‘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 in population. An immediate subject of study was the chronological analysis of mortality in piglets from the breeding group of mini-pigs of ICG SB RAS (Institute of Cytology and Genetics Siberian Branch of Russian Academy of Sciences) for the period from 2013 through 2019. The results revealed increased number of dead piglets in the early postnatal period (first five days after farrowing) over this time period. This observation was confirmed by a statistically significant correlation coefficient between the year of birth and the number of animals that died during the first five days of life. Mortality in the period from the 6th day to weaning, on the contrary, decreased to probable accidental death which was non-related to genetic causes. Observed redistribution of mortality may be associated with increased general homozygosity in population and, in part, with the optimization of the excessive for mini-pigs multiple fertility. It is possible that the consequence of the second cause is an increase in mortality and a decrease in multiple 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 homozygosity to a level ensuring maximum survival of piglets on the 6th day after birth. Results of regression analysis showed that the mortality of piglets in 2018 reached its maximum level and in future a decrease to the optimum level which is typical for domestic pigs is possible. In general, results of this study suggest that newborn piglets are represented by two types. The first type includes animals whose viability potential determined by recessive lethal ‘genetic load’ is zero – they cannot live outside mother’s body. The second type is represented by animals with a genetic viability potential equal to one –they can die only from accidental death.