Characterization of stress response involved in chicken myopathy.

Myopathies (Woody Breast (WB) and White Striping (WS)) of broiler chickens have been correlated with fast growth. Recent studies reported that localized hypoxia and metabolic impairment may involve in these myopathies of birds. In order to better understand the stress response mechanisms affecting myopathies of broilers, the aim of this study was to examine effects of WB and both WB/WS on stress hormone corticosterone (CORT) levels and expressional changes of stress response genes including glucocorticoid (GC) receptor (GR), 11ß-Hydroxysteroid dehydrogenase type 1 (11ß-HSD1), DNA methylation regulators (DNMTs), and arginine vasotocin receptor 1a and 1b (V1aR, V1bR). Results of radioimmunoassay showed that CORT levels of WB and WB/WS birds were significantly higher compared to Con (p < 0.05), however, the combination of WB/WS was not significantly higher than WB birds, implying that the effects of WB and WS on CORT are not synergistic. Hepatic GR expression of both WB and WB/WS birds were significantly higher compared to Con (p < 0.05). However, GR expression levels in breast muscle of both WB and WB/WS birds were decreased compared to Con (p < 0.05). Hepatic 11ß-HSD1 expression was increased only in WB/WS birds compared to Con birds with no significant difference between Con and WB birds. 11ß-HSD1 expression was decreased and increased in WB and WB/WS birds compared to Con, respectively, in breast muscle (p < 0.05). DNMT1 expression was significantly decreased in both muscle and liver of WB birds, and in muscle of WB/WS birds, but not in liver of WB/WS birds, indicating differential effects of WS on the epigenetical stress response of muscle and liver compared to WB. V1aR expression was significantly increased in muscle of WB birds, and in liver of WB/WS birds compared to Con birds (p < 0.05). V1bR was not changed in muscle and liver of WB birds compared to Con birds. Taken together, results suggest that GC-induced myopathies occur in fast-growing broiler chickens and circulating CORT level might be a significant biochemical marker of myopathies (WB and WS) of birds. In addition, chronic stress responses in breast muscle and tissue-specific epigenetic changes of stress response genes by DNMTs may play a critical role in the occurrence of myopathies.

Blood Plasma Biomarkers for Woody Breast Disease in Commercial Broilers.

Woody breast (WB) myopathy results in poor muscle quality. The increasing incidence of WB over the last several years indicates a need for improved prediction or early diagnosis. We hypothesized that the use of body fluids, including blood, may be more suitable than breast muscle tissue in developing a minimally invasive diagnostic tool for WB detection. To identify potential early-age-biomarkers that may represent the potential onset of WB, blood samples were collected from 100, 4 wks old commercial male broilers. At 8 wks of age, WB conditions were scored by manual palpation. A total of 32 blood plasma samples (eight for each group of WB and non-WB control birds at two time points, 4 wks and 8 wks) were subjected to shotgun proteomics and untargeted metabolomics to identify differentially abundant plasma proteins and metabolites in WB broilers compared to non-WB control (Con) broilers. From the proteomics assay, 25 and 16 plasma proteins were differentially abundant (p < 0.05) in the 4 and 8 wks old samples, respectively, in WB compared with Con broilers. Of those, FRA10A associated CGG repeat 1 (FRAG10AC1) showed >2-fold higher abundance in WB compared with controls. In the 8 wks old broilers, 4 and 12 plasma proteins displayed higher and lower abundances, respectively, in WB compared with controls. Myosin heavy chain 9 (MYH9) and lipopolysaccharide binding protein (LBP) showed more than 2-fold higher abundances in WB compared with controls, while transferrin (TF) and complement C1s (C1S) showed more than 2-fold lower abundances compared with controls. From the untargeted metabolomics assay, 33 and 19 plasma metabolites were differentially abundant in birds at 4 and 8 wks of age, respectively, in WB compared with controls. In 4 wks old broilers, plasma 3-hydroxybutyric acid (3-HB) and raffinose concentrations showed the highest and lowest fold changes, respectively, in WB compared with controls. The blood plasma 3-HB and raffinose concentrations were confirmed with targeted biochemical assays. Blood biomarkers, such as 3-HB and raffinose, may be suitable candidate targets in the prediction of WB onset at early ages.

Intestinal Barrier Integrity in Heat-Stressed Modern Broilers and Their Ancestor Wild Jungle Fowl.

High environmental temperature has strong adverse effects on poultry production, welfare, and sustainability and, thereby, constitutes one of the most challenging stressors. Although colossal information has been published on the effects of heat stress on poultry productivity and gut health, the fundamemntal mechanisms associated with heat stress responses and intestinal barrier function are still not well defined. The aim of the present study was, therefore, to determine the effects of acute (2 h) heat stress on growth performance, gut integrity, and intestinal expression of heat shock and tight junction proteins in slow- (broilers of the 1950's, ACRB), moderate- (broilers of 1990's, 95RAN), rapid-(modern broilers, MRB) growing birds, and their ancestor wild jungle fowl (JF). Heat stress exposure significantly increased the core body temperature of 95RAN and MRB chickens by ~0.5-1°C, but not that of JF and ACRB compared to their counterparts maintained at thermoneutral conditions. Heat stress also depressed feed intake and increased serum fluorescein isothiocyanate-dextran (FITC-D) levels (P < 0.05) in modern broilers (95RAN and MRB) but not in JF and ACRB, indicating potential leaky gut syndrome. Molecular analyses showed that heat stress exposure significantly up regulated the duodenal expression of occludin (OCLN) and lipocalin (LCN2) in ACRB, zonula occludens (ZO-2), villin1 (VIL1), and calprotectin (CALPR) in 95 RAN, and only CALPR in MRB compared to their TN counterparts. In the jejunum however, heat stress down regulated the expression of PALS1-associated tight junction protein (PATJ) in ACRB, 95RAN, and MRB, and that of cadherin1 (CDH1) in MRB. In the ileum, heat stress significantly down regulated the expression of OCLN in 95 RAN, ZO-1 in MRB, gap junction protein alpha1 (GJA1) in JF, and VIL1 in ACRB compared to their TN counterparts. In summary, this is the first report, to our knowledge, showing that tight junction protein expression is environmental-, genotype-, and intestinal segment-dependent and identifying molecular signatures, such as CDH1, CALPR, and ZO-1, potentially involved in leaky gut syndrome-induced by heat stress in MRB.