Supplementation of reduced protein diets with

Abstract

Context. Improving immune status through nutritional adjustments may be part of an effective strategy to reduce reliance on antibiotic growth promoters for controlling necrotic enteritis (NE) in broiler chickens. Aims. This study examined the effect of dietary protein level and the replacement of crystalline L-arginine (Arg) with L-citrulline (Cit) in the reduced-protein diet on the performance of broilers challenged with subclinical NE. Methods. Ross 308 cockerels (n = 720) were randomly allocated to six dietary treatments, with eight replicates of 15 birds per pen, during a 35-day feeding experiment. The treatments were as follows: standard protein without NE challenge (SP−); standard protein with NE challenge (SP+); reduced protein (two percentage points lower crude protein) without NE challenge (RP−); reduced protein with NE challenge (RP+); RP+ plus added Arg (103% of RP, RPA+) and RPC+ where supplemental Arg in RPA+ was replaced with Cit. The first four treatments were considered as a 2 × 2 factorial arrangement, with factors being NE (− or +) and protein level (SP or RP). Treatments SP+, RP +, RPA+, and RPC+ were analysed by one-way ANOVA. Key results. Subclinical NE challenge reduced feed intake (FI), reduced body weight gain (BWG) and increased feed to gain ratio (FCR) from Day 0 to Day 35, increased intestinal lesion scores on Day 16, and reduced relative breast yield on Day 35 (P < 0.05). Feeding RP diets increased FI (P < 0.001), increased BWG (P < 0.01) and reduced FCR (P < 0.01) during the grower phase compared with SP diets when birds were challenged with NE. Birds in the RPC+ treatment had a lower overall FCR than did those in the SP+ treatment (P < 0.001). Birds in the RPA+ treatment had similar FI, BWG and FCR to those in the RP+ treatment (P > 0.05). Conclusions. Collectively, the results showed protective effects of replacing the supplemental Arg with Cit against NE in RP diets, as indicated by higher performance during and after the challenge. Implications. Feeding the RP diets supplemented with Cit may be part of an effective strategy to reduce reliance on antibiotic growth promoters for controlling NE in broiler chickens.

Supplementation of reduced protein diets with

“…However, feeding the RP diets resulted in a higher expression of CLDN5 and TJP1 than feeding the SP diets. This result was consistent with the increased growth performance in RP-fed birds compared with those offered the SP diet, as reported in the first part of this series (Dao et al 2022a).…”

“…villus area, and increases in gut permeability compared with the unchallenged group, as reported in previous parts of this series (Dao et al 2022a(Dao et al , 2022b. Reduced Ca and P digestibility was also reported in NE-infected birds compared with the uninfected birds by Paiva et al (2014).…”

“…Similarly, necrotic enteritis downregulated various nutrient-related genes examined in the current study including PepT1, EEAT3, and PRKAG2. This was consistent with the reduced feed efficiency and impaired jejunal morphology (reduced villus height, villus height to crypt depth ratio, and apparent villus area) observed in NE-challenged birds compared with unchallenged birds, as has been reported in previous parts of this series (Dao et al 2022a(Dao et al , 2022b. Various nutrient transporters are located on the tip of the villi (Obst and Diamond 1992).…”

“…Citrulline supplementation to the RP+ treatment also increased expression of CLDN5 and TJP1, which are important tight junction proteins regulating nutrient absorption and homeostasis. Thus, the upregulation of PRKAG2, CLDN5, and TJP1 genes might partly explain the higher feed efficiency in challenged birds fed the RPC diets than in those fed the SP diets, as reported in the first part of this series (Dao et al 2022a). Additional supplementation of Arg and Cit to the RP diet for challenged birds did not affect jejunal MUC2 expression in the present study.…”

“…Arginine and Cit were supplemented to the RP diets at the expense of wheat. More detailed information on the feed analysis was provided in the first part of this series (Dao et al 2022a).…”