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

SIMPLE SUMMARY: The yolk of poultry eggs is the primary source of energy for embryonic development and the only source of lipids for embryonic tissue growth. In our previous studies on improving goose egg hatchability, we demonstrated that a wider 70° egg turning angle significantly increased hatchability and promoted embryonic growth as compared to the traditional 45° or 50° angles. However, the yolk utilization and the associated molecular mechanism, along with improved goose embryonic development, are not clear. In this research, we found that wider-angle egg turning during incubation upregulated the expression of genes related to lipolysis and fat digestion enzymes, as well as genes related to lipid transportation. The upregulation of these genes facilitates the efficient utilization of lipids that are stored in the yolk. We suggest that a wider egg turning angle, 70°, should be used in goose egg incubation to improve hatching performance and gosling quality. ABSTRACT: We aimed to investigate how wide-angle turning of eggs during incubation affected yolk utilization and the associated molecular mechanism, along with improved goose embryonic development. In total, 1152 eggs (mean weight: 143.33 ± 5.43 g) were divided equally and incubated in two commercial incubators with tray turning angles adjusted differently, to either 50° or 70°. Following incubation under the standard temperature and humidity level, turning eggs by 70° increased embryonic days 22 (E22), embryo mass, gosling weight at hatching, and egg hatchability, but reduced E22 yolk mass compared with those after turning eggs by 50°. Lipidomic analyses of the yolk revealed that egg turning at 70° reduced the concentrations of 17 of 1132 detected total lipids, including diglycerides, triglycerides, and phospholipids. Furthermore, the 70° egg turning upregulated the expression of genes related to lipolysis and fat digestion enzymes, such as lipase, cathepsin B, and prosaposin, as well as apolipoprotein B, apolipoprotein A4, very low-density lipoprotein receptor, low-density lipoprotein receptor-related protein 2, and thrombospondin receptor, which are genes involved in lipid transportation. Thus, a 70° egg turning angle during incubation enhances yolk utilization through the upregulation of lipolysis and fat digestion-related gene expression, thereby promoting embryonic development and improving egg hatchability and gosling quality.