Chlorogenic acids (CGA) are widely used as feed additives for their ability to improve growth performance and intestinal health in poultry. However, whether dietary CGAs could reverse the impaired intestinal condition caused by high stocking density (HD) in broiler chickens is unknown. We determined the effect of dietary CGA on growth, serum antioxidant levels, jejunum barrier function, and the microbial community in the cecum of broilers raised under normal (ND) or HD conditions. HD stress significantly decreased growth and body weight, which was restored by CGA. The HD group showed increased serum malondialdehyde, an oxidative byproduct, and decreased SOD and GSH-Px activity. CGA reduced malondialdehyde and restored antioxidant enzyme activity. HD stress also significantly decreased jejunal villus length and increased crypt depth. Compared with ND, the expression of tight-junction genes was significantly decreased in the HD group, but this decrease was reversed by CGA. HD also significantly upregulated TNF-α. Compared with ND, the cecal microbiota in the HD group showed lower alpha diversity with increases in the harmful bacteria Turicibacter and Shigella. This change was altered in the HD + CGA group, with enrichment of Blautia, Akkermansia, and other beneficial bacteria. These results demonstrated that HD stress decreased serum antioxidant capacity, inhibited the development of jejunal villi, and downregulated expression of tight-junction genes, which increased intestinal permeability during the rapid growth period (21 to 35 days). Dietary CGA enhanced antioxidant capacity, improved intestinal integrity, and enhanced beneficial gut bacteria in chickens raised under HD conditions.

The study was conducted to evaluate the effects of dietary chlorogenic acid supplementation on the growth performance, antioxidant function, and immune response of broiler breeders exposed to immune stress or high stocking density stress. The test was divided into two stress models. For the immune stress test, 198 birds were distributed into three experimental treatments with six replicates per treatment. The treatments were: (1) saline control (birds injected with saline and fed basal diet), (2) LPS group (birds injected with 0.5 mg LPS/kg body weight and fed basal diet), and (3) CGA + LPS group (birds injected with LPS and fed basal diet supplemented with 1 g/kg CGA. LPS was intraperitoneally injected from day 14, and then daily for 10 days. For the high stocking density stress model, 174 birds were distributed into three experimental treatments with six replicates per treatment. The treatments were: (1) controls (birds fed basal diet and raised at a stocking density of 14 broilers per m²), (2) high-density group (birds fed with basal diet and raised at a stocking density of 22 broilers per m²), and (3) high density + CGA group (birds fed with 1 g/kg CGA and raised at a stocking density of 22 broilers per m²). Results showed that LPS injection and high stocking density significantly decreased the body weight and feed intake of broiler breeders, while CGA supplementation increased feed intake of broiler breeders under LPS injection and high stocking density stress. Moreover, LPS injection and high stocking density increased the concentration of corticosterone in serum, and CGA addition remarkably downregulated serum corticosterone levels. The GSH level decreased with LPS injection and CGA increased the GSH concentration in the intestines of immune-stressed broiler breeders. LPS injection promoted the production of circulating proinflammatory cytokines (serum IL-1β and TNF-α) by 72 h after LPS injection. Dietary supplementation with CGA prevented the increase in serum TNF-α caused by LPS. These results suggest that dietary inclusion of 1 g/kg CGA could increase the feed intake of broiler breeders and alleviate the effects of inflammatory mediator stress and exposure to high stocking density.

The search for effective in-feed antibiotic alternative is growing due to the global trend to reduce or ban the utilization of antibiotics as growth promotors in poultry diets. This study was processed to assess the effect of dietary refined functional carbohydrates (RFCs) replacing antibiotic growth promoters (AGP) on growth performance, intestinal morphologic structure and microbiota, as well as intestinal immune function and barrier function of broilers reared on a commercial broilers farm. Trials contained 3 treatments with 4 replicate broiler houses, with about 25,000 birds each room. The treatments were control group (CON), RFCs group (CON + 100 mg/kg RFCs), and AGP group (CON + 50 mg/kg bacitracin methylene disalicylate (BMD), respectively. Results showed that RFCs and AGP group significantly increased (P < 0.05) average daily gain (ADG) during d 22 to 45 in contrast to control. Compared with the control and AGP-treated groups, feeding RFCs increased (P < 0.05) jejunal villus height to crypt depth ratio. AGP addition reduced (P < 0.05) the jejunal villi surface area compared to broilers fed control and RFC supplemented diets. Supplementation of RFCs promoted (P < 0.05) the growth of Lactobacillus but inhibited Escherichia coli and Salmonella proliferation compared with the control group. Inclusion of RFCs and BMD enhanced (P < 0.05) antibody titers against avian influenza virus H9 compared with control. RFCs and AGP both down-regulated (P < 0.05) intestinal TLR4 mRNA levels, whereas RFCs tended to up-regulate (P = 0.05) IFN-γ gene expression compared to control. Expression of intestinal tight junction genes was not affected by either AGP or RFCs supplementation. Based on above observation, we suggested that RFCs could replace in-feed antibiotic BMD in broiler diets for reducing intestinal pathogenic bacteria and modulating immunity of broilers.

This study aimed to evaluate the effects of aspirin eugenol ester (AEE) on growth performance, oxidative liver damage, inflammation, and liver metabolomics in broilers under high-stocking-density (HSD) stress. A total of 360 broilers were divided into four groups: normal density (ND, 14/m²), high density (HD, 22/m²), ND-AEE (ND + 0.01% AEE), and HD-AEE (HD + 0.01% AEE). HSD decreased total antioxidant capacity, increased malondialdehyde (MDA) levels, and elevated the expression of cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase-1 (mPGES-1) mRNA, which contributed to the reduced performance of broilers. Specifically, HSD caused abnormalities in linoleic acid metabolism, leading to elevated levels of Prostaglandin E2 (PGE2) and Leukotriene B4 (LTB4) synthesis, which aggravated inflammation, increased liver lipid levels, and impaired ATP production. AEE counteracted the decline in broiler production performance induced by HSD by enhancing total antioxidant capacity, reducing MDA levels, protecting the liver from oxidative damage, and maintaining mitochondrial oxidative phosphorylation. AEE positively regulated the linoleic acid metabolism by promoting the synthesis of γ-linolenic acid and phosphatidylcholine, which reduced the synthesis of COX-2 and mPGES-1. AEE alleviated the metabolic imbalance caused by HSD stress and enhanced the efficiency of mitochondrial fatty acid oxidation, which reduced excess lipid accumulation in the liver and promoted ATP production. In summary, this study provides strong support for the dietary addition of AEE to alleviate liver oxidative damage, inflammation, and energy metabolism disorders caused by HSD stress.

High stocking density (HSD) stress is a serious risk factor for poor animal health and loss of commercial productivity that affects broiler farms globally. While HSD can increase production efficiency and reduce costs, it can also lead to aggressive behavior and competition among the animals, unequal resource distribution, increased stress, disease, and loss of meat quality. Under HSD stress conditions, the redox balance is disrupted, inflammatory responses are exacerbated, immune function is impaired, and susceptibility to disease increases. This study reviewed the effects of HSD on the health of broilers, analyzing and prioritizing the associated physiological and biochemical changes. This review focuses on broiler chickens. HSD can have multiple adverse effects on poultry health, and this review evaluates nutritional strategies aimed at alleviating the negative effects of HSD stress to enhance welfare and productivity. By synthesizing current evidence, this review highlights the impacts of HSD on broiler health and welfare and identifies opportunities for nutritional interventions to mitigate these effects. This review provides a comprehensive reference for future research of HSD stress in poultry.

Broilers grown in a high-density (HD) stocking environment may experience intense competition that may adversely affect their growth relative to animals reared at a normal density (ND). The growth performance of HD broilers is increased by aspirin eugenol ester (AEE), although the mechanism by which this compound modulates hypothalamus-regulated feeding behavior is unclear. The aims of this study were to determine the effects of including AEE in the basal diet on the hypothalamic transcriptome and to examine in parallel the impact of these modifications on broiler production performance in HD conditions. Three hundred sixty one-day-old male Arbor Acres broilers were randomly divided into four groups: an ND group (14 broilers/m²), HD group (22 broilers/m²), ND-AEE group, and HD-AEE group. Each treatment group had 10 replicates, with 7 broilers per replicate in the ND and ND-AEE groups and 11 broilers per replicate in the HD and HD-AEE groups. Broiler growth performance was monitored, and hypothalamus samples were collected for transcriptome analysis on day 28. The HD group exhibited a reduced body weight (p < 0.01) at this timepoint compared to the ND group. However, the addition of AEE significantly improved average daily feed intake, average daily gain, and feed conversion ratio in the HD group from days 22 to 28 compared to the HD group without AEE (p < 0.05). The transcriptome results showed that 20 signaling pathways were commonly enriched among the groups (ND vs. HD, HD vs. HD-AEE). Several potential candidate genes were identified as involved in chicken central nervous system development and regulation of feed intake. Thus, the current study provides new insights into hypothalamic transcription patterns that are associated with the ameliorative effects of AEE in HD broilers.