Sows produce alarger number of fetuses than before and these fetuses possess genetic potentialsto grow faster than before. Recent comparison shows that a porcine fetus is40% heavier than 40 years ago. Thus the nutritional management of sows has beenupdated to reflect these genetic changes. Our recent study quantified nutritionalneeds for sows to support the growth of fetuses and mammary glands during gestation.Amino acid needs for fetal growth and mammary growth during late gestation (d70 to farrowing) significantly greater than those needs during early gestation(until d 70). Considering these increases, daily requirement of true ileal digestibleLys for a primiparous sows increases from 7 g (until d 70) to 15 g (d 70 tofarrowing). Required qualities of proteins (i.e., amino acid ratios) also changewith an advance of pregnancy as maternal, fetal, and mammary tissues have theirunique amino acid compositions. Thus, if the feed does not provide sufficientamounts and qualities of proteins, sows can be under a severe catabolic statusduring late gestation, especially during late gestation. Sows under a conventionalfeeding program had increased litter weight variations at farrowing (19%) comparedwith early gestation (3.0%). Our recent study also shows that sows under a conventionalfeeding program have a dramatic increase in a systemic oxidative stress duringlate gestation compared with early gestation when measured by plasma α-tocopherol(56% decrease), plasma retinol (57% decrease), and DNA damage in white bloodcells (125% increase) which were sustained until the early lactation period.Increased oxidative damages in sows negatively affect the growth and healthof fetuses as well as postpartum growth. Sow feeding during late gestation shouldreflect the changed needs for amino acids and antioxidants. Phase feeding ortop dressing could be a practical solution to provide sufficient nutrients duringlate gestation.
