The effect of the in ovo injections of dextrin and L-carnitine in conditions of thermal stress during the incubation period on the embryonic development and growth of broiler chickens

The embryonic thermal stress due to the overheating is a common problem of the incubation of broiler eggs and hence the search for the methods of metabolic corrections of the related shifts in the embryonic development can be practically actual task. The aim of the research was to study the effect of the in ovo injections of heat stressed chicken embryos with the combination of dextrin (as glucose source) and L-carnitine on the efficiency of incubation and early postnatal growth rate. The study was performed in 2020 on incubated eggs, embryos and chicken of Cobb-500 final hybrid cross. Three groups of eggs (n = 62) were formed for each temperature regime of incubation: without injections, physiological saline injection, injections with the solutions of dextrin (10%) and L-carnitine (0.6%). The eggs were injected with physiological saline, the solutions of dextrin and L-carnitine at the 17th day of incubation. Then the incubation was carried out in hatchers at normal temperature (37.2 °С) and increased temperature (38.5–39.0 °С). The increased temperature during hatching period on average among the groups decreased the hatchability of eggs by 6.1 % and relative weight of chicken by 0.96 %. The injection in ovo with the mixture of dextrin and L-carnitine 1.6–3.2 % increased the hatchability of eggs incubated at increased and normal temperature, respectively. The live weight of day-old chicks injected in ovo with the solution of dextrin and L-carnitine at normal temperature was significantly higher by 1.3–2.3 % (p <0.05) as compared with control groups. Neonatal growth rate was higher in chicken injected in embryonic period with dextrin and L-carnitine both at normal and increased temperature – live weight of 7-day chicken of the experimental groups was 5.9 and 5.1 % higher (p <0.05) compared with the control groups of the same temperature regime. In chicken incubated at increased temperature the differences remained to 35 days of age and were 5.7 % (р <0.05). Biochemical variations were noted in blood parameters of embryos of the control and experimental groups that proved the absorption of exogene nutrients and biologically active substances by the embryo. Thus, in blood plasma of 17-day embryos injected in ovo with the solution of dextrin and L-carnitine the concentrations of glucose significantly increased by 1.6-1.7 % (p< 0.001) and triglycerides by 46.2 % (p <0.05). So, by injecting the incubated eggs during hatching period with the solution of dextrin and L-carnitine, the neonatal growth rate of chicken raised at normal and increased temperature and during heat stress as well. No significant effect of the injection on the hatchability of eggs in conditions of thermal stress in the hatching period was found.