Abstract
Fetal death in the last few days of pregnancy or neonatal death were observed in rats fed a 10% soy protein isolate (SPI) diet throughout pregnancy. Among pregnant rats fed a 10% SPI diet supplemented with 0.3% L-methionine or 0.15% L-threonine, 0.2% L-valine and 0.3% L-methionine or fed a SPI diet at a level of 20%, 25%, 35% and 50%, only the 50% SPI diet group showed improved pregnancy and delivery. In the last two or three days of pregnancy, the food intake of the 10% SPI diet group was very small and the biological value was significantly lower after day 15-16 of pregnancy than that in the 10% whole egg protein (WEP) diet group. The free amino acid concentrations in plasma of the 10% WEP and 50% SPI diet groups at day 21 of pregnancy were lower than those at day 7 or 14, while that of the 10% SPI diet group was higher at day 21 than that at day 7 or 14. Pregnant rats fed the 10% SPI diet seemed to have difficulty in utilizing free amino acids in the last one week of pregnancy. It was considered that in the last week of pregnancy, the amino acid composition of the 10% SPI diet was not sufficient for improvement of maternal metabolism and fetal growth, whereas sufficient improvement was observed with the 50% SPI diet.
