Effects of sow nutrition during gestation on within-litter birth weight variation: a review

The increasing demand for efficiency in pork production requires great specialization of all sectors involved in this activity. In this
context, the development of strategies that could reduce undesirable traits related with negative effects on piglet survival and
postnatal growth and development are essential for the pig industry. Currently, special attention is given to variation in birth
weight, as some evidences suggest an increased within-litter birth weight variation in modern sows. This variation has been
shown to be associated with preweaning mortality, variable weights at weaning and deteriorated growth performance, which
results in economic losses and lower efficiency. Therefore, understanding the factors that can influence the events that occur
during gestation and that have an impact on the fetal growth and development are important to achieve better efficiency and
also to develop strategies that can be used to achieve increased within-litter uniformity of piglet birth weight. This study
concludes that even at a given placental size, fetal growth may vary because of differences in placental vascularization and
efficiency. Feeding extra feed or energy during late gestation only marginally improves birth weight, and positive effects are
not consistent between different studies. The detrimental effects of protein restriction on fetal growth during early gestation may
be due to altered placental and endometrial angiogenesis and growth, which leads to a reduction in placental-fetal blood flow,
nutrient supply from mother to the fetuses and ultimately to fetal growth retardation. The number of studies that attempted to
influence within-litter birth weight variation by means of sow nutrition during gestation is limited. Therefore, more research
concerning sow nutrition during gestation associated with the provision of balanced diets to meet requirements of the sows
and fetuses are still required. This knowledge may subsequently provide starting points for the design of nutritional strategies
that can influence within-litter birth variation.

PCampos_2011_Effects of sow nutrition during gestation on within-litter birth