Effect of egg weight on composition, embryonic growth, and expression of amino acid transporter genes in yolk sac membranes and small intestines of the domestic pigeon (Columba livia)

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.