Characterizing Woody Breast Myopathy in a Meat Broiler Line by Heat Production, Microbiota, and Plasma Metabolites

Abstract

Selection for quantitative traits in meat broilers such as breast yield and growth rate exert physiological pressure leading to ante mortem histological and biochemical alterations in muscle tissues. The poultry industry has recently witnessed a myopathy condition affecting Pectoralis major (breast muscle) of broilers, called woody breast (WB), an etiology still unclear to scientific community. A study was conducted to characterize the WB myopathy in a meat broiler line at its finishing phase (d 41) in terms of heat production (HP), microbiota and plasma metabolites. Two treatment groups were studied-WB affected (myopathy) and normal (non-myopathy) broiler; n = 20 in each group. Indirect calorimetry was utilized for HP measurement. Furthermore, body composition (BC) analysis was also performed using dual-energy x-ray absorptiometry (DEXA). Microbiota in ileal digesta was studied with PCR amplified 16s rRNA gene. LC-MS targeted metabolomics was performed to understand differential expression of plasma metabolites. Results showed that there was difference in fasting HP (P < 0.05) between these two treatment groups, with non-myopathy broiler producing more heat which was indicative of higher body protein content validated by higher protein: fat ratio by BC results. Less protein content in myopathy bird could be due to probable higher mixed muscle degradation occurring in lean tissue as marked by elevated 3-methylhistidine expression in plasma. Microbiota results showed unclassified Lactobacillus as predominant genus with higher abundance occurring in myopathy group; whereas at species level, L. acidipiscis was predominant bacteria for non-myopathy broiler. Differentially significant metabolites (P < 0.05) identified from plasma metabolome between these two treatment groups were homocysteine, cyclic GMP, trimethylamine N-oxide (TMAO), tyramine, carnitine, and acetylcarnitine, which were all associated to cardiovascular system. The findings suggest that more research in meat broilers could be opted toward delivering reduced vascularity issues to alleviate this myopathy condition.

In vivo collagen and mixed muscle protein turnover in 2 meat-type broiler strains in relation to woody breast myopathy

“…Decreased protein synthesis and increased degradation is a physiological phenomenon that may contribute to muscle protein loss, whereas the proteolytic pathways (ubiquitin-proteasome, lysosomal, and calpain) may be more evident in enhanced degradation of muscle tissue ( Khalil et al., 2018 ; McCarthy and Murach, 2019 ; Maharjan et al., 2020b ). Furthermore, both strains had higher FDR values for myopathy-affected broilers than for nonmyopathy broilers, which was also validated by the relatively higher expression of 3-MH in plasma samples in myopathy-affected broilers for both strains ( Maharjan et al., 2020c ). Strain B had greater expression of 3-MH when compared between strains indicating higher mixed muscle degradation occurring than in strain A.…”

“…3-MH Is considered a unique biomarker of myofibrillar protein breakdown, and its appearance level in blood or urine is indicative of the degree of breakdown occurring in muscle tissue ( Williamson et al., 1977 ; Tipton et al., 2018 ). Furthermore, Maharjan et al. (2020c) recently reported that myopathy-affected broilers had a differential expression of plasma metabolites that showed potential involvement of vascularity issues causing the poor arterial blood circulation in muscle tissue leading to localized hypoxia and increased muscle degradation and myodegeneration.…”

“…For calculating predictive FSR values, WB scores and the corresponding FSR values were cumulated for each replicate broiler, and then the FSR values were obtained for each sampling age after the WB scores were normalized to WB score value of 1. The linear positive relationship was applied for obtaining predictive FSR values for WB scores of 2 and 3 ( Maharjan et al., 2020c ).…”

“…Targeted metabolomics of 3-MH was performed on a triple quadrupole MS coupled to an I-class UPLC system (Waters) for differential expression. Procedures for handling plasma samples in a laboratory, data processing, and bioinformatics were carried out as described in the article by Maharjan et al., 2020c .…”

Effect of Pre-Blended Phosphates on the Freezing Quality Characteristics of Ground Woody Breast Meat Compared to Normal Meat

“…On a histological level, WB myofibrils have degeneration with necrosis and accumulating fibrosis (interstitial connective tissue) and lipidosis [ 7 , 8 ]. From a biochemical perspective, WB fillets are found to be higher in fat, moisture, and collagen, and lower in protein and ash [ 9 , 10 ]. The physiological and biochemical changes in the meat lead to poor texture, lower water holding capacity (WHC), higher drip loss, and poor eating quality.…”