Supplementation of reduced protein diets with L-arginine and L-citrulline for broilers challenged with subclinical necrotic enteritis. 3. Immunological parameters and gene expression

Abstract

<p><b>Context.</b> The impact of necrotic enteritis (NE) on acute-phase proteins, interleukins, blood mineral profiles, and gene expression have not been well documented. <b>Aims.</b> This study aimed to determine the effects of L-arginine (Arg) or L-citrulline (Cit) supplementation on serum immunological parameters, serum mineral composition and gene expression in broilers fed reduced-protein diets (RP) during subclinical NE challenge. <b>Methods.</b> Ross 308 cockerels (<i>n </i>= 720) were randomly assigned to six experimental treatments, with eight replicates of 15 birds per pen. The treatments were standard protein without and with NE challenge (SP−, SP+); reduced protein (2% points lower crude protein) without and with NE challenge (RP−, RP+), RP plus added Arg (103% of Ross 308 requirement) with NE challenge (RPA+) and RPC+ where supplemental Arg in RPA+ was replaced with Cit. A 2 × 2 factorial arrangement was employed for the first four treatments. Additionally, treatments SP+, RP+, RPA+, and RPC+ were analysed by one-way ANOVA. <b>Key results</b>. The NE × protein interactions indicated that serum calcium concentration decreased in birds fed the RP diets only when challenged with NE (<i>P </i>< 0.05). The NE × protein interactions showed that the NE challenge downregulated the mRNA expression of jejunal y+ L amino acid transporter-2, and mucin 2 only in birds fed the RP diets (<i>P </i>< 0.05). Feeding the RP decreased expression of catenin alpha 1, but increased expression of claudin 5 and tight junction protein genes compared with the SP (<i>P </i>< 0.05). Birds in the RPC+ treatment had increased gene expression of tight junction protein and claudin 5 compared with the SP+ treatment (<i>P </i>< 0.05). <b>Conclusions.</b> Dietary protein level and infection with NE both have an impact on immune response and expression of genes involved in immunity and nutrient digestibility. In part replacement of Arg with Cit in the RPC diet may have beneficial effects on gene expression in NE-challenged birds. <b>Implications. </b>Feeding RP diets may alleviate a decline in growth during subclinical NE by increasing gene expression of tight junction proteins compared with the SP diets</p>