Metabolic and microbiota response to arginine supplementation and cyclic heat stress in broiler chickens

Abstract

Little attention has been paid to the biological role of arginine and its dietary supplementation in broilers under heat stress (HS) conditions. Therefore, the main aim of this study was to assess the response of broilers to arginine supplementation and cyclic HS, with a focus on liver, pectoral muscle, and blood metabolic profiles and the cecal microbiota. Day-old male Ross 308 broilers (n = 240) were placed in 2 rooms with 12 pens each for a 44-day trial. Pens were assigned to one of two groups (6 pens/group/room): the control group (CON) was given a basal diet in mash form and the treated group (ARG) was fed CON diet supplemented with crystalline L-arginine. The total arginine:lysine ratio of CON diet ranged between 1.02 and 1.07, while that of ARG diet was 1.20. One room was constantly kept at thermoneutral (TN) conditions, while the birds in the other room were kept at TN conditions until D34 and subjected to cyclic HS from D35 onwards (∼34°C; 9:00 A.M.-6:00 P.M.). Blood, liver, Pectoralis major muscle, and cecal content were taken from 2 birds per pen (12 birds/group/room) for metabolomics and microbiota analysis. Growth performance data were also collected on a pen basis. Arginine supplementation failed to reduce the adverse effects of HS on growth performance. Supplemented birds showed increased levels of arginine and creatine in plasma, liver, and P. major and methionine in liver, and reduced levels of glutamine in plasma, liver, and P. major. HS altered bioenergetic processes (increased levels of AMP and reduced levels of fumarate, succinate, and UDP), protein metabolism (increased protein breakdown to supply the liver with amino acids for energy production), and promoted the accumulation of antioxidant and protective molecules (histidine-containing dipeptides, beta-alanine, and choline), especially in P. major. Arginine supplementation may have partially counterbalanced the effects of HS on energy homeostasis by increasing creatine levels and attenuating the increase in AMP levels, particularly in P. major. It also significantly reduced cecal observed diversity, while HS increased alpha diversity indices and affected beta diversity. Results of taxonomic analysis at the phylum and family level are also provided.

Keywords: arginine; breast muscle; broiler chicken; heat stress; liver; metabolism; microbiota; plasma.

FIGURE 1

Publication trend (A) and type (B) of papers mentioning or focusing on arginine in heat-stressed broilers. Note: The literature search was carried out by searching the Scopus database on September 12, 2022 entering the following query string: {TITLE [(chicken OR broiler) AND (arginine OR arg) AND heat AND stress AND NOT (arginine AND vasopressin) AND NOT plant AND NOT polymorphism] OR ABS [(chicken OR broiler) AND (arginine OR arg) AND heat AND stress AND NOT (arginine AND vasopressin) AND NOT plant AND NOT polymorphism]}. No restriction on the date and type of publication was set.

FIGURE 2

Hourly temperature (A–I) of the two rooms during the cyclic HS period. Note: D#, day#; TN, thermoneutral conditions; HS, (cyclic) heat stress conditions; TND#, data logger# in room TN; HSD#, data logger# in room HS.

FIGURE 3

Rectal temperature of CON and ARG birds in the two rooms on the first (A) and eighth (B) day of the cyclic HS period at two time points. Note: The rectal temperature of 18 labeled birds/group/room was measured on the first (D35) and the eighth (D42) day of the cyclic HS period at two time points, namely T1 (9:00 AM) and T2 (6:00 P.M.). Group means are the black dots inside the boxes. **, p < 0.01; ***, p < 0.001; ****, p < 0.0001. TN, thermoneutral conditions; HS, (cyclic) heat stress conditions; T1/2, time point 1/2; D#, day#; CON, control group; ARG, arginine-supplemented group.