Genetic and non-genetic factors influencing piglet stillbirth risk

Piglet mortality is a major challenge in organic production and in recent years there has been increasing public concern about the level of animal losses before weaning. The main objective of this study was the analysis of the relative role of genetic and non-genetic risk factors for stillbirth in piglets of the world's widely represented breeds. A total of 2,817 litter records of productive parent sows were collected between 2010 and 2013. The following traits were estimated for each litter: the number of stillborn piglets per litter and the stillbirth rate, defined as the number of stillborn piglets divided by the total number of piglets born per litter. In addition, the proportion of litters with at least one stillborn piglet was determined also. The proportion of litters with at least one stillborn piglet for the study sample was 59.2%, indicating that the majority of sows exhibited the occurrence of at least one stillbirth. The mean number of stillborn piglets ranged from 0 to 15 head, with a mean of 1.40 ± 0.03 head, and the range of stillbirth rates per litter was 0 to 100%, with a mean of 12.91 ± 0.28%. The breed of the boar had a highly statistically significant impact on all piglet loss traits at birth employed in the analyses. The mean piglet losses estimates for the piglets born in the Large White boar litters were all found to be lower than those for the piglets born in the Duroc and Landrace boar litters. The year of farrowing also significantly influenced the observed traits, particularly for the number of stillborn piglets per litter and the stillbirth rate. The highest values were observed for litters born in February-March, while farrowing in May exhibited the lowest piglet losses at birth. Furthermore, the sows with the shortest gestation length (110 days) always had at least one stillborn piglet per litter. A significant increase in piglet mortality at birth was associated with an increase in total litter size, both at the level of individual sows and piglets per litter. The optimal average piglet birth weight value, at which piglet losses at birth were lowest, was 1700 g or more. Conversely, piglets with lower average piglet birth weight values exhibited a higher probability of dying at birth or immediately thereafter. As the variability in live birth weight of newborn piglets increased, there was a notable rise in the frequency of litters with at least one stillborn piglet. The lowest proportion of litters with at least one stillborn piglet values were observed in litters in which all newborn piglets had the same body weight at birth. The potential for research on stillbirth includes the analysis of its impact on the average daily growth rates and survival of piglets until weaning, as well as its effect on the development of performance, meat and carcass traits of fattening pigs.