Amino acid composition of fetus, placenta, and uterus in gilts throughout gestation1

An accurate understanding of the AA composition of the products of conception is needed to accurately model dietary AA needs of pregnant swine. To determine AA composition in fetal pigs, the placenta, and the uterus at various stages of gestation, samples from a total of 65 gilts slaughtered at assigned days of gestation (d 43, 58, 73, 91, 101, and 108) were used. The AA concentrations (g/kg each wet tissue) in the fetus, placenta, or uterus increased as gestation progressed, with major increases occurring from d 73 to 108 of gestation (P < 0.05). For fetus, AA content on a DM basis (%) and AA contribution to total fetal AA (g/100 g total AA of fetal tissue) generally decreased as gestation progressed (P < 0.05) except for Arg and Ala, which increased from d 73 of gestation, and for Gly and Pro, which increased progressively (P < 0.05) from d 43. Placental AA content on a DM basis increased up to d 91 or 101 of gestation (P < 0.05) and then slightly decreased on d 108 of gestation except for His, Cys, and Met + Cys. Amino acid contribution to total placental AA decreased for all AA as gestation progressed (P < 0.05), except for Arg, Ala, Gly, and Pro, which increased from d 58 of gestation. Essential AA content in the uterus on a DM basis had no major changes during gestation, whereas nonessential AA content decreased (P < 0.05) as gestation progressed, except for Asp. For AA contribution to total uterine AA, some essential AA (Ile, Leu, Lys, Met, Trp, and Val; P < 0.06) and Asp (P < 0.01) contributions increased with increasing gestational ages, whereas Arg (P = 0.08), Cys, Gly, and Pro (P < 0.05) contributions decreased as gestation progressed. Differences in AA contribution to total AA within each tissue varied among the fetus, placenta, and uterus by type of AA. These results demonstrate that AA compositions of fetal pigs, placenta, and uterus are changed differentially as gestation progresses; in particular, Arg, Ala, Gly, and Pro compositions in fetus and placenta increased progressively. These compositional data for each reproductive tissue and fetus will help to model AA requirements in gestation.