Mitochondrial haplotypes: the effect of reproductive disorders in pigs

The study presents the results of a literature review and original research on the influence of mitochondrial DNA (mtDNA) haplotypes on oocyte quality and genetic diversity in pigs of different breeds, based on the analysis of mtDNA polymorphism. mtDNA pathologies in oocytes arise from various factors such as aging, metabolic disorders, obesity, and reduced genetic diversity. A direct effect of mtDNA haplotypes on pig reproduction has been established, which contributes to a better understanding and diagnosis of pathologies underlying oocyte health deterioration. Three groups of mtDNA haplotypes were identified in Russian pig breeds, indicating limited genetic diversity. It was shown that sows with haplotypes D and E exhibit earlier oocyte maturation compared with offspring predominated by haplotype A, which demonstrated the lowest reproductive efficiency. According to the results, haplotypes D and E are more stable in pig populations, as litters from their carriers averaged 12 or more piglets born. The obtained data demonstrate a correlation between genetic variability in natural mitochondrial haplotypes and the number of piglets per litter. Analysis of mtDNA mutations in sows is an important tool for studying the influence of haplotypes on oocyte maturation and for predicting embryo survival in the maternal organism. Thus, improving oocyte quality through mitochondrial enhancement appears to be a novel approach to managing reproductive outcomes and determining sow productivity. It can be assumed that markers of mitochondrial dysfunction in high-quality oocytes may serve as prognostic indicators in assisted reproductive technology protocols.