Perinatal losses in outdoor pig breeding. A survey of factors influencing piglet mortality

Outdoor keeping of breeding sows is rapidly developing for technico-economic reasons (chiefly limited investment), as well as to provide a more 'natural' environment, thus supposed to improve the welfare of animals when compared with indoor intensive systems. However, the piglet production has been cited as impaired, due to a higher early mortality. The yearly survey of the technical results of the French national herd shows that the piglet losses of outdoor sows are significantly higher than when compared with the national records for indoor herds (21.1% vs 17.4%; 76 578 and 867 719 litters respectively, for 1994, P < 0.001). This difference was consistent over the last few years. Mortality decreases from the first to the second litter and increases later on, and is higher during the late autumn-early winter period, but does not depend on the level of reproductive performance. The high loss outdoor herds are characterised by the different aspects of stockman intervention around parturition. The percentage of losses increases from 18.2% to 21.2% when parturition is watched over. Among the environment characteristics, a good quality of the pasture (well established grass cover) in the paddock characterises the low loss group. The percentage of piglet loss is negatively correlated with the amount of straw available in the hut (R = -0.355, P < 0.01).