Effects of Incubation Temperature and Transportation Stress on Yolk Utilization, Small Intestine Development, and Post-Hatch Performance of High-Yield Broiler Chicks
Growth and performance parameters of broiler chicks depend on adequate development of the small intestine. Stressors such as elevated or decreased temperatures during incubation and post-hatch transportation may have an effect on the gastrointestinal development of the broiler chick. The objective of the first study was to investigate the effects of elevated embryonic incubation temperature (IT) on post-hatch relative nutrient transporter gene expression, integrity of the intestinal epithelium, organ development, and performance in Ross 308 broiler chickens. Nine hundred fertile eggs were incubated at different egg-shell temperatures during development. Body weights and performance parameters were measured at day of hatch (DOH), d 7, 14, 21, 30, and 42. Small intestine and residual yolk were collected at DOH, d 2, 4, 6, and 10 and weighed individually. The small intestine was evaluated for mucosal morphology measurements and relative nutrient transporter (SGLT1, GLUT2, GLUT5, EAAT3, and PepT1) gene expression. The objective of the second study was to evaluate the effects of embryonic incubation, simulating a multi-stage incubation system, and post-hatch transportation temperatures on post-hatch performance, yolk free body weights, relative nutrient transporter gene expression, yolk utilization, intestinal morphology, and organ development of broiler chickens. Cobb 500 eggs (n=5200) were incubated with egg-shell temperatures, which were combined depending on the early and late development incubation periods as found in multi-stage incubators: Low (L): 36.7°C, Standard (S): 37.5°C, and High (H): 39°C. After hatch, chicks were further separated into 2 transportation groups: control (C; 34°C), and heat-stressed (D; 40°C). The eight resulting experimental groups were: LS-C, SS-C, LH-C, SH-C, LS-D, SS-D, LH-D, and SH-D. Three and two way interactions (P<0.05) were observed and discussed in both studies for all the parameters analyzed. These studies present for the first time the effects of altered embryonic IT and stress during transportation of newly hatched chicks, on small intestine morphology, digestive organ development, and expression of nutrient transporters mRNA in high-yield broiler chicks. These results contribute to the understanding of mechanisms by which either low or high temperatures, as compared to standard recommendations, during incubation and transportation can affect embryonic development and subsequent performance of broiler chicks.