Amino acid composition of the fetal pig

Amino acid composition and accretion were determined in fetal pigs obtained from gilts by hysterectomy at d 40-114 of gestation. The whole homogenate of the fetal pig was used for analysis of dry matter, nitrogen and amino ac ids. Uterine uptake of amino acids was estimated at d 110-114 of gestation on the basis of uterine arteriovenous concentrations. Nitrogen and amino ac id accretion in fetal pigs increased more rapidly with gestation than non-n itrogen dry matter. Amino acid nitrogen represented 83-88% of total nitroge n, and arginine was the most abundant nitrogen carrier in fetal pigs at all gestational ages. Amino acid composition changed with gestation, with glyc ine and hydroxyproline increasing (P < 0.05) markedly and other amino acids (except ornithine and tryptophan) decreasing (P < 0.05) to a lesser extent . Amino acid concentrations in fetal pigs increased (P < 0.05) progressivel y from d 60 to 114 of gestation. Uterine uptake of arginine and proline plu s hydroxyproline met requirements for fetal growth during late gestation on ly marginally, and uterine uptake of aspartate/asparagine and glutamate was only 9-29% of fetal accretion. In contrast, uterine uptake of citrulline a nd ornithine was 55- and 15-fold greater (P < 0.05) than fetal accretion, r espectively. On the basis of hydroxyproline content, collagen was estimated to represent similar to 7, 15, 25, 28 and 29% of total body protein at d 4 0, 60, 90, 110 and 114 of gestation, respectively. Amino acid composition o f the fetal pig is similar to that for the human fetus, indicating that the pig is an excellent model for studying amino acid nutrition and metabolism in the human preterm neonate and infant.