Expression of amino acid and sugar transporters, aminopeptidase, and the di- and tri-peptide transporter PepT1; differences between modern fast growing broilers and broilers not selected for rapid growth.

Within the last 60 yr genetics of broilers have changed to produce rapid growing birds that achieve market weight in 6 wk or less. To investigate the differences in factors that play a role in nutrient processing and uptake between modern fast growing (Ross) and slow growing broilers not selected for growth (ACRBC), a study was carried comparing the expression of 13 genes that encode amino acid transporters (ASCT1, ATBo,+, BoAT, bo, +AT, CAT1, CAT2, EAAT3, γ+LAT1, and LAT1) and sugar transporters (GLUT2 and GLUT5), as well as aminopeptidase (APN) and the di- and tri-peptide transporter PepT1. The growth rate of Ross birds was approximately 4 times greater than that of ACRBCs, and the feed conversion ratio (FCR) was greater in ACRBCs at all-time points measured. Gene expression in the duodenum, jejunum, and ileum was measured at 1, 3, 5, 10, and 14 d post hatch (PH). The expression of genes that encode proteins (particularly ASCT1, ATBo, +, and BoAT) located at the brush border of the gut epithelium was generally higher in ACRBCs especially at earlier time points. The expression of genes that encode proteins located at the basolateral surface of the gut epithelium was less affected. The expression of GLUT2 and GLUT5 was significantly decreased in ACRBCs at most time points and gut segments. Based on the present data we conclude that expression of brush border and sugar transporters in the small intestine can be correlated with growth. Presented increases the identification of the factors that influence growth and will assist future studies of the function of these molecules.