Swine nutritionists are investigating whether nutritional factors impacting prenatal growth and development can influence postnatal pig performance.

If the fetus is stressed during development, the pig may be programmed for a lifetime of unfavorable consequences, explains Lee Johnston, swine nutrition and management professor at the University of Minnesota (UM) West Central Research and Outreach Center in Morris, MN.

“When programming occurs during fetal development, it is called fetal imprinting. Many researchers working with different species have suggested that reduced or altered fetal growth compromises postnatal growth and performance,” Johnston says. “The central question becomes, how can we improve nutrient supply to developing fetuses to decrease incidence of low birth weight pigs? Specifically, we would like to increase nutrient supply in the uterus to the ‘disadvantaged’ piglets that will appear as runts at parturition.”

Johnston and UM colleagues Jerry Shurson and Mark Whitney have been conducting extensive reviews of previous research findings relating to nutritional factors that might be able to help improve the fetal environment.

Some research has looked at increasing overall nutrient intake in order to lower the number of low birth weight pigs. However, overall, researchers have found providing more nutrients than recommended does not seem to have a lasting effect on the pigs that are born. Johnston says a more targeted approach appears to be necessary.

Since the placenta is the link between maternal nutrient supply and the developing fetus, some researchers have focused on methods to improve placental size and function. Increasing blood flow through the placenta and improving placental function allows increased nutrient supply to fetuses and increased fetal growth. Polyamines, such as putrescine, spermidine and spermine, in addition to nitric oxide, are important compounds in the development of blood vessels in the placenta. The amino acid arginine can be an important determinate of polyamine supply.

Research conducted in 2007 by Ronaldo Mateo, Texas Tech University, suggested high levels of dietary arginine fed to gilts from Day 30 of gestation through birth of the piglets had no effect on total number of pigs born per litter, but did increase the number born alive by two.

In a subsequent study, similar levels of arginine supplementation had no effect on any litter characteristics at birth. Johnston says the results of Mateo's work point to a need for more research into the role arginine may play in improving the fetal environment.

“More targeted feeding to improve placental function and efficient fetal nutrient transfer may help fetal growth,” he says. “However, there are no proven, practical ways to improve placental function. Supplementing diets with polyamines, such as putrescine, spermidine or spermine, or their precursor, arginine, may be a practical solution. There is some scientific evidence suggesting sows may have improved reproductive performance if their diets are supplemented with high levels of arginine.”

It's too early to tell if nutritional imprinting strategies would be practical in a day-to-day pork production operation, Johnston says.