Dietary threonine (Thr) deficiency increases hepatic triglyceride content and reduces sebum and abdominal fat percentages in lean type (LT), but not in fatty type (FT) Pekin ducks.  However, the molecular changes regarding the role of Thr in lipid metabolism in LT and FT ducks induced by Thr deficiency remains unknown.  This study compared differential expression gene profiles related to lipid metabolism in FT and LT Pekin ducks affected by Thr deficiency.  We performed transcriptomic profiling and scanned the gene expression in the liver, sebum, and abdominal fat of Pekin ducks fed either Thr-deficient or Thr-adequate diet for 21 days from 14 to 35 days of age.  There were 187, 52, and 50 differentially expressed genes (DEGs) identified in the liver, sebum, and abdominal fat of LT ducks affected by Thr deficiency, of which 12, 9, and 5 genes were involved in lipid metabolism, respectively.  Thr deficiency altered the expression of 27, 6, and 3 genes in FT ducks’ liver, sebum, and abdominal fat, respectively.  None of the DEGs had a relationship with lipid metabolism in FT ducks.  KEGG analysis showed that the DEGs in the LT ducks’ livers were enriched in lipid metabolism pathways (linolenic acid metabolism, glycerophospholipid metabolism, and arachidonic acid metabolism) and amino acid metabolism pathways (biosynthesis of amino acids, phenylalanine metabolism, β-alanine metabolism, and glycine, serine and threonine metabolisms).  The DEGs in the sebum and abdominal fat of LT ducks were not enriched in lipid and amino acid metabolic pathways.  Additionally, DEGs involved in lipid metabolism were found to be upregulated by Thr deficiency in LT ducks, such as malic enzyme 3 (ME3), acyl-CoA synthetase short-chain family member 2 (ACSS2) in liver, and lipase member M (LIPM) in sebum.  In summary, dietary Thr deficiency regulated the gene expression involved in lipid metabolism in the liver, sebum, and abdominal fat of Pekin ducks in a genotype-dependent manner.

Salmonella Enteritidis (SE) is a zoonotic and vertically transmitted pathogen, often colonized in the reproductive tract of adult poultry, which can result in direct contamination of eggs and threaten human health.  Previous studies have revealed that some pattern recognition receptors and resistance genes were involved in regulating immune responses to SE invasion in birds.  However, the role of these immune response genes was not independent, and the interactions among the genes remained to be further investigated.  In this study, SE burden and colonization were determined in reproductive tissue after the ducks were SE-infected, and RNA-sequencing was performed to construct co-expression networks by weighted gene co-expression network analysis (WGCNA).  The result showed that SE could be isolated from 22% of infected-birds in any segment of the reproductive tract and the SE was readily colonized in the stroma, small follicle, isthmus, and vagina of the reproductive tracts in morbid ducks.  The top central, highly connected genes were subsequently identified three specific modules in the above four tissues at the defined cut-offs (P<0.01), including 60 new candidate regulators and 125 transcription factors.  Moreover, those 185 differentially expressed genes (DEGs) in these modules were co-expressed.  Moreover, the hub genes (TRAF3, CXCR4 and IL13RA1) were identified to act with many other genes through immune response pathways including NF-kappaB, Toll-like receptor, steroid biosynthesis, and p53 signaling pathways.  These data provide references that will understand the immune regulatory relationships during SE infection, but also assist in the breeding of SE-resistant lines through potential biomarkers.