Abstract
Pig breeding is a crucial perspective of the livestock field, advancing improvement in genetics and higher animal production. In recent years, genomic selection has developed as the method of choice when it comes to the breeding of pigs. It is, therefore, a desire to use as young boars as possible in the breeding program. The sperm production relies on a mature spermatogenesis process, including a histone-to-protamine exchange to tightly pack the DNA. The aim of this study was to evaluate whether sperm cells from young boars differ in protamination level compared to spermatozoa from more mature boars. Semen samples were collected from the same Duroc boar at 7 months, 8.5 months, and 10 months to degree as the boar matured. This thesis explored the relationship between sperm quality and sexual development in Duroc boars by evaluating protamine deficiency, chromatin integrity, and sperm viability at three different ages. Flow cytometry techniques were optimized and applied, using Chromomycin A3 (CMA3) to assess protamine deficiency in Duroc boars. Additionally, sperm viability was evaluated using flow cytometry, and the Sperm Chromatin Structure Assay (SCSA) was used to analyze DNA fragmentation across three age groups. The replacement of histones with protamines begins early and occurs at a relatively stable rate. The CMA3 levels in sperm from young boars were slightly, yet significantly, lower than those in the two older age groups. A slight decline in sperm DNA Fragmentation Index (% DFI) was observed as the boars matured. However, this might not be of biological significance, since % DFI remained consistently below 1.1% across all age groups, indicating little influence on DNA integrity with advancing age in boars. This result indicates that younger boars can be a possible option for speeding up breeding cycles in livestock production without compromising protamine levels. It would be interesting to follow up on these results on a larger cohort of animals and with further research on different boar breeds.