Size and components of poult yolk sacs

Goose Embryonic Development, Glucose and Thyroid Hormone Concentrations, and Eggshell Features Depend on Female Age and Laying Period

This study aimed to evaluate embryonic development; analyze the glucose, triiodothyronine (T3), and thyroxine (T4) concentrations in the blood of embryos and goslings; and assess the structure and temperature (EST) of the eggshell. The eggs that were analyzed were from four laying seasons of White Kołuda® geese at three periods (90 eggs × 4 groups × 3 periods). The different embryo proportions, fetal membranes in the egg, and sizes of internal organs indicate a different growth rate and degree of embryo development depending on the laying age and laying period. The goose age influenced the hormone concentrations in the embryos' blood on the 28th day of incubation, which supports a relationship between the females' age and development. The eggshell thickness and density change depending on the laying age and the laying period. A decrease in eggshell thickness in the eggs up to the third season was found after the 16th day of incubation (simultaneously, the density showed an increasing trend). A lower EST distinguished the eggs from the oldest geese in the first half of the hatch. The formation of the chorioallantois membrane was associated with an increase in EST in the oldest geese.

The regulation of IMF deposition in pectoralis major of fast- and slow- growing chickens at hatching

Background

The lipid from egg yolk is largely consumed in supplying the energy for embryonic growth until hatching. The remaining lipid in the yolk sac is transported into the hatchling’s tissues. The gene expression profiles of fast- and slow-growing chickens, Arbor Acres (AA) and Beijing-You (BJY), were determined to identify global differentially expressed genes and enriched pathways related to lipid metabolism in the pectoralis major at hatching.

Results

Between these two breeds, the absolute and weight-specific amounts of total yolk energy (TYE) and intramuscular fat (IMF) content in pectoralis major of fast-growing chickens were significantly higher (P < 0.01, P < 0.01, P < 0.05, respectively) than those of the slow-growing breed. IMF content and u-TYE were significantly related (r = 0.9047, P < 0.01). Microarray analysis revealed that gene transcripts related to lipogenesis, including PPARG, RBP7, LPL, FABP4, THRSP, ACACA, ACSS1, DGAT2, and GK, were significantly more abundant in breast muscle of fast-growing chickens than in slow-growing chickens. Conversely, the abundance of transcripts of genes involved in fatty acid degradation and glycometabolism, including ACAT1, ACOX2, ACOX3, CPT1A, CPT2, DAK, APOO, FUT9, GCNT1, and B4GALT3, was significantly lower in fast-growing chickens. The results further indicated that the PPAR signaling pathway was directly involved in fat deposition in pectoralis major, and other upstream pathways (Hedgehog, TGF-beta, and cytokine–cytokine receptor interaction signaling pathways) play roles in its regulation of the expression of related genes.

Conclusions

Additional energy from the yolk sac is transported and deposited as IMF in the pectoralis major of chickens at hatching. Genes and pathways related to lipid metabolism (such as PPAR, Hedgehog, TGF-beta, and cytokine–cytokine receptor interaction signaling pathways) promote the deposition of IMF in the pectoralis major of fast-growing chickens compared with those that grow more slowly. These findings provide new insights into the molecular mechanisms underlying lipid metabolism and deposition in hatchling chickens.

Electronic supplementary material

The online version of this article (10.1186/s40104-017-0207-z) contains supplementary material, which is available to authorized users.

Incubation temperature influences trade-off between structural size and energy reserves in mallard hatchlings

The reproductive success of precocial birds depends on investments in clutch formation and incubation. Egg quality strongly affects the phenotypic traits correlated with survival of the hatchling, but parental ability to maintain incubation temperature can also influence hatchling outcomes. The effect of incubation temperature on hatchling phenotype has been widely studied in reptiles but not in birds. The aim of this study was to explore the effects of egg mass and incubation temperature on the incubation period, hatchability, and hatchling phenotype of the mallard (Anas platyrhynchos). Mallard eggs were incubated under six constant incubation temperatures (ranging from 35.0° to 39.0°C). Hatchlings were weighed, and their structural size was measured. Some hatchlings were used for an examination of residual yolk sac mass and basic chemical composition of the yolk-free body. All investigated phenotypic traits except for chemical composition were positively correlated with egg mass. Incubation temperature did not affect hatchling body mass, but increased temperatures led to a decreased yolk-free body mass and structural size of hatchlings and to increased yolk sac mass. Our results suggest that there is a trade-off between the yolk-free body size and energetic reserves in the form of the yolk sac and that this trade-off is modulated by incubation temperature.