Transcriptomic analysis of genes in the nitrogen recycling pathway of meat‐type chickens divergently selected for feed efficiency

Abstract

The understanding of the dynamics of ammonia detoxification and excretion in uricotelic species is lagging behind ureotelic species. The relative expression of genes involved in nitrogen recycling and feed efficiency in chickens is unknown. The objective of this study was to investigate the transcriptomics differences in key genes in the nitrogen (N) metabolism and purine biosynthesis pathway in a chicken population divergently selected for low (LRFI) or high (HRFI) residual feed intake at days 35 and 42 using duodenum, liver, pectoralis major (P. major) and kidney. There was a significant positive correlation between RFI and fecal N. The purine salvage pathway was activated in the LRFI compared with HRFI at days 42. The birds in the LRFI population attained greater feed efficiency by having lower FI, increasing their protein retention and producing adequate glutamine to maintain growth compared with the HRFI line. To maintain growth, excess N is deaminated mostly to generate purine nucleotides. Generating purine nucleotides primarily from the purine biosynthesis pathway is energetically costly, and to preserve energy, they preferentially generate nucleotides from the purine salvage pathway. The LRFI birds need to generate sufficient nucleotides to maintain growth despite reduced FI that then results in reduced fecal N.

Assessing serum metabolite profiles as predictors for feed efficiency in broiler chickens reared at geographically distant locations

“…Despite not having measured serum insulin levels, elevated serum uric acid and NEFA in high RFI females may confirm our assumption of reduced insulin sensitivity since both metabolites are typically raised during insulin resistance due to increased lipolysis and deamination of amino acids for energy provision (e.g., Yuan et al, 2008;Ji et al, 2012). In addition, raised serum uric acid in high RFI animals may also suggest less efficient nitrogen recycling as recently shown for a different chicken line (Aggrey et al, 2014).…”

“…Our understanding of the physiological mechanisms underlying the FE of chicken's is steadily advancing (e.g., Aggrey et al, 2014;Lee et al, 2015;Zhou et al, 2015). However, the contribution of the rearing environment has not yet been sufficiently elucidated.…”

“…Generally, a chicken population from a commercial breed shows considerable variation in RFI (van Eerden et al, 2004). As knowledge about RFI related physiological mechanisms in poultry and other livestock species advances, the biological basis of inter-animal variations associated with FE becomes clearer (Bottje and Carstens, 2009;Aggrey et al, 2014;Lee et al 2015;Mignon-Grasteau et al, 2015;Zhuo et al, 2015).…”

Feed conversion ratio, residual feed intake and cholecystokinin type A receptor gene polymorphisms are associated with feed intake and average daily gain in a Chinese local chicken population

“…These low RFI individuals can achieve a greater feed efficiency.The reason may be that up-regulated genes were associated with energy metabolism, cell proliferation and fat metabolism [ 39 ]. Previous studies have demonstrated that individuals with a low RFI can maintain growth by increasing protein storage and glutamate synthesis, and achieve higher feed utilization and reduce nitrogen content in excreta [ 20 , 40 ]. Individuals with high RFI were more likely to respond to stress than individuals with low RFI [ 41 , 42 ].…”

Transcriptomic differences of genes in the avian target of rapamycin (avTOR) pathway in a divergent line of meat-type chickens selected for feed efficiency

“…Anthony et al (2002) demonstrated that infusion of both leucine and insulin can enhance TOR signaling. The LRFI chickens retained more nitrogen per feed intake than the HRFI chickens did (Aggrey et al, 2014) and may require a much more efficient system for transporting amino than is needed by the HRFL chickens. The avTORC1 complex comprises avTOR, avLST8, and raptor, and the raptor-TOR interaction regulates TORC1 activity (Wullschleger et al, 2006).…”