Spirulina platensis Inclusion Reverses Circulating Pro-inflammatory (Chemo)cytokine Profiles in Broilers Fed Low-Protein Diets

Abstract

Proteins are considered the most expensive nutrients in commercial modern broiler production, and their dietary inclusion at low levels is pivotal to minimize feed costs and reduce nitrogen waste. The quest for an environmentally friendly source of proteins that favor the formulation of low protein diets without compromising broiler health, welfare, and growth performance has become a hotspot in nutrition research. Due to its high protein content, the naturally growing Spirulina microalgae is considered a promising nutrient source. The purpose of the present study was, therefore, to determine the effects of Spirulina supplementation on liver bacterial translocation, hematological profile, and circulating inflammatory and redox markers in broilers fed a low-protein diet. One-day-old Ross 708 male broilers (n = 180) were randomly assigned into one of three experimental treatments: standard diet as a control, low protein diet, and low protein diet supplemented with 100 g/kg of Spirulina. Target molecular markers were measured in the peripheral blood circulation using real-time quantitative PCR. Reducing dietary proteins increased bacterial translocation and systemic inflammation as indicated by proportions of basophils among blood leukocytes. The expression levels of circulating pro-inflammatory cytokines [interleukin (IL)-3, IL-6, IL-4, IL-18, and tumor necrosis factor-α], chemokines (CCL-20), and NOD-like receptor family pyrin domain containing 3 inflammasome were significantly upregulated in birds fed the low protein diet compared with the control. The inclusion of Spirulina reversed these effects, which indicates that Spirulina reduces systemic inflammation- and bacterial translocation-induced by a low protein diet and could be a promising alternative protein source in poultry diets.

Keywords: Spirulina; broilers; chemokines; cytokines; inflammasome; inflammation; low protein diet.

Figure 1

Effects of Spirulina on circulating cytokine expression profile. Relative mRNA abundance of circulating IL-6 (A), IL-3 (B), IL-18 (C), and IL-4 (D) in broilers on day (d) 37 were determined by real-time qPCR. Treatments include standard corn/soy (SCP) diet as control and low crude protein without (LCP) or with Spirulina (SP-LCP). Data are presented as mean ± SEM (n = 8/group). Means with different letters are significantly different (P < 0.05).

Figure 2

Effects of Spirulina on circulating TNFα, C3, CRP, and IL-10 expression. Relative mRNA abundance of circulating TNF-α (A), C3 (B), CRP (C), and IL-10 (D) expression in broilers on day (d) 37 were determined by real-time qPCR. Treatments include standard corn/soy (SCP) diet as control and low crude protein without (LCP) or with Spirulina (SP-LCP). Data are presented as mean ± SEM (n = 8/group). Means with different letters are significantly different (P < 0.05).

Figure 3

Effects of Spirulina on circulating chemokine expression profile. Relative mRNA abundance of circulating chemokine (C-C motif) ligand 20 (CCL-20) (A), chemokine-like ligand 4 (CCLL-4) (B), chemokine (C-C motif) ligand 4 (CCL-4) (C), and chemokine (C-X-C motif) ligand 14 (CXCL-14) (D) in broilers on day (d) 37 were determined by real-time qPCR. Treatments include standard corn/soy (SCP) diet as control and low crude protein without (LCP) or with Spirulina (SP-LCP). Data are presented as mean ± SEM (n = 8/group). Means with different letters are significantly different (P < 0.05).

Figure 4

Effects of Spirulina on circulating inflammasome expression. Relative mRNA abundance of NOD-like receptor family pyrin domain-containing 3 (NLRP-3) (A), NOD-like receptor family CARD domain-containing 3 (NLRC-3) (B), NOD-like receptor family CARD domain-containing 5 (NLRC-5) (C), and nucleotide-binding oligomerization domain, leucine-rich repeat-containing X1 (NLRX-1) (D) in broilers on day (d) 37 were determined by real-time qPCR. Treatments include standard corn/soy (SCP) diet as control and low crude protein without (LCP) or with Spirulina (SP-LCP). Data are presented as mean ± SEM (n = 8/group). Means with different letters are significantly different (P < 0.05).

Figure 5

Effects of Spirulina on circulating toll-like receptor expression. Relative mRNA abundance of toll-like receptor 3 (TLR-3) (A), toll-like receptor 4 (TLR-4) (B), toll-like receptor 21 (TLR-21) (C), and myeloid differentiation primary response protein 88 (MyD88) (D) in the blood of broilers on day (d) 37 were determined by real-time qPCR. Treatments include standard corn/soy (SCP) diet as control and low crude protein without (LCP) or with Spirulina (SP-LCP). Data are presented as mean ± SEM (n = 8/group). Means with different letters are significantly different (P < 0.05).

Figure 6

Effects of Spirulina on the expression of circulating antioxidant defense system. Relative mRNA abundance of glutathione peroxidase 1 (GPx-1) (A), glutathione peroxidase 3 (GPx-3) (B), superoxide dismutase 1 (SOD1) (C), and superoxide dismutase 2 (SOD2) (D) in the blood of broilers on day (d) 37 were determined by real-time qPCR. Treatments include standard corn/soy (SCP) diet as control and low crude protein without (LCP) or with Spirulina (SP-LCP). Data are presented as mean ± SEM (n = 8/group). Means with different letters are significantly different (P < 0.05).