‘GENETIC LOAD’ and changes in the chronology of early mortality in mini-pigs of ICG SB RAS

This paper describes the study of the common factors of mortality of suckling piglets.It is assumed that this parameter is influenced by recessive lethal factors of the genetic load inpopulation. An immediate subject of study was the chronological analysis of mortality in pigletsfrom the breeding group of mini-pigs of ICG SB RAS (Institute of Cytology and GeneticsSiberian Branch of Russian Academy of Sciences) for the period from 2013 through 2019. Theresults revealed increased number of dead piglets in the early postnatal period (first five daysafter farrowing) over this time period. This observation was confirmed by a statisticallysignificant correlation coefficient between the year of birth and the number of animals that diedduring the first five days of life. Mortality in the period from the 6th day to weaning, on thecontrary, decreased to probable accidental death which was non-related to genetic causes.Observed redistribution of mortality may be associated with increased general homozygosity inpopulation and, in part, with the optimization of the excessive for mini-pigs multiple fertility. Itis possible that the consequence of the second cause is an increase in mortality and a decrease inmultiple pregnancy. It is assumed that in the breeding group of mini-pigs of the ICG SB RAS,there is the process of eliminating excessive lethal ‘genetic load’ and optimizing homozygosityto a level ensuring maximum survival of piglets on the 6th day after birth. Results of regressionanalysis showed that the mortality of piglets in 2018 reached its maximum level and in future adecrease to the optimum level which is typical for domestic pigs is possible. In general, resultsof this study suggest that newborn piglets are represented by two types. The first type includesanimals whose viability potential determined by recessive lethal ‘genetic load’ is zero – theycannot live outside mother’s body. The second type is represented by animals with a geneticviability potential equal to one –they can die only from accidental death.