Influence of light supplement on duck sternal calcification from integrated analysis of metabolome and transcriptome.

Calcification of bones is the critical process of bone development in birds, which is very important for sustaining the normal biological function of bones. Light is one of the vital factors affecting bone development, but whether light intensity affects bone calcification and the underlying mechanism is still unknown. In this study, we used duck sternum as a model to analyze the calcification process under different light regimes. In addition, the underlying mechanism was also illustrated by integrating metabolomics and transcriptome methods. The experiment lasted from 14 to 51 d of duck age. The control group (LP1) kept light intensity 2 lx during the whole experiment. The two light supplement groups (LP2, LP3) were given light with the intensity of 70 lx at different time (14-29 d for LP2, 14-43 d for LP3). Samples were collected at 52 d of duck age. Sternal calcification analysis showed no significant difference in proportion of area of cartilage matrix and trabecular bone in keel tissue among the 3 groups, but the degree of keel calcification in LP3 was higher than in the other 2 groups. Serum metabolomics showed 32 and 28 differentially accumulated metabolites (DAMs) in the 2 comparison groups, LP1 vs. LP3 and LP1 vs. LP2, respectively. Carboxylic acids and derivatives were the most abundant among the DAMs. Sternal transcriptome analysis showed 231 differentially expressed genes (DEGs), including 177 upregulated genes and 54 downregulated genes in group LP1 vs. LP3, and 22 DEGs in group LP1 vs. LP2. Protein-protein interaction (PPI) network analysis on DEGs between LP1 and LP3 showed that genes BTRC, GLI1, BMP4, and FOS were in the core position of the interaction network, and are also involved in bone development. KEGG pathway analysis of DAMs and DEGs showed that differences in Hedgehog signaling pathway, MAPK signaling pathway, apoptosis, energy metabolism, and amino acid metabolism following light treatment seem likely to have contributed to the observed difference in calcification of duck sternum.

Transcriptome analysis of the bursa of Fabricius and thymus of laying ducks reveals immune gene expression changes underlying the impacts of stocking densities.

1. The thymus and bursa of Fabricius are important immune organs in poultry as they play essential roles in sustaining the normal immune function to maintain health. The following trial investigated whether the stocking density affected gene expressions in immune organs.2. Jinding ducklings were raised in either low or high density (4 or 8 birds/m2) conditions from four to 14 weeks of age, and were then slaughtered and tissues removed. Samples were subjected to high-throughput sequencing to sequence RNA extraction. After filtering calculations with R software, a total of 508 (thymus) and 1,356 (bursa of Fabricius) differentially expressed genes (DEGs) were identified, suggesting that stocking density has an effect on gene expression in duck immune organs.3. Out of a total of 112 immune factor genes and 112 immune pattern receptor genes in ducks, four thymus and 18 bursa of Fabricius genes were differentially expressed in ducks, which indicated that the change of stocking density could affect the expression of immune genes in poultry.