“…If the carrier sows for the mutant allele are more prone to stress, it may be a prerequisite for reducing their reproductive ability. Regarding the susceptibility of certain breeds of pigs, Pietren, Polish-Chinese pigs, Landrace, Hampshire and Yorkshire are considered to be quite prone to stress while Chester White, Duroc, Large White and Berkshire are considered stress-resistant (Ivanov & Guk, 2019;Sipahelut et al, 2019;Rodríguez et al, 2020). In our studies, only 6.4% of animals carrying the mutant allele of the RYR1 gene were detected, while homozygous animals with the mutant allele of this gene were not detected at all.…”