Material and methods
The research material consisted of 309 primiparous and 625 multiparous sows
(PLW × PL). Sows were chosen from different parities without analysing whole
live production. Animals were housed in a state-owned industrial piggery (i.e. PPH
Ferma-Pol Zalesie), located in the Opole region in the period January 2006 to July
2011