2. Material and methods
2.1. Animals and environment
Data were recorded from January to December 2004 in a nucleus herd of the ‘Hülsenberger Zuchtschweine’ breeding company in Austria. Information of 386 Landrace sows with 438 pure-bred litters was available. Sows were housed in diagonally ordered farrowing pens of homogeneous type with dimension of 2.74 m × 1.75 m during lactation (Fig. 1). Crate dimensions were individually adjusted to the size of each sow. No nesting material was provided for the sows. Twenty sows were penned per farrowing compartment, ordered by the calculated farrowing date. In the farrowing pen, underfloor heating and heat lamps were provided. The piglet nest area was located laterally beside the sow. The sows were managed in a 1-week rhythm with a 21-day lactation period. They were fed once per day, and from the second day post partum twice per day. During the whole study time, no medication was administered.