Sow body composition and its associations with reproductive and litter growth performance of the primiparous sow

The complex of desirable maternal traits includes litter size, mothering ability and milk production, combined with aspects of piglet viability or survival and sow rebreeding performance. There are two major contradictory elements within this trait complex. Firstly, larger litters will be, on average, lighter at birth, and result in an extended duration of farrowing. These characteristics may affect piglet viability and access to colostrum, along with sow recovery and health after farrowing. Piglets from these litters are therefore more vulnerable to environmental stressors that can result in piglet death. Secondly, the sow’s ability to rear her litter must not compromise her own ability to rebreed for the next parity. So, increasing milk production per se to improve litter growth performance may be counterproductive if sow longevity is reduced by failure to rebreed. These areas of antagonism are likely strongest for primiparous sows, which balance their own growth and development against reproductive demands. This is generally illustrated by higher levels of piglet mortality and sow losses, and slower piglet growth, relative to litters and sows from later parities. Clearly a balance is required in performance attributes for phenotypic outcomes of both the sow and her offspring, and this may be particularly difficult to achieve in the first parity.