Dietary strategies to alleviate high-stocking-density-induced stress in broiler chickens – a comprehensive review

Effect of dietary aspirin eugenol ester on the growth performance, antioxidant capacity, intestinal inflammation, and cecal microbiota of broilers under high stocking density

This study was designed to examine the impact of aspirin eugenol ester (AEE) on the growth performance, serum antioxidant capacity, jejunal barrier function, and cecal microbiota of broilers raised under stressful high density (HD) stocking conditions compared with normal density broilers (ND). A total of 432 one-day-old AA+ male broilers were randomly divided into 4 groups: normal density (ND, 14 broilers /m2), high density (HD, 22 broilers /m2), ND + AEE, and HD + AEE. The results of the study revealed a significant decrease in the growth performance of broiler chickens as a result of HD stress (P < 0.05). The total antioxidant capacity (T-AOC) in serum demonstrated a significant decrease (P < 0.05) at both 28 and 35 d. Conversely, the serum level of malondialdehyde (MDA) exhibited a significant increase (P < 0.05). Dietary supplementation of AEE resulted in a significant elevation (P < 0.05) of serum GSH-PX, SOD and T-AOC activity at both 28 and 35 d. Moreover, exposure to HD stress resulted in a considerable reduction in the height of intestinal villi and mRNA expression of tight junction proteins in the jejunum, along with, a significant elevation in the mRNA expression of inflammatory cytokines (P < 0.05). However, the administration of AEE reversed the adverse effects of HD-induced stress on villus height and suppressed the mRNA expression of the pro-inflammatory genes, COX-2 and mPGES-1. Additionally, the exposure to HD stress resulted in a substantial reduction in the α-diversity of cecal microbiota and disruption in the equilibrium of intestinal microbial composition, with a notable decrease in the relative abundance of Bacteroides and Faecalibacterium (P < 0.05). In contrast, the addition of AEE to the feed resulted in a notable increase in the relative abundance of Phascolarctobacterium and enhanced microbial diversity (P < 0.05). The inclusion of AEE in the diet has been demonstrated to enhance intestinal integrity and growth performance of broilers by effectively mitigating disruptions in gut microbiota induced by HD stress.

Stress-Related Gene Expression in Liver Tissues from Laying Hens Housed in Conventional Cage and Cage-Free Systems in the Tropics

Global egg production is mainly based on cage systems, which have been associated with negative effects on the welfare of birds. Stress factors in restrictive production systems can lead to changes in gene transcription and protein synthesis, ultimately impacting the quality of poultry products. The liver serves various metabolic functions, such as glycogen storage, and plays a crucial role in animals' adaptation to environmental changes. Consequently, both internal and external conditions can influence liver functions. The aim of this study was to evaluate the gene expression of AGP, CRP, NOX4, SOD1, CAT, GPX1, SREBF1, and FXR in the liver of laying hens under two different production systems. Liver tissues from Hy-Line Brown hens housed in conventional cage and cage-free egg production systems at 60 and 80 weeks of production were used. mRNA transcript levels were determined by qPCR using the relative quantification method and ACTB as the reference gene. AGP, SOD1, and SREBF1 gene expressions were significantly higher in the conventional cage group at the 60 weeks of production. Furthermore, the mRNA levels of transcripts related to oxidative stress and lipid metabolism were higher in the group of laying hens housed in conventional cages compared to those in cage-free systems. These results suggest differential gene expression of genes related to oxidative stress in liver tissues from hens housed in conventional cages compared to cage-free systems. The conditions of the egg production system can impact the gene expression of oxidative stress and lipid synthesis genes, potentially leading to changes in the metabolism and performance of hens, including egg quality.

Trehalose Supplementation Effects on Growth, Intestinal Morphology, Gut Bacteria, and Footpad Dermatitis of Broiler Chickens Reared at High Density

This study aimed to measure the effects of trehalose (Tre) supplementation on the growth, intestinal morphology, gut bacteria, and footpad dermatitis (FPD) of broiler chickens reared at different stocking densities (SD). Four hundred newly hatched Ross 308 male chicks were randomly allocated to four groups of eight, following a 2 × 2 factorial arrangement in a randomized complete block design using two SDs (normal, 11; high, 14 birds/m2) and two diets: basal with and without 0.5% Tre. Tre supplementation was provided during the starter/grower phase, but not the finisher phase. Data were analyzed using a two-way analysis of variance. We observed no significant effects of SD or Tre, individually or combined, on body weight gain (BWG), feed intake (FI), and feed conversion ratio (FCR) during the starter/grower period. However, high SD decreased both BWG (P < 0.001) and FI (P < 0.05), and increased FCR (P < 0.001), during the finisher period. Whereas Tre reduced FCR (P < 0.05) as a main effect, no combined effect was observed on FCR. Over the total period, high SD negatively affected BWG and FCR (P < 0.001), and Tre significantly reduced FCR, with its effect unaffected by SD. No significant effects of SD or Tre were observed on jejunal morphology. The ileal abundance of Clostridium perfringens (P > 0.05) was not affected by high SD but was significantly reduced by Tre. Neither high SD nor Tre altered Lactobacillus spp. counts; however, high SD increased FPD lesion scores, whereas Tre had no effect. The study showed that Tre supplementation during the starter/grower period improved FCR during the finisher period, possibly by decreasing the abundance of C. perfringens in broiler chickens.

Effects of prebiotics and precision biotics on performance, animal welfare and environmental impact. A review

This review aims to analyze the recent studies about prebiotics and precision biotics, as alternatives to animal growth promoters. These substances improve intestinal health, growth performance and poultry environmental impact. Prebiotics are insoluble fibers, that have no nutritive value, but they promote the growth of positive bacteria, increase the nutrients absorption and modulate the immune response. Instead, precision biotics are carbohydrates with glycosidic linkages, which interact with gut bacteria metabolism, reducing the excretion of nitrogen and consequentially, the poultry environmental impact. In the last years, different studies were published in this field, and for this reason, it is necessary to organize the results found. It was shown that mannan-oligosaccharides and β-glucans increase ileal nutrient digestibility, nitrogen retention and antibodies titers. Inulin, arabinoxylans-derived oligosaccharides, and galacto-oligosaccharides improved intestinal morphology, arranging for a larger absorption surface area. It was reported that prebiotics enhance the colonization of positive bacteria and can reduce the count of Campylobacter colonies. Furthermore, xylo-oligosaccharides are often used in animal feed, due to their ability to form organic acids, which decompose noxious substances, improving litter quality, and consequentially, reducing the environmental impact. Litter quality is a relevant aspect for ammonia emissions and for animal welfare. Whether the litter quality is poor, footpad dermatitis increase, worsening animal welfare and increasing nitrogen emissions to air. Precision biotics select metabolic pathways to modulate amino acid degradation, reintegrating the nitrogen discarded, and reducing the ammonia level in litter. It was also reported an improvement of growth performance and a better animal welfare. In conclusion, prebiotics and precision biotics can have positive effects on animal performance and welfare, and they can be a new strategy to reduce the environmental impact of chickens' farms.

Dietary Supplementation with Chlorogenic Acid Enhances Antioxidant Capacity, Which Promotes Growth, Jejunum Barrier Function, and Cecum Microbiota in Broilers under High Stocking Density Stress

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.

Evaluation of Liquid Organic Acids on the Performance, Chyme pH, Nutrient Utilization, and Gut Microbiota in Broilers under High Stocking Density

This study aimed to evaluate the efficacy of organic acids (OAs) in starter broilers and to investigate whether supplemental OAs could alleviate the high stocking density (HSD) stress condition in grower broilers. A total of 408 1-day-old Arbor Acres broilers were assigned into two groups without or with liquid OAs in the starter phase. In the grower phase, each group in the starter phase was divided into a normal stocking density and an HSD. The OA dose was 0.16% at the starter and grower phases. The results showed that at the starter phase, OAs decreased the chyme pH in gizzard and duodenum and increased the activities of chymotrypsin and α-amylase in the duodenal chyme (p < 0.05). In the grower phase, an HSD decreased the growth performance and the ether extract digestibility (p < 0.01). The supplementation of OAs decreased the chyme pH in the gizzard, proventriculus, and duodenum and increased the lipase and α-amylase activities (p < 0.05). The supplemental OAs increased the dry matter and total phosphorous digestibility and the contents of acetic acids, butyric acids, isovaleric acids, and valeric acids (p < 0.05). For cecal microbial compositions at the genus level, an HSD decreased the relative abundance of Blautia, Norank_f__norank_o__RF39, and Alistipes, while supplemental OAs increased the relative abundance of Norank_f__norank_o__RF39 (p < 0.05). In conclusion, although there were no interaction effects between OAs and stocking densities in the present study, it was clear that the supplementation of OAs has beneficial effects on the chyme pH, enzymes activities, and nutrient digestibility in broilers, while an HSD existed adverse effects on the growth performance, nutrient digestibility, and gut microbiota balance in grower broilers.

Effects of dietary chlorogenic acid on ileal intestinal morphology, barrier function, immune factors and gut microbiota of broilers under high stocking density stress

Aims: The purpose of this research was to assess the effect of chlorogenic acid (CGA) in the diet on ileac structure, barrier function, immunological state, and microbial profile of broiler chickens in a high stocking density (HD) environment. Methods: Four hundred and seventy-six male AA broiler chickens were randomly split into four groups, two with a normal stocking density (ND) of fourteen birds per m² and two with a high stocking density of twenty-two birds per m². Each of the treatments consisted of five replicates. One of the two ND and HD groups received the usual feed, while the other two were given at 1.5 g/kg CGA as part of their dietary regimen. Results: The ND CGA group showed a greater increase in villus height and villus height/crypt depth compared to the ND group at 35 and 42 days. The HD group experienced a greater elevation in villus height due to CGA supplementation than the HD group across days 28, 35, and 42. At day 42, the HD group saw a decline in OCLN and ZO-1 mRNA expression in the ileum, but CGA was able to restore them. The HD group experienced a greater rise in OCLN mRNA than the control HD group when supplemented with CGA. The expression of TNF-α, IL-1β, and IL-6 in the ileum was higher in the HD group, and CGA supplementation enhanced this effect. The HD group experienced a greater rise in IL-10 mRNA expression than the control group following the administration of CGA. The HD group showed reduced alpha diversity and an increase in detrimental microbes such as Turicibacter and Shigella in the gut compared to the ND group, while the HD CGA group saw a reduction in Turicibacter, Shigella, and other harmful microbes. These findings reveal that HD stress suppressed the growth of ileac villi, decreased the expression of tight-junction genes, amplified the expression of inflammatory genes, and disturbed the gut microbiota, ultimately leading to increased intestinal permeability. Conclusion: We conclude that when chickens are given dietary CGA, the disruption of the ileac barrier and increased oxidative damage and inflammation due to HD stress are reduced, which increases ileac integrity and the presence of beneficial intestinal bacteria.

Dietary organic acids ameliorate high stocking density stress-induced intestinal inflammation through the restoration of intestinal microbiota in broilers

Background

High stocking density (HSD) stress has detrimental effects on growth performance, intestinal barrier function, and intestinal microbiota in intensive animal production. Organic acids (OA) are widely used as feed additives for their ability to improve growth performance and intestinal health in poultry. However, whether dietary OA can ameliorate HSD stress-induced impaired intestinal barrier in broilers remains elusive. In this study, a total of 528 one-day-old male Arbor Acres broilers were randomly allocated into 3 treatments with 12 replicates per treatment including 10 birds for normal stocking density and 17 birds for HSD. The dietary treatments were as follows: 1) Normal stocking density + basal diet; 2) HSD + basal diets; 3) HSD + OA.

Results

HSD stress can induce increased levels of serum corticosterone, lipopolysaccharides, interleukin-1β, tumor necrosis factor-α, and down-regulated mRNA expression of ZO-1, resulting in compromised growth performance of broilers (P < 0.05). Dietary OA could significantly reduce levels of serum corticosterone, lipopolysaccharides, interleukin-1β, and tumor necrosis factor-α, which were accompanied by up-regulated interleukin-10, mRNA expression of ZO-1, and growth performance (P < 0.05). Moreover, OA could down-regulate the mRNA expression of TLR4 and MyD88 to inhibit the NF-κB signaling pathway (P < 0.05). Additionally, HSD stress significantly decreased the abundance of Bacteroidetes and disturbed the balance of microbial ecosystems, whereas OA significantly increased the abundance of Bacteroidetes and restored the disordered gut microbiota by reducing competitive and exploitative interactions in microbial communities (P < 0.05). Meanwhile, OA significantly increased the content of acetic and butyric acids, which showed significant correlations with intestinal inflammation indicators (P < 0.05).

Conclusions

Dietary OA ameliorated intestinal inflammation and growth performance of broilers through restoring the disordered gut microbial compositions and interactions induced by HSD and elevating short-chain fatty acid production to inhibit the TLR4/NF-κB signaling pathway. These findings demonstrated the critical role of intestinal microbiota in mediating the HSD-induced inflammatory responses, contributing to exploring nutritional strategies to alleviate HSD-induced stress in animals.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-022-00776-2.

Effect of Dietary Chlorogenic Acid on Growth Performance, Antioxidant Function, and Immune Response of Broiler Breeders under Immune Stress and Stocking Density Stress

Simple Summary

Immune stress and high stocking density stress are two major concerns in poultry production, as they can greatly impair the productive and reproductive performance of chickens with serious economic consequences. Chlorogenic acid has been widely used as a feed additive in poultry production due to its potent antioxidant, anti-inflammatory, antibacterial, and antiviral activities. This study aimed to investigate the effects of dietary chlorogenic acid supplementation on growth performance, antioxidant function, and immune response in broiler breeders exposed to immune stress and high stocking density stress. Our study highlights that chlorogenic acid increased feed intake, downregulated serum corticosterone levels, and altered the immune and antioxidant functions of broiler breeders exposed to immune stress or high stocking density stress. Dietary inclusion of 1 g/kg chlorogenic acid could be used to increase feed intake of broiler breeders and alleviate the effects of immune stress and exposure to high stocking density in poultry.

Abstract

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.