Recent advances in sow nutrition

Sows produce a larger number of fetuses than before and these fetuses possess genetic potentials to grow faster than before. Recent comparison shows that a porcine fetus is 40% heavier than 40 years ago. Thus the nutritional management of sows has been updated to reflect these genetic changes. Our recent study quantified nutritional needs 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 (d 70 to farrowing) significantly greater than those needs during early gestation (until d 70). Considering these increases, daily requirement of true ileal digestible Lys for a primiparous sows increases from 7 g (until d 70) to 15 g (d 70 to farrowing). Required qualities of proteins (i. e., amino acid ratios) also change with an advance of pregnancy as maternal, fetal, and mammary tissues have their unique amino acid compositions. Thus, if the feed does not provide sufficient amounts and qualities of proteins, sows can be under a severe catabolic status during late gestation, especially during late gestation. Sows under a conventional feeding program had increased litter weight variations at farrowing (19%) compared with early gestation (3.0%). Our recent study also shows that sows under a conventional feeding program have a dramatic increase in a systemic oxidative stress during late gestation compared with early gestation when measured by plasma a-tocopherol (56% decrease), plasma retinol (57% decrease), and DNA damage in white blood cells (125% increase) which were sustained until the early lactation period. Increased oxidative damages in sows negatively affect the growth and health of fetuses as well as postpartum growth. Sow feeding during late gestation should reflect the changed needs for amino acids and antioxidants. Phase feeding or top dressing could be a practical solution to provide sufficient nutrients during late gestation.