Genetics of sow performance in piglet production

Abstract: The aim of this thesis was to provide knowledge about the genetic relationships concerning sow performance in piglet production. During the last decades, selection in dam lines has focused on increasing litter size and piglet growth. Consequently, the demand on the sow to provide her piglets with enough milk increases. At the same time, breeding for animals with less fat limits the sow’s possibility to store body reserves to be used during lactation. Poor body condition is related to reproduction problems and welfare problems such as shoulder ulcers. In this thesis, piglet growth, feed intake, sow body condition, shoulder ulcers and a number of reproduction traits were studied. Breeding for increased mean piglet weight, as a trait of the sow, will increase weight heterogeneity in the litter. Sows with a genetic ability for high feed intake raise heavy litters. A heavy litter is genetically related to poor body condition of the sow at weaning. Shoulder ulcers in lactating sows is a heritable trait. Sows producing heavier piglets and sows with poor body condition have an increased risk of developing shoulder ulcers. It is important to take into account shoulder ulcers in breeding programs to improve both sow welfare and profitability. Selection for high piglet growth may deteriorate the sow’s condition at weaning, which will affect the following reproduction cycle in a negative way. Selection for litter growth or piglet growth (as maternal traits) in 1st litter may prolong the interval from weaning to mating and decrease litter size in 2nd litter. Maintaining a good body condition is central for sow performance in piglet production and sow body condition should be included in the genetic evaluation to ensure sufficient reproduction and welfare of the sows. Even if selection for improved sow performance in piglet production is important, further development of management and feeding routines is necessary to provide the environment needed for the sows to be able to express their genetic potential.