Abstract
BackgroundThough intensive genetic selection has led to extraordinary advances in growth rate and feed efficiency in production of meat-type chickens, endocrine processes controlling these traits are still poorly understood. The anterior pituitary gland is a central component of the neuroendocrine system and plays a key role in regulating important physiological processes that directly impact broiler production efficiency, though how differences in pituitary gland function contribute to various growth and body composition phenotypes is not fully understood.ResultsGlobal anterior pituitary gene expression was evaluated on post-hatch weeks 1, 3, 5, and 7 in male broiler chickens selected for high (HG) or low (LG) growth. Differentially expressed genes (DEGs) were analyzed with gene ontology categorization, self-organizing maps, gene interaction network determination, and upstream regulator identification to uncover novel pituitary genes and pathways contributing to differences in growth and body composition. A total of 263 genes were differentially expressed between HG and LG anterior pituitary glands (P ≤ 0.05 for genetic line-by-age interaction or main effect of line; ≥1.6-fold difference between lines), including genes encoding four anterior pituitary hormones. Genes involved in signal transduction, transcriptional regulation, and vesicle-mediated transport were differentially expressed and are predicted to influence expression and secretion of pituitary hormones. DEGs involved in immune regulation provide evidence that inflammation and response to cellular stressors may compromise pituitary function in LG birds, affecting their ability to adequately produce pituitary hormones. Many DEGs were also predicted to function in processes that regulate organ morphology and angiogenesis, suggesting pituitary gland structure differs between the divergently selected lines.ConclusionsThe large number of DEGs within the anterior pituitary gland of birds selected for high or low body weight highlights the importance of this gland in regulating economically important traits such as growth and body composition in broiler chickens. Intracellular signaling, transcriptional regulation, and membrane trafficking are important cellular processes contributing to proper hormone production and secretion. The data also suggest that pituitary function is intimately tied to structure, and organization of the gland could influence hypothalamic and systemic metabolic inputs and delivery of hormones regulating growth and metabolism into peripheral circulation.
Highlights
Though intensive genetic selection has led to extraordinary advances in growth rate and feed efficiency in production of meat-type chickens, endocrine processes controlling these traits are still poorly understood
While intensive genetic selection within the broiler industry has led to rapid advances in growth rate, body composition, and feed efficiency, there is still a lack of understanding related to endocrine control of growth and metabolism in these animals
As animal production systems are forced to reduce the use of antibiotics due to consumer demand and regulatory requirements, understanding biological mechanisms governing growth and metabolism in broiler chickens is crucial to maintaining production efficiency
Summary
Though intensive genetic selection has led to extraordinary advances in growth rate and feed efficiency in production of meat-type chickens, endocrine processes controlling these traits are still poorly understood. The HWS and LWS lines have been continually selected for over 50 generations and differ almost 10-fold in body weight at the age of selection (8 weeks) [4, 5, 7] They have been widely used to investigate growth, metabolism, and feed intake in broiler chickens. Transcriptional profiling of abdominal fat in the two lines suggests that HG birds express higher levels of transcription factors linked to adipogenesis, while LG birds exhibit increased expression of transcripts for genes that promote energy expenditure and are involved in hemostasis [15] In addition to these molecular and endocrine differences, several quantitative trait loci for growth [20], metabolism and body composition [21], and breast meat quality [22] have been identified through use of the HG and LG lines. We have used this population for the discovery of additional neuroendocrine factors that regulate growth and body composition
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