This study was conducted to investigate the gene expression of cationic and neutral amino acid (AA) transporters in the small intestine of chick embryos with different genetic backgrounds [Wenshi Yellow-Feathered chick (WYFC) and White Recessive Rock chick (WRRC)]. The study also investigated the correlation between the abundance of AA transporter mRNA and the AA content of fertilized eggs. Intestinal samples were collected on embryonic d 9, 12, 14, 17, and 19 and the day of hatch. The results showed that, before incubation, the AA content of WRRC eggs was lower (P < 0.05) than the AA content of WYFC eggs. In WYFC, the mRNA abundance of CAT-1 [solute carrier (SLC) family 7 member 1], CAT-4 (SLC family 7 member 4), rBAT (SLC family 3 member 1), y(+)LAT-1 (SLC family 7 member 7), y(+)LAT-2 (SLC family 7 member 6), LAT-4 (SLC family 43 member 2), and SNAT-2 (SLC family 38 member 2), as detected by real-time reverse transcriptase PCR, was greater (P < 0.05) than the mRNA abundance detected in the WRRC samples. The mRNA abundance of all measured AA transporters was affected (P < 0.05) by embryonic age. Sex had the largest effect (P < 0.05) on the mRNA expression of CAT-1, CAT-4, y(+)LAT-2, and LAT-4 in WYFC and on CAT-4 and B(0)AT-1 (SLC family 6 member 19) mRNA expression in WRRC. In WYFC, only CAT-1 mRNA expression was negatively correlated (r = -0.68 to -0.84, P < 0.05) with all AA content. However, few correlations were detected between AA content and the mRNA expression of multiple transporters in WRRC. These findings provide a comprehensive profile of the temporal and spatial mRNA expression of AA transporters in the small intestine of chick embryos. Few correlations were detected between the AA content of the eggs and mRNA expression of specific AA transporters in the small intestine.

The objective of this study was to investigate the effect of egg weight on the composition of the egg, the growth of the embryo, and the expression of amino acid transporter genes in the yolk sac membranes and small intestines of the domestic pigeon (Columba livia). A total of 240 fertilized eggs were collected and divided into two groups based on the weight of the eggs, light (LE) and heavy (HE). The composition of 20 eggs from each group was measured, and the remaining eggs were weighed and placed in an incubator. On embryonic days (E) 9, 11, 13, and 15 and day of hatch (DOH), 15 embryos/hatchlings from each group were measured for embryonic growth, and samples were collected. The HE had heavier yolk and albumen weights than the LE (P < 0.01). Compared with the LE, the HE had heavier yolk-free embryonic body and yolk sac weights from E13 to DOH (P < 0.05). Additionally, the HE had larger yolk sac membrane weights from E13 to E15 (P < 0.05) and had more residual yolk sac content on DOH than those of the LE (P < 0.01). The yolk absorption was greater for the HE than for the LE from E11 to E13 (P < 0.05). Furthermore, the abundance of CAT2 and PepT1 mRNA in the yolk sac membranes was greater in the HE than in the LE on E13 (P < 0.05). Compared with the LE, the gene expression of EAAT2 in the intestine on E13 was greater in the HE, whereas the expression of EAAT3 was lower in the HE (P < 0.05). Taken together, our results suggest that egg weight influenced the composition of the eggs, embryonic development, and expression of amino acid transporter genes in the yolk sac membranes and small intestines of pigeon embryos.