Effects of in ovo injection of carbohydrate solution on small intestine development in domestic pigeons (Columba livia)

The objective of this study was to test the hypothesis that in ovo injection of carbohydrates into pigeon (Columba livia) amnion may improve the small intestine development. At d 14.5 of incubation, 80 fertile eggs were injected with 200 mu L of carbohydrate solution, and 80 control eggs were not injected. The carbohydrate solution (wt/vol) contained 2.5% maltose + 2.5% sucrose, all dissolved in 0.75% saline. Twelve eggs from each treatment were randomly sampled at d 16 of incubation and the day of hatch, embryos or young pigeons were euthanized, and the jejunum samples were collected. Jejunal villus surface area, activity of the brush border enzymes, sucrase, maltase, aminopeptidase-N, and alkaline phosphatase, and mRNA expression of the digestion-absorption related genes oligopeptide transporter 1, sodium glucose transporter 1, glucose transporter 2, aminopeptidase-N, and sucrase-isomaltase were examined. Results showed that in ovo injection of carbohydrate solution caused a villus surface area increase of 38% on d 16 of incubation and 23% on day of hatch relative to controls (P < 0.05). The in ovo injected pigeons exhibited greater (P < 0.05) activities of jejunal sucrase, maltase, and alkaline phosphatase from d 16 of incubation to day of hatch compared with the controls. At day of hatch, aminopeptidase-N activity in embryos injected in ovo was approximately 27% greater (P < 0.05) than control embryos. Enhanced expressions of the jejunal sodium glucose transporter 1, glucose transporter 2, and aminopeptidase-N mRNA were found at d 16 of incubation in embryos that received carbohydrate solution into the amniotic fluid in comparison with the control group (P < 0.05). These results indicate that the in ovo injected pigeon may hatch with more mature enterocytes and greater intestinal digestive and absorptive capacity than the conventional hatchling. Therefore, the in ovo injected pigeons may become more precocial at hatch and easier to hand-rear during the immediate posthatch period.