability of sperm nuclear DNA in situ following acid treatment, was performed on each sample to quantitate abnormal chromatin structure. Feulgenstained sperm head morphology was measured by computerized image analysis (ONCOR-Image): Sixteen parameters were measured for each of 200 nuclei per sample. Fertility estimates were available for nine of the bulls. The SCSA variable SD alpha t was correlated with fertility ranking (r = 0.617, P < 0.01). No correlations were seen between means of the imaging variables and SCSA variables % COMP alpha t or SD alpha t. Significant correlations (P < 0.05) were seen between SD alpha t and the variation of imaging variables eccentricity, width, and light blobs. Significant correlations (P < 0.05) were seen between % COMP alpha t and the variation of imaging variables area, perimeter, p2a, bending energy, nmac, sphericity, eccentricity, length, and width. A regression model for fertility rankings incorporating the standard deviation of the imaging variables area, bending energy, nmac, eccentricity, condensity, light blobs, and dark blobs was highly significant (r2 = 0.999, P < 0.05). These results indicate that variation of morphometry measurements is likely a sensitive biomarker related to fertility potential and abnormal chromatin structure.