Nearly 80% of the preweaning mortality occurs during the perinatal period, i.e. during farrowing and the first 3 days after birth. Most of the perinatal mortality is due to non-infectious causes and many of these may result from problems of adaptation and development. A main factor affecting perinatal mortality and morbidity is the uterine capacity and mothering ability of the sow, which is influenced by genetics. The larger the litter the greater the possibility of the occurrence of placental insufficiency, and thus the greater the risk of the fetus being exposed to repeated incidents of hypoxia. This hypoxia may lead to hormonal changes that ultimately disturb the development of the various organs, especially the liver and adrenals. Thus some of the pigs in a litter may lack the extra strength to withstand the stress of being born, or may be handicapped in some way. Mothering ability partly depends on the early experiences of the sow and how she adapts to the existing housing, husbandry and management routines. The significance of housing and management procedures on the occurrence of perinatal mortality is discussed, and the influence of nutrition mentioned. Reducing the perinatal mortality not only involves breeding programs, but also improvement in sow living conditions. In addition, proper care at farrowing, especially with respect to the special needs of the newborn pig, can play a major role in decreasing the perinatal losses.
