Sex-sorting of sperm cells is a technology that is growing globally for the use in the breeding of cattle. Sorting of X- and Y-Chromosome bearing spermatozoa is done by flowcytometry before cryopreservation and it is important to be able to recognize possible damages caused by the methods, as well as having analytical tools to illustrate possible differences in fertility potential and bull to bull differences. The main objective for this thesis was to establish a motility stress test and a new analytical tool for measurement of lipid peroxidation as an indicator for oxidative stress, specifically designed for Norwegian Red sexed spermatozoa.
Various sperm quality parameters were analyzed for sex-sorted Norwegian Red spermatozoa, including motility by Computer Assisted Sperm Analyzer, ATP level and lipid peroxidation by plate reader and viability and acrosome integrity by flowcytometry after different time of incubation. The motility stress test showed a significant decline from pre and post incubation in total motility and progressive motility (P<0.05), therefore ATP level, MDA concentration, viability, and acrosome integrity were examined before and after incubation for 120 minutes at physiological temperature, in an effort to characterize possible causes for the decline in motility. The ATP measurement found a significant decline between pre and post incubation (P<0.05), likewise as the motility stress test, meaning that the loss of motility could be caused by low amounts of energy. Analysis of lipid peroxidation using the biomarker MDA showed that the loss of motility was not caused by lipid peroxidation. Thus, in further studies other types of oxidative stress biomarkers could be better suited for examining the relationship between motility and oxidative stress in sexed spermatozoa. However, the assessment of acrosome intact live spermatozoa post incubation showed that about half the sperm cells were still viable, meaning that some immotile spermatozoa may still have the ability to become motile again. This might prove to be a vital new parameter in terms of fertility prediction in sexed Norwegian Red spermatozoa for AI centers.
After the motility stress test and the new analytical tool for lipid peroxidation was established, sex-sorted spermatozoa from six Norwegian Red bulls with known field fertility were examined for total motility, progressive motility, velocity parameters (VCL and VAP) and lipid peroxidation (MDA). There were found some differences between high and low fertility groups, however further research must be conducted with an increase in the number of bulls to determine whether association between fertility and the quality parameters are significant