Distinct genes and pathways associated with transcriptome differences in early cardiac development between fast- and slow-growing broilers

Effects of day-of-hatch intramuscular administration of a herbal extract mixture and its re-supplementation in drinking water on growth performance, stress indicators, and antioxidant status of broiler chickens reared under hot summer conditions

Broilers under oxidative stress from high ambient temperatures may benefit from the use of additives that have antioxidant properties. This experiment investigated the efficacy of a herbal extract mixture (HEM; aqueous extracts from Ferula gummosa, Thymus vulgaris, and Trachyspermum copticum) in day-old chicks, injected intramuscular (deep pectoral muscle; (0, 30, 60, and 90 μL/0.1 mL of sterilized and distilled water)), and supplemented in drinking water (0 and 0.25 mL/L) during the rearing period. Broilers were reared in battery cages under summer temperature conditions, with average maximum temperature of 35.5°C, average minimum temperature of 25.5°C, and average relative humidity of 50-60%. A total of 400 1-day-old Ross 308 male broiler chicks were randomly assigned to 8 treatment groups (5 replicates/treatment with 10 birds per replicate). From d1 to d10, the indoor air temperature was adjusted to match fluctuating outdoor summer temperatures, and was set at 30-34°C and 50-60% relative humidity; and from d10 onwards, no adjustments were made. Injection of HEM linearly decreased feed:gain (P = 0.005), heterophile-to-lymphocyte (H/L) ratio (P = 0.007), and serum concentrations of cholesterol (P = 0.008), low-density lipoprotein cholesterol (LDL) (P < 0.001), malondialdehyde (P = 0.005), and cortisol (P = 0.008). The 60 μL of HEM injection produced the best results in terms of final body weight (BW; P = 0.003), overall average daily gain (ADG; P = 0.002), European performance index (P < 0.001), carcass yield (P < 0.001), and serum glutathione peroxidase activity (P < 0.001). Supplementation of HEM in drinking water also increased final BW (P = 0.048), overall ADG (P = 0.047), high-density lipoprotein cholesterol (P = 0.042), and total antioxidant capacity (P = 0.030), while decreasing the H/L ratio (P = 0.004) and serum LDL concentration (P = 0.031). There were interactions between injection and water supplementation for BW (day 24; P = 0.045), carcass yield (day 42; P = 0.014), and serum superoxide dismutase activity (day 42; P = 0.004). In conclusion, administering an injection of HEM at a dose of 60 μL at the time of hatching, followed by supplementation at a dose of 0.25 mL/L via drinking water during the rearing period could be a useful strategy for improving the performance and health status of heat-stressed broiler chickens.

Transcriptomic Study on the Lungs of Broilers with Ascites Syndrome

Although broiler ascites syndrome (AS) has been extensively studied, its pathogenesis remains unclear. The lack of cardiopulmonary function in broilers causes relative hypoxia in the body; hence, the lung is the main target organ of AS. However, the transcriptome of AS lung tissue in broilers has not been studied. In this study, an AS model was successfully constructed, and lung tissues of three AS broilers and three healthy broilers were obtained for RNA sequencing (RNA-seq) and pathological observation. The results showed that 614 genes were up-regulated and 828 genes were down-regulated in the AS group compared with the normal group. Gene Ontology (GO) functional annotation revealed the following up-regulated genes: FABP4, APLN, EIF2AK4, HMOX1, MMP9, THBS1, TLR4, BCL2; and down-regulated genes: APELA, FGF7, WNT5A, CDK6, IL7, IL7R, APLNR. These genes have attracted much attention in cardiovascular diseases such as pulmonary hypertension. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that multiple metabolic processes were enriched, indicating abnormal lung metabolism of AS in broilers. These findings elucidate the potential genes and signal pathways in the lungs of broilers with AS and provide a potential target for studying the pathogenesis and preventing AS.

Expression of genes associated with nutrient uptake in intestines of chickens with different growth potentials show temporal changes but are not correlated with growth

The study was designed to compare the expression of genes that encode proteins located at either the brush border (BB) or basolateral (BL) of the gut epithelium among fast and slow-growing broilers.Six lines of chicks with different growth capacities were used: Ross 708, Hubbard H1 (HH1), Cobb 500, Longnecker's Heritage (LHR), Red-Bro, and the Athens Canadian Randombred Control (ACRB). Birds were sampled between embryonic day (ED) 19 and day 35 post-hatch (PH).Performance parameters indicated that Ross 708, HH1, and Cobb 500 had the highest body weights (BW) while ACRBs had the lowest.Quantitative RT-PCR was performed on 13 genes encoding proteins associated with nutrient processing and uptake. Statistical analysis was carried out (ANOVA) for eight BB genes: Aminopeptidase N (APN), four amino acid transporters, (ATB^o,+, B^oAT, b^o,+AT, EAAT3) a di- and tri- peptide transporter (PepT1), and two sugar transporters (GLUT5 and SGLT1). Analysis of four amino acid transporters (CAT1, CAT2, LAT1, and γ⁺LAT1), and a single sugar transporter (GLUT2) associated with BL was carried out.Four BB associated genes (APN, EAAT3, B^oAT, and b^0,+AT) in the small intestine were negatively correlated with growth.In most cases, genes encoding BB proteins increased in expression over time (P<0.05) in the small intestine, while, in the caeca, the expression decreased (P<0.05). The mRNA of BL-associated proteins showed decreased (P<0.05) expression over time in all gut segments, with exception of GLUT2, which increased in expression in the small intestine.The temporal changes in gene expression were consistent among bird lines and BB associated genes tended to increase over time, while BL associated genes tended to decrease over time. Correlation analysis indicated that mRNA expression of nutrient transporter genes may not be a good predictor of growth potential.

Transcriptome analysis reveals potential mechanisms of the effects of dietary Enteromorpha polysaccharides on bursa of Fabricius in broilers

The present study was conducted to evaluate the effects of dietary supplementation of Enteromorpha polysaccharides (EP) on relative organ weight of broilers, and RNA‐seq technique was used to reveal the potential molecular mechanisms of the positive effects of EP on relative organ weight. A total of 396 1‐day‐old male chicks (Arbor Acres) were randomly assigned to six dietary treatments containing EP at 0 (EP0), 1000 (EP1000), 2500 (EP2500), 4000 (EP4000), 5500 (EP5500), and 7000 (EP7000) mg/kg levels for a 35‐day feeding trial. At the end of feeding trail, six birds (one bird from each replicate cage) were randomly selected from each treatment and then slaughtered for relative organ weight analysis. The results showed that the relative weight of bursa of Fabricius were increased in the EP1000 group (p < 0.05), and then three bursa of Fabricius samples from each group (EP0 and EP1000) were randomly selected for RNA‐seq analysis. The results of RNA‐seq analysis showed that there were 20 differentially expressed genes (DEGs) between EP0 and EP1000 groups, among the DEGs, 6 genes were upregulated and 14 genes were downregulated by EP1000 supplementation (p‐adjust < 0.05). Gene ontology (GO) enrichment analysis suggested that the DEGs were mainly enriched in negative regulation of toll‐like receptor 9 signaling pathway (p‐corrected < 0.05). Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis showed that the DEGs were mainly enriched in phagosome, mitophagy‐animal, Salmonella infection, autophagy‐animal signaling pathways (p‐corrected = 0.081). Taken together, dietary EP supplementation at 1000 mg/kg level promoted the relative weight of bursa of Fabricius may be involved in improving the immune function of broilers. These findings provided a reference for further exploring the specific molecular mechanism of EP that affecting the organ development in broilers.

Transcriptional Changes after Enniatins A, A1, B and B1 Ingestion in Rat Stomach, Liver, Kidney and Lower Intestine

Enniatins (ENs) are depsipeptide mycotoxins produced by Fusarium fungi. They are known for their capacity to modulate cell membrane permeability and disruption of ionic gradients, affecting cell homeostasis and initiating oxidative stress mechanisms. The effect of the acute toxicity of ENs A, A1, B and B1 at two different concentrations after 8 h of exposure was analysed in Wistar rats by a transcriptional approach. The following key mitochondrial and nuclear codified genes related to the electron transport chain were considered for gene expression analysis in stomach, liver, kidney and lower intestine by quantitative Real-Time PCR: mitochondrially encoded NADH dehydrogenase 1 (MT-ND1), mitochondrially encoded cytochrome c oxidase 1 (MT-COX1), succinate dehydrogenase flavoprotein subunit A and ATP synthase F1 subunit alpha, respectively. Moreover, the expression of markers involved in oxidative stresssuperoxide dismutase 1 (SOD1), glutathione peroxidase 1 (Gpx1), heme oxygenase 1, apoptosis B-cell lymphoma 2, Bcl2 Associated protein X (Bax), tumor suppressor protein (p53), inhibition of apoptosis nuclear factor kappa of activated B cells, immune system interleukin 1β and intestinal tight junction Occludin merely in lower intestine tissues have been investigated. For mitochondrial genes, the main differences were observed for MT-ND1 and MT-COX1, showing its deficiency in all selected organs. With regard to the intestinal barrier’s cellular response to oxidative stress, the activity of the antioxidant gene SOD1 was decreased in a dose-dependent manner. Similarly, the catalytic enzyme GPx1 was also downregulated though merely at medium dose employed. On the contrary, the pro-apoptotic Bax and p53 regulators were activated after ENs exposure, reporting a significant increase in their expression. Furthermore, the alteration of intestinal permeability was assessed by the abnormal activity of the tight junction protein occludin. In summary, ENs may generate mitochondrial disorders and induce oxidative stress in intestinal barrier function.

Pathophysiology and pathological remodelling associated with dilated cardiomyopathy in broiler chickens predisposed to heart pump failure

Broiler chickens selected for rapid growth are highly susceptible to dilated cardiomyopathy (DCM). In order to elucidate the pathophysiology of DCM, the present study examines the fundamental features of pathological remodelling associated with DCM in broiler chickens using light microscopy, transmission electron microscopy (TEM), and synchrotron Fourier Transform Infrared (FTIR) micro-spectroscopy. The morphological features and FTIR spectra of the left ventricular myocardium were compared among broiler chickens affected by DCM with clinical signs of heart pump failure, apparently normal fast-growing broiler chickens showing signs of subclinical DCM (high risk of heart failure), slow-growing broiler chickens (low risk of heart failure) and Leghorn chickens (resistant to heart failure, used here as physiological reference). The findings indicate that DCM and heart pump failure in fast-growing broiler chickens are a result of a complex metabolic syndrome involving multiple catabolic pathways. Our data indicate that a good deal of DCM pathophysiology in chickens selected for rapid growth is associated with conformational changes of cardiac proteins, and pathological changes indicative of accumulation of misfolded and aggregated proteins in the affected cardiomyocytes. From TEM image analysis it is evident that the affected cardiomyocytes demonstrate significant difficulty in the disposal of damaged proteins and maintenance of proteostasis, which leads to pathological remodelling of the heart and contractile dysfunction. It appears that the underlying causes of accumulation of damaged proteins are associated with dysregulated auto phagosome and proteasome systems, which, in susceptible individuals, create a milieu conducive for the development of DCM and heart failure. RESEARCH HIGHLIGHTS The light and electron microscopy image analyses revealed degenerative changes and protein aggregates in the cardiomyocytes of chickens affected by DCM. The analyses of FTIR spectra of the myocardium revealed that DCM and heart pump failure in broiler chickens are associated with conformational changes of myocardial proteins. The morphological changes in cardiomyocytes and conformational changes in myocardial proteins architecture are integral constituents of pathophysiology of DCM in fast-growing broiler chickens.