Wider Angle Egg Turning during Incubation Enhances Yolk Utilization and Promotes Goose Embryo Development

Notch mediates the glycolytic switch via PI3K/Akt signaling to support embryonic development

BACKGROUND

Energy metabolism disorder or insufficient energy supply during incubation will affect the development and survival of avian embryos. Especially, β-oxidation could not provide the continuous necessary energy for avian embryonic development due to the increasing energy demand under hypoxic conditions during the mid-late embryonic stages. The role and mechanism of hypoxic glycolysis replacing β-oxidation as the main source of energy supply for avian embryonic development in the mid-late stages is unclear.

RESULTS

Here, we found that in ovo injection with glycolysis inhibitor or γ-secretase inhibitor both decreased the hepatic glycolysis level and impaired goose embryonic development. Intriguingly, the blockade of Notch signaling is also accompanied by the inhibition of PI3K/Akt signaling in the embryonic primary hepatocytes and embryonic liver. Notably, the decreased glycolysis and impaired embryonic growth induced by the blockade of Notch signaling were restored by activation of PI3K/Akt signaling.

CONCLUSIONS

Notch signaling regulates a key glycolytic switch in a PI3K/Akt-dependent manner to supply energy for avian embryonic growth. Our study is the first to demonstrate the role of Notch signaling-induced glycolytic switching in embryonic development, and presents new insight into the energy supply patterns in embryogenesis under hypoxic conditions. In addition, it may also provide a natural hypoxia model for developmental biology studies such as immunology, genetics, virology, cancer, etc.

The fatty acid profile in the yolk and yolk sac from incubated goose eggs depends on the breeder' age and laying period

The study analysed the content of fatty acids in the lipids of the yolk and yolk sac of hatching eggs obtained from geese in four reproductive flocks and three laying periods at different incubation dates. A total of 1080 hatching eggs were used in the study (90 eggs from each age group in three laying periods). The geese were kept on one farm under the same conditions. On days 0, 16, 22, and 28 of incubation, the yolk/yolk sac was sampled. Saturated and unsaturated (mono- and poly-) fatty acids were determined, including myristic acid, palmitic acid, palmitoleic acid, margaric acid, stearic acid, oleic acid, linoleic acid, α-linolenic acid, behenic acid, eicosapentaenoic acid. The ratio of unsaturated to saturated fatty acids was calculated. Embryo fatty acid utilisation in eggs from different age groups of geese was similar. The fatty acid profile depended mostly on the laying period. The different proportions of fatty acids in the yolk during incubation indicated changes in the activity of various enzymatic processes in the membrane of the yolk sac of embryos from the beginning and at the end of the laying period. When analysing the interactions between the age of the parent flock and the laying period, the most significant effect on the most FA was found in fresh eggs. On d 16 of lay the myristic, stearic, LA, and behenic acids and PUFA; on d 22 of lay ALA, and on day 28th palmitoleic and margaric acids were depended on this interaction.

Enhancing gosling growth and secretion of somatotrophic and thyrotrophic axis hormones through egg turning during incubation

1. Growth performance of Yangzhou geese hatched from eggs with turning angles of 50° or 70° was evaluated in association with serum hormones and somatotrophic gene mRNA expression.2. Egg turning at 70° significantly (P< 0.05) increased hatchability, gosling quality and hatching weight. Gosling post-hatch body weight, leg and breast muscle weight in the 70° turning group was significantly heavier until 50 d of age.3. Serum concentrations of GH were significantly higher until 30 d of age in the 70° turning group goslings, and those of IGF-I and T3 were higher from hatching to 50 d of age.4. The mRNA expression of GHRH, pituitary GH, liver and leg muscle IGF-I were all significantly higher at 1 and 30 d of age after hatch, but not at 70 d after hatch, in the 70° turning group.5. Egg turning at 70° during incubation improves embryo and gosling quality and growth performance through up-regulation of gene expression and secretion of somatotrophic axis hormones, GHRH, GH and IGF-I, as well as T3.

Monochromatic Green Light Stimulation during Incubation Alters Hepatic Glucose Metabolism That Improves Embryonic Development in Yangzhou Goose Eggs

The influence of monochromatic green light stimulation on hatching performance and embryo development has been studied in chickens, but not geese. The liver has crucial functions in the regulation of energy metabolism during embryogenesis, but its involvement in green light transduction is still unidentified. We aimed to determine the influence of monochromatic green light on Yangzhou goose hatching performance and embryo development. We also investigated the metabolomics and transcriptomic responses of the embryonic liver to green light to determine the underlying molecular mechanisms. Eggs were incubated under either 12 h of monochromatic green light/dark (12 L:12D) cycles or 24 h of darkness (0G:24D). Green light promoted embryonic development and hatching performance, also affected the expression of myogenic regulatory factors associated with muscle development. It also shortened hatching time and elevated plasma levels of growth hormone and insulin-like growth factor-1. Metabolomics and transcriptomic results revealed differentially expressed genes and metabolites with enhanced gluconeogenesis/glycolysis and increased plasma glucose and pyruvate levels under green light. Hence, the growth-promoting effect possibly through regulating energy metabolism in the liver and myogenic regulatory factors in muscle. Our findings provide important and novel insights into the mechanisms underlying the beneficial effects of green light on goose embryos.

The age of the geese from the parent flock and the laying period affect the features of the eggs

The study aimed to assess the goose hatching egg features in four reproductive seasons from 3 stages of laying. Three hundred sixty eggs were used in the study from geese in the first, second, third, and fourth laying season. From each group, 90 eggs were analyzed (30 eggs from the beginning, the peak, and the end of the laying cycle). The structure of the egg and morphological and physical features of the yolk, albumen, and eggshell were analyzed. It was shown that the weight and structure of eggs increased, but the shape index was lower in 2-yr-old geese, as well Haugh's units decreased. The yolk share was lower in the first year, but albumen and eggshell were higher than in other groups. The eggshell whiteness was higher in the first year than in the second, and third. The pores’ quantity was higher in the first year in the blunt and equatorial parts, but the total number in the egg was the highest in the fourth year. The yolk, albumen, and eggshell' density increased with the age. Changes in laying periods were inversely proportional to the changes shown depending on the layers’ age. Geese's age and laying period impact the eggs’ features. Based on the egg quality features, the incubation conditions could be adapted, as well as it can be treated as an indicator of the effectiveness of hatching and goslings quality. Research has shown that the biological value of hatching eggs changes with the age of the geese and the laying period.