Cecal microbiota contribute to the development of woody breast myopathy

Changes in gene expression in the intestinal mucus of broilers with woody breast myopathy

Previous work has shown that dietary treatments affect woody breast (WB) incidence differently, which indicates that gut conditions such as gut barrier function, inflammation, and oxidative stress are likely related to WB. In this study, dietary supplementation with antibiotics (bacitracin) or probiotics (Bacillus subtilis) was investigated for their effects on the expression of transcripts related to gut barrier function, inflammation, and oxidative stress in the mucus lining of the jejunum from broilers with or without WB. A split-plot experimental design was used in this study. The dietary treatments served as the main plot factor and the breast muscle condition was the subplot factor. On d 41, jejunum mucus was collected from 1 bird from each of 3 replicate pens in each 3 dietary treatment groups that exhibited WB and an additional bird that contained a normal breast (3 biological replicates/treatment/phenotype; 3 × 3 × 2, total N = 18). Total RNA was extracted using a commercial RNA extraction kit. The expression levels of CLDN1, MUC6, TLR2A, TLR2B, TLR4, IFN-γ, IL-1β, IL-8L1, IL-10, NOS2, and SOD were determined using 2-step RT-qPCR analysis. The gene expression difference in ΔCt values was determined after normalizing with the chicken 18S rRNA gene. When the significant differences occurred between treatments, the relative fold change was calculated using the ΔΔCt method and the significance level was calculated. The PROC GLM procedure of SAS 9.4 was used, and the level of significance was set at P ≤ 0.05. There were no significant interactive effects between diet and the breast muscle condition on the expression of any of the genes tested. However, birds with WB exhibited higher MUC6 (P < 0.0001) gene expression levels than birds with normal breast muscles. In addition, the expression of SOD decreased in birds that were fed the antibiotic diet when compared to birds that were fed the probiotic diet (P = 0.014). In conclusion, WB identified in broilers tested in the current study is attributed to increased expression of mucin, indicating a correlation between WB incidence and gel-forming mucin secretion and pathogen signaling.

Study of emerging chicken meat quality defects using OMICs: What do we know?

Starting in approximately 2010, broiler breast meat myopathies, specifically woody breast meat, white striping, spaghetti meat, and gaping have increased in prevalence in the broiler meat industry. Omic methods have been used to elucidate compositional, genetic, and biochemical differences between myopathic and normal breast meat and have provided information on the factors that contribute to these myopathies. This review paper focuses on the genomic, transcriptomic, proteomic, metabolomic, and other omics research that has been conducted to unravel the molecular mechanisms involved in the development of these myopathies and their associated factors and potential causes. SIGNIFICANCE: This review manuscript summarizes poultry meat quality defects, also referred to as myopathies, that have been evaluated using omics methods. Genomics, transcriptomics, proteomics, metabolomics and other methodologies have been used to understand the genetic predisposition, the protein expression, and the biochemical pathways that are associated with the expression of woody breast meat, white striping, and other myopathies. This has allowed researchers and the industry to differentiate between chicken breast meat with and without myopathic muscle as well as the environmental and genetic conditions that contribute to differences in biochemical pathways and lead to the phenotypes associate with these different myopathies.

Multi-Omics Analysis of the Microbiome and Metabolome Reveals the Relationship Between the Gut Microbiota and Wooden Breast Myopathy in Broilers

Wooden breast (WB) is a widely prevalent myopathy in broiler chickens. However, the role of the gut microbiota in this myopathy remains largely unknown, in particular the regulatory effect of gut microbiota in the modulation of muscle metabolism. Totally, 300 1-day-old Arbor Acres broilers were raised until 49 days and euthanized, and the breast filets were classified as normal (NORM), mild (MILD), or severe wooden breast (SEV). Birds with WB comprised 27.02% of the individuals. Severe WB filets had a greater L* value, a* value, and dripping loss but a lower pH (P < 0.05). WB filets had abundant myofiber fragmentation, with a lower average myofiber caliber and more fibers with a diameter of <20 μm (P < 0.05). The diversity of the intestinal microflora was decreased in birds with severe WB, with decreases in Chao 1, and observed species indices. At the phylum level, birds with severe WB had a lower Firmicutes/Bacteroidetes ratio (P = 0.098) and a decreased abundance of Verrucomicrobia (P < 0.05). At the species level, gut microbiota were positively correlated with 131 digesta metabolites in pathways of glutamine and glutamate metabolism and arginine biosynthesis but were negatively correlated with 30 metabolites in the pathway of tyrosine metabolism. In plasma, WB induced five differentially expressed metabolites (DEMs), including anserine and choline, which were related to the severity of the WB lesion. The microbial-derived metabolites, including guanidoacetic acid, antiarol, and (2E)-decenoyl-ACP, which entered into plasma were related to meat quality traits and myofiber traits. In summary, WB filets differed in gut microbiota, digesta, and plasma metabolites. Gut microbiota respond to the wooden breast myopathy by driving dynamic changes in digesta metabolites that eventually enter the plasma.

Effects of dietary bacitracin or Bacillus subtilis on the woody breast myopathy-associated gut microbiome of Eimeria spp. challenged and unchallenged broilers

Study suggested that dysbiosis of the gut microbiota may affect the etiology of woody breast (WB). In the current study, the cecal microbiota and WB in chickens fed three different diets were investigated. A total of 504 male chicks were used in a randomized complete block design with a 3 (Diet) × 2 (Challenge) factorial arrangement of treatments with 6 replicates per treatment, 6 treatments per block, and 14 birds per treatment. The experimental diets were a control diet (corn-soybean meal basal diet), an antibiotic diet (basal diet + 6.075 mg bacitracin/kg feed), and a probiotic diet (basal diet + 2.2 × 10⁸ CFU Bacillus subtilis PB6/kg feed). On d 14, birds that were assigned to the challenge treatment received a 20 × live cocci vaccine. On d 41, breast muscle hardness in live birds was palpated and grouped into normal (NB) and WB phenotypes. Cecal contents were collected and their bacterial compositions were analyzed and compared. The genomic DNA of the cecal contents was extracted and the V3 and V4 regions of 16S rRNA gene were amplified and sequenced via an Illumina MiSeq platform. There were no differences (P > 0.05) in Shannon and Chao 1 indexes between the challenges, diets, and phenotypes (NB vs. WB). However, there was a difference (P = 0.001) in the beta diversity of the samples between the challenged and nonchallenged groups. Relative bacterial abundance differed (false discovery rate, FDR < 0.05) between the challenge treatments, but there were no significant differences (FDR > 0.05) among the three diets or two phenotypes. Predicted energy metabolism, nucleotide metabolism, and amino acid and coenzyme biosynthesis activities only differed (q-value < 0.05) between challenged and nonchallenged groups. The cocci challenge altered the gut microbial composition on Butyricicoccus pullicaecorum, Sporobacter termitidis, and Subdoligranulum variabile, but the dietary antibiotic and probiotic treatments did not impact gut microbial composition. No strong association was found between WB myopathy and gut microbial composition in this study.

Role of diet-microbiota interactions in precision nutrition of the chicken: facts, gaps, and new concepts

In the intestine, host-derived factors are genetically hardwired and difficult to modulate. However, the intestinal microbiome is more plastic and can be readily modulated by dietary factors. Further, it is becoming more apparent that the microbiome can potentially impact poultry physiology by participating in digestion, the absorption of nutrients, shaping of the mucosal immune response, energy homeostasis, and the synthesis or modulation of several potential bioactive metabolites. These activities are dependent on the quantity and quality of the microbiota alongside its metabolic potential, which are dictated in large part by diet. Thus, diet-induced microbiota alterations may be harnessed to induce changes in host physiology, including disease development and progression. In this regard, the gut microbiome is malleable and renders the gut microbiome a candidate 'organ' for the possibility of precision nutrition to induce precision microbiomics-the use of the gut microbiome as a biomarker to predict responsiveness to specific dietary constituents to generate precision diets and interventions for optimal poultry performance and health. However, it is vital to identify the causal relationships and mechanisms by which dietary components and additives affect the gut microbiome which then ultimately influence avian physiology. Further, an improved understanding of the spatial and functional relationships between the different sections of the avian gut and their regional microbiota will provide a better understanding of the role of the diet in regulating the intestinal microbiome.

Bacitracin, Bacillus subtilis, and Eimeria spp. challenge exacerbates woody breast incidence and severity in broilers

Woody breast (WB) is a myopathy that is related to the increasing growth rate. Understanding the influence of management factors on WB formation and development is important to minimize WB. This study was conducted to define how management factors affect broiler growth performance, processing yield, and WB incidence. Ross × Ross 708 chicks were randomly assigned to a 3 (diet) × 2 (cocci challenge) × 2 (sex) factorial arrangement of treatments. The 3 dietary treatments were: control diet (corn-soybean meal basal diet), antibiotic diet (basal diet + 6.075 mg bacitracin /kg feed), and probiotic diet (basal diet + 2.2 × 10⁸ CFU Bacillus subtilis PB6/kg feed). Birds in cocci challenge treatments received 20 × live cocci vaccine on d 14. The hardness of breast muscle in live birds was determined by palpation and grouped into Normal, Slight, Moderate, and Severe categories. Across diet and sex treatments, the cocci challenge resulted in decreases in body weight (BW) on d 29 and 35 (P < 0.0001 and = 0.032) in body weight gain (BWG) from d 14 to 29 (P < 0.0001). However, an increase of BW occurred on d 35 (P = 0.032) and an increase of BWG occurred from d 29 to 35 and d 35 to 43 (P = 0.0001 and 0.002), and the cocci challenge increased WB incidence on d 29 (P = 0.043) and d 43 (P = 0.013). Across challenge and sex treatments, birds fed the antibiotic diet exhibited a higher growth rate (GR) than those fed the control or probiotic diet from d 0 to 14 (P = 0.016), but not after d 14 (P > 0.05). Across sex, the antibiotic and probiotic diets increased WB incidence for those birds that did not receive a cocci challenge on d 43 (P = 0.040). Across challenge and diet treatments, males exhibited a higher BW, BWG, and GR throughout all growth phases, and males showed a higher WB incidence on d 29, 35, and 43 (P = 0.002, P < 0.0001, and P = 0.0002, respectively). In conclusion, bacitracin and Eimeria spp. increased WB incidence, BW, and GR. However, Bacillus subtilis increased WB incidence in male broilers without affecting BW and GR.