High incidence of cardiac arrhythmias in broiler chickens

Histopathological Findings in the Cardiovascular System of Psittacidae in Routine Diagnostics

Samples of 363 Psittacidae were included in this study with a focus on cardiovascular diseases. These were identified in 28.9% of the animals, with pericarditis and/or epicarditis and myocarditis representing approximately half of all lesions and bacteria being the most common infectious cause. Cardiac lymphoma was only seen in 5 birds, whereas degenerative vascular lesions were diagnosed in 26.7% of the cases. Histopathology in the context of clinical findings and complementary examination results is the most useful tool for the evaluation of cardiac diseases.

Sudden death syndrome in broiler chickens: a review on the etiology and prevention of the syndrome

Sudden death syndrome (SDS) is a condition in which apparently healthy broiler chickens die suddenly. There are short convulsions and frantic wing-beating prior to death, and the weight of internal organs is the same as in healthy chickens. The exact etiology of SDS is unknown. Heart problems have been implicated as a potential cause of the disease in broiler chickens. Despite considerable research, effective methods of prevention are still being sought. Furthermore, the prophylactic measures often make production less profitable (reduced body weight gain resulting from restricted feeding) and prolong the growth period. It is necessary to continue research on SDS, in particular on stimulation of the cardiovascular system to reduce the susceptibility of broilers to sudden death syndrome under intensive production systems.

Feed Restriction Induced Changes in Behavior, Corticosterone, and Microbial Programming in Slow- and Fast-Growing Chicken Breeds

Simple Summary

Different genotypes of slow- and fast-growing chickens have phenotypic changes in appearance, behavior, and productivity in response to artificial selection. Feed restriction and gut microbiota play a vital role in controlling food intake, nutrition, and health. However, little is known about how feed restriction, as a benefit or chronic stress, influences behavior, stress response, and gut microbial programming in slow- and fast-growing chickens. This study aimed to explore slow- and fast-growing chickens who had feed restricted to 70% of ad libitum or were given ad libitum feed for 30 days to evaluate the effects on behavior, stress response, and gut microbiota. We found that feed restriction can influence behaviors in both slow- and fast-growing breeds. Feed restriction to 70% for 30 days can influence stress response and gut microbiota composition, but some changes are evident only in slow- or only in fast-growing chickens. The study provides a better understanding of how artificial selection has affected chicken biology and their response to stress challenge.

Abstract

This study aimed to explore the difference between two Chinese local broilers, one slow- and one fast-growing, in their response to a stress challenge. We conducted the study on slow- (Weining chicken) and fast-growing (Jinlinghua chicken) breeds, with 50 chickens from each breed either feed restricted to 70% for 30 days as a stress or given ad libitum to evaluate the effects on behavior, corticosterone, and microbial programming. Standing behavior was more frequent while exploration was less common in fast-growing breeds compared to slow-growing breeds. Food seeking and ingestion, exploration, and drinking increased, while resting decreased in the feed restricted treatments. There was no difference in corticosterone concentration between slow- and fast-growing chickens, but the level was affected by feeding treatments, and the interaction of breed and feed restriction. At the genus-level, the relative abundance of Bacteroides and Lactobacillus was higher, while Cloacibacillus and Megasphaera was lower in the slow-growing breed compared to the fast-growing breed. Feed restricted birds had a higher abundance of Mucispirillum, but lower abundance of Cloacibacillus, Clostridium XlVa and Clostridium IV. In conclusion, feed restriction to 70% for 30 days as a chronic stress stimulation caused more activity, elevated the stress response, and altered gut microbiota composition, but some changes were only evident in slow- or fast-growing chickens.

The effect of supplementary ultraviolet wavelengths on the performance of broiler chickens

Qualities of the light environment, such as the spectral composition of light, have been shown to impact growth and performance of broiler chickens. UVA light is visible to broiler chickens, whereas UVB wavelengths promote endogenous vitamin D synthesis, which could support their rapid development. The aim of the current study was to investigate the impacts of supplementary UVA and UVB wavelengths on performance indicators of broiler chickens. Day-old Ross 308 chicks (n = 638), reared to a target stocking density of 33 kg/m², were randomly assigned to 1 of 3 lighting treatments: A) White light emitting diode (LED) and supplementary UVA LED lighting (18-h photoperiod); B) White LED with supplementary UVA and UVB fluorescent lighting providing 30 μW/cm² UVB at bird level (lights on for 8 h of the total photoperiod to avoid overexposure of UVB); and C) White LED control group, representative of farm conditions (18-h photoperiod). Mortality was recorded, and broiler chickens were individually weighed at 8, 15, 22, 27, and 34 D of age. Generalized linear models and nonlinear mixed effects models (Gompertz curve) were fitted to determine the effects of UV wavelengths on broiler mortality and growth performance. UV did not impact breast or leg weight of broiler chickens but was associated with differences in mortality, growth, and end weight. Broiler chickens provided with UVA for the full 18-h photoperiod had slower initial growth than control broilers and a reduction in mortality. Results from male broilers reared with supplementary UVA + UVB for 8 h indicated they could reach finishing weights sooner than controls, which supports the potential for UVA + B to improve the growth performance of males. Results suggest that the provision of supplementary UVA + UVB wavelengths may improve the performance of male broiler chickens. The reduction in mortality in the UVA only treatment may warrant further investigation. The inclusion of UV wavelengths within poultry lighting regimes represents a promising area of further study.

iTRAQ-based proteomic analysis reveals key proteins affecting cardiac function in broilers that died of sudden death syndrome

Sudden death syndrome (SDS), which is a cardiac-related condition commonly observed in chickens selected for rapid growth, causes significant economic losses to the global poultry industry. Its pathogenesis in broilers is poorly understood, and little is known about the proteome of the heart tissue of SDS broilers. A quantitative proteomic approach using isobaric tags for relative and absolute quantification labeling of peptides was used to characterize the protein expression profiles in the left ventricle of SDS broilers. These proteins were further analyzed by bioinformatics, and two proteins were validated by western blot analysis. We identified 186 differentially expressed proteins (DEPs), of which 72 were upregulated, and 114 were downregulated in the SDS group. Functional annotation suggested that 7 DEPs were related to cardiac muscle contraction, and another 7 DEPs were related to cardiac energy metabolism. Protein interaction network predictions indicated that differences in cardiac muscle contraction between SDS and healthy groups were regulated by troponin T, tropomyosin alpha-1 chain, fast myosin heavy chain HCIII, myosin-1B, coronin, and myoglobin, whereas differences in cardiac energy metabolism and biosynthesis of amino acids were regulated by gamma-enolase, phosphoglycerate mutase, NADH-ubiquinone oxidoreductase chain 2, serine/threonine-protein kinase, myoglobin, and alpha-amylase. Our expression profiles provide useful information and new insights into key proteins to elucidate SDS for further studies.

Genome-wide association scan for QTL and their positional candidate genes associated with internal organ traits in chickens

Background

Poultry breeding programs have been focused on improvement of growth and carcass traits, however, this has resulted in correlated changes in internal organ weights and increased incidence of metabolic disorders. These disorders can affect feed efficiency or even cause death. We used a high density SNP array (600 K, Affymetrix) to estimate genomic heritability, perform genome-wide association analysis, and identify genomic regions and positional candidate genes (PCGs) associated with internal organ traits in an F2 chicken population. We integrated knowledge of haplotype blocks, selection signature regions and sequencing data to refine the list of PCGs.

Results

Estimated genomic heritability for internal organ traits in chickens ranged from low (LUNGWT, 0.06) to high (GIZZWT, 0.45). A total of 20 unique 1 Mb windows identified on GGA1, 2, 4, 7, 12, 15, 18, 19, 21, 27 and 28 were significantly associated with intestine length, and weights or percentages of liver, gizzard or lungs. Within these windows, 14 PCGs were identified based on their biological functions: TNFSF11, GTF2F2, SPERT, KCTD4, HTR2A, RB1, PCDH7, LCORL, LDB2, NR4A2, GPD2, PTPN11, ITGB4 and SLC6A4. From those genes, two were located within haplotype blocks and three overlapped with selection signature regions. A total of 13,748 annotated sequence SNPs were in the 14 PCGs, including 156 SNPs in coding regions (124 synonymous, 26 non-synonymous, and 6 splice variants). Seven deleterious SNPs were identified in TNFSF11, NR4A2 or ITGB4 genes.

Conclusions

The results from this study provide novel insights to understand the genetic architecture of internal organ traits in chickens. The QTL detection performed using a high density SNP array covered the whole genome allowing the discovery of novel QTL associated with organ traits. We identified PCGs within the QTL involved in biological processes that may regulate internal organ growth and development. Potential functional genetic variations were identified generating crucial information that, after validation, might be used in poultry breeding programs to reduce the occurrence of metabolic disorders.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-6040-3) contains supplementary material, which is available to authorized users.

Sequence and expression analysis of cardiac ryanodine receptor 2 in broilers that died from sudden death syndrome

Sudden death syndrome (SDS) is a stress-related disease in broilers with no diagnostic clinical or necropsy findings. SDS is associated with ventricular tachycardia (VT) and ventricular fibrillation (VF); however, its pathogenesis is not precisely described at the molecular level. Dysfunction of ryanodine receptor 2 (RYR2), that controls rapid release of Ca²⁺ from the sarcoplasmic reticulum (SR) into the cytosol during muscle contraction, has been associated with VT and sudden cardiac death (SCD) in human patients with structurally normal heart, but there is no report describing abnormalities in RYR2 in diseased broilers. In order to advance our knowledge on the molecular mechanisms predisposing broilers to fatal arrhythmia, the present study was conducted to determine the occurrence of possible mutations and changes in the expression level of the chicken RYR2 gene (chRYR2) in broilers that died from SDS. An increase in mRNA expression level and nine novel point mutations in chRYR2 were found in relation to SDS. In conclusion, susceptibility to lethal cardiac arrhythmia in SDS may be associated with specific changes in intracellular Ca²⁺ cycling components such as RYR2 due to mutation and dysregulation. Finding the probable association of SDS with gene defects can be applied to select for chickens with lower susceptibility to SDS and decrease the poultry industry losses due to SDS mortality. RESEARCH HIGHLIGHTS Investigation of the occurrence of possible mutations and changes in the expression level of chicken RYR2 gene (chRYR2) in broilers that died from SDS. Increase in the mRNA expression level of chRYR2 in relation to SDS. Nine novel point mutations in chRYR2 of broilers that died from SDS. Possible connection between susceptibility to lethal cardiac arrhythmia in SDS and changes in intracellular Ca²⁺ cycling machinery, such as RYR2, due to mutation and dysregulation.

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

Modern fast-growing broilers are susceptible to cardiac dysfunctions because their relatively small hearts cannot adequately meet the increased need of pumping blood through a large body mass. To improve cardiac health in broilers through breeding, we need to identify the genes and pathways that contribute to imbalanced cardiac development and occurrence of heart dysfunction. Two broiler lines–Ross 708 and Illinois–were included in this study as models of modern fast-growing and heritage slow-growing broilers, respectively. The left ventricular transcriptome were compared between the two broiler lines at day 6 and 21 post hatch through RNA-seq analysis to identify genes and pathways regulating compromised cardiac development in modern broilers. Number of differentially expressed genes (DEGs, p<0.05) between the two broiler lines increased from 321 at day 6 to 819 at day 21. As the birds grew, Ross broilers showed more DEGs (n = 1879) than Illinois broilers (n = 1117). Both broilers showed significant change of muscle related genes and immune genes, but Ross broilers showed remarkable change of expression of several lipid transporter genes including APOA4, APOB, APOH, FABP4 and RBP7. Ingenuity pathway analysis (IPA) suggested that increased cell apoptosis and inhibited cell cycle due to increased lipid accumulation, oxidative stress and endoplasmic reticulum stress may be related to the increased cardiac dysfunctions in fast-growing broilers. Cell cycle regulatory pathways like “Mitotic Roles of Polo-like Kinases” are ranked as the top changed pathways related to the cell apoptosis. These findings provide further insight into the cardiac dysfunction in modern broilers and also potential targets for improvement of their cardiac health through breeding.

Transcriptome analysis reveals potential mechanisms underlying differential heart development in fast- and slow-growing broilers under heat stress

BACKGROUND

Modern fast-growing broilers are susceptible to heart failure under heat stress because their relatively small hearts cannot meet increased need of blood pumping. To improve the cardiac tolerance to heat stress in modern broilers through breeding, we need to find the important genes and pathways that contribute to imbalanced cardiac development and frequent occurrence of heat-related heart dysfunction. Two broiler lines - Ross 708 and Illinois - were included in this study as a fast-growing model and a slow-growing model respectively. Each broiler line was separated to two groups at 21 days posthatch. One group was subjected to heat stress treatment in the range of 35-37 °C for 8 h per day, and the other was kept in thermoneutral condition. Body and heart weights were measured at 42 days posthatch, and gene expression in left ventricles were compared between treatments and broiler lines through RNA-seq analysis.

RESULTS

Body weight and normalized heart weight were significantly reduced by heat stress only in Ross broilers. RNA-seq results of 44 genes were validated using Biomark assay. A total of 325 differentially expressed (DE) genes were detected between heat stress and thermoneutral in Ross 708 birds, but only 3 in Illinois broilers. Ingenuity pathway analysis (IPA) predicted dramatic changes in multiple cellular activities especially downregulation of cell cycle. Comparison between two lines showed that cell cycle activity is higher in Ross than Illinois in thermoneutral condition but is decreased under heat stress. Among the significant pathways (P < 0.01) listed for different comparisons, "Mitotic Roles of Polo-like Kinases" is always ranked first.

CONCLUSIONS

The increased susceptibility of modern broilers to cardiac dysfunction under heat stress compared to slow-growing broilers could be due to diminished heart capacity related to reduction in relative heart size. The smaller relative heart size in Ross heat stress group than in Ross thermoneutral group is suggested by the transcriptome analysis to be caused by decreased cell cycle activity and increased apoptosis. The DE genes in RNA-seq analysis and significant pathways in IPA provides potential targets for breeding of heat-tolerant broilers with optimized heart function.

Maternal dietary n-3 fatty acids alter cardiac ventricle fatty acid composition, prostaglandin and thromboxane production in growing chicks

The effects of feeding n-6 and n-3 fatty acids to broiler hens on cardiac ventricle fatty acid composition, and prostaglandin E2 (PGE2) and thromboxane A2 (TXA2) production of hatched chicks were investigated. Fertile eggs obtained from hens fed diets supplemented with 3.5% sunflower oil (Low n-3), 1.75% sunflower+1.75% fish oil (Medium n-3), or 3.5% fish oil (High n-3) were incubated. The hatched chicks were fed a diet containing 18:3 n-3, but devoid of longer chain n-6 and n-3 fatty acids for 42 days. Arachidonic acid content was lower in the cardiac ventricle of High n-3 and Medium n-3 compared to Low n-3 birds for up to 2 weeks (P<0.002). Long chain n-3 fatty acids were higher in the cardiac ventricle of chicks from hens fed High and Medium n-3 diets when compared to chicks from hens fed the Low n-3 diet. Differences in long chain n-3 fatty acids persisted up to four weeks of age (P<0.001). Peripheral blood mononuclear cells (PBMNC) of 7-day-old High n-3 broilers produced significantly lower PGE2 and TXA2 than PBMNC from Low n-3 and Medium n-3 birds. These results indicate that maternal dietary n-3 fatty acids increases cardiac ventricle n-3 fatty acids while reducing arachidonic acid and ex vivo PGE2 and TXA2 production during growth in broiler chickens.

A study on pathogenesis of sudden death syndrome in broiler chickens

Sudden death syndrome (SDS) in fast growing broiler chickens has been recognized as a patho-physiological entity for four decades, but its pathogenesis still remains unknown. More recent investigations provided evidence that link SDS to cardiac arrhythmia, but the mechanism triggering arrhythmogenesis and factors responsible for fatal outcome are poorly understood. In order to understand the chain of events leading to SDS in broilers, the present study focused on putative mechanisms that trigger arrhythmia and mechanisms that predispose the myocardium to fatal arrhythmia. Susceptibility of broilers to cardiac arrhythmia under stress conditions was evaluated using a simulated stress test with epinephrine. Detailed histopathological evaluation of the broiler heart was undertaken to identify structural features that may predispose the myocardium to fatal arrhythmia. The simulated stress challenge revealed that many broilers are highly susceptible to stress induced cardiac arrhythmia. In some broilers the stress challenge induced severe ventricular arrhythmia, and the life threatening nature of this arrhythmia was evidenced by the fact that several birds showing the most severe arrhythmic responses, died suddenly within several days after the stress challenge. Examination of hearts of broilers that died of SDS revealed microscopic lesions in the cardiomyocytes, and widespread changes in the sub-endocardial and mural His-Purkinje system (HPS). Immune staining for Caspase-3 confirmed that numerous Purkinje cells in the left ventricular myocardium from broiler chickens that died of SDS were undergoing apoptosis. The observed lesions suggest that the electrical stability of the myocardium was compromised. Taken together, our findings indicate that stress is a most likely trigger of cardiac arrhythmia in broilers, whereas the pathological changes seen in the myocardium and in the HPS in fast growing broilers provide a very conducive milieu for sustained ventricular arrhythmia. In cases where the electrical stability of the myocardium is compromised, even an episodic arrhythmic event may readily degenerate to catastrophic ventricular fibrillation and sudden death. We conclude that the combination of stress and changes in the cardiomyocytes and HPS are the key requisite features in the pathogenesis of SDS.

The normal electrocardiogram of four species of conscious raptors

The aim of this study was to describe normal ECG patterns and values in four species of conscious raptors (Eurasian kestrel, Griffon vulture, Little owl, and Eurasian Eagle owl). Electrocardiograms were carried out in 75 conscious birds belonging to four species of raptors. Lead II waveforms were analysed to determine amplitudes and durations of waves and intervals. Morphologic patterns of P-QRS-T deflections were analysed in the six limb leads. Rhythm, heart rate, mean electrical axis, presence of Ta wave, ST slurring, and P-on-T phenomenon were also studied. The influence of species, body weight and heart rate in electrocardiographic variables were statistically analysed (P < 0.05). Sinus rhythm was present in all tracings, showing sinus arrhythmia in four cases. Ta wave was present in six tracings and P-on-T phenomenon in four. ST segment could be identified in all tracings, being mainly high above baseline. Significant differences between species were found for all the electrocardiographic parameters. The heart rate and body weight were also found to be a significant influence in most parameters. This study provides electrocardiographic data for four species of raptors that can be used to establish comparisons for clinical purposes.

Biochemical factors limiting myocardial energy in a chicken genotype selected for rapid growth

Broiler chickens (Gallus gallus) genetically selected for rapid growth are inherently predisposed to heart failure. In order to understand the biochemical mechanisms associated with the deterioration of heart function and development of congestive heart failure (CHF) in fast-growing chickens, this study examined several factors critical for myocardial energy metabolism. Measured variables included cardiac energy substrates [creatine phosphate (CrP), adenosine triphosphate (ATP), l-carnitine], activity of selected cytosolic enzymes [creatine kinase (CK; EC 2.7.3.2), lactate dehydrogenase (LDH; EC 1.1.1.27)] and mitochondrial enzymes [pyruvate dehydrogenase (PDH; EC 1.2.4.1), alpha-ketoglutarate dehydrogenase (alpha-KGDH; EC 1.2.4.2)]. The CK activities were higher in fast-growing and CHF broilers as compared to slow-growing broilers (p<0.05). Cardiac LDH and alpha-KGDH activities were not changed (p>0.05), whereas PDH activity was highest (p<0.05) in broilers with CHF. Deterioration of heart function is correlated with lowered cardiac ATP, CrP, and l-carnitine levels (all p<0.05). Depletion of high energy phosphate substrates, ATP and CrP, is evident in fast-growing chickens and those that developed CHF. Increased activity of CK suggests that cardiac energy management in fast-growing broilers and those with CHF largely depends on contribution of this pathway to regeneration of ATP from CrP. In this scenario, inadequate level of CrP is a direct cause of ATP insufficiency, whereas low cardiac l-carnitine, because of its role in fatty acid transport, is most likely an important factor contributing to shortage of key substrate required for synthesis of cardiac ATP. The insufficiencies in cardiac energy substrate synthesis provide metabolic basis of myocardial dysfunction in chickens predisposed to heart failure.

Pathophysiology of heart failure in broiler chickens: structural, biochemical, and molecular characteristics

Modern strains of fast-growing meat type poultry are highly susceptible to heart failure. Heart-related mortalities are observed predominantly in fast-growing broiler chickens, with ascites and sudden death syndrome being the most common heart-related conditions in modern broiler flocks. This paper examines the role of structural, molecular, and biochemical factors pertinent to the pathophysiology of heart failure in fast-growing broilers. Evidence explaining the pathogenesis of acute and chronic heart failure, in the context of the underlying molecular and biochemical changes in the cardiomyocytes, contractile apparatus, and extracellular matrix in the ventricular myocardium are critically evaluated and discussed with reference to the clinical signs associated with deterioration of heart pump function. The secondary pathophysiological effects on the cardiovascular system, resulting from hemodynamic changes associated with the failing heart pump, are also reviewed and critically discussed.

Maternal dietary n-3 fatty acids alter immune cell fatty acid composition and leukotriene production in growing chicks

The effect of feeding different amounts of n-6 and n-3 fatty acids (FA) to hens on immune tissue FA composition and leukotriene production of hatched chicks was investigated. Hens were fed diets supplemented with either 3.0% sunflower oil (Diet I), 1.5% sunflower+1.5% fish oil (Diet II), or 3.0% fish oil (Diet III) for 46 days. The hatched chicks were fed a diet containing C18:3n-3, but devoid of longer chain n-6 and n-3 FA, for 21 days. Spleen docosahexaenoic acid (DHA) content was higher in chicks from hens fed Diet III (P<0.05). The bursa content of arachidonic acid was lower in chicks hatched from hens fed Diet III (P<0.05), and the ratio of n-6 to n-3 FA was significantly higher in bursa of chicks hatched to hens fed Diet I (P<0.05). Eicosapentaenoic acid (EPA) and DHA contents were higher in bursa of chicks hatched from hens fed Diet III (P<0.05). Thrombocytes from chicks hatched to hens fed Diet III produced the most leukotriene B(5) (LTB(5)). The ratio of LTB(5) to LTB(4) concentrations was also highest (P<0.05) in chicks hatched to hens fed Diet III. These results indicate that modulating maternal dietary n-6 and n-3 FA may alter leukotriene production in chicks, which could lead to less inflammatory-related disorders in poultry.

Left ventricular myocardal activation under ventricular paced beats in chickens Gallus gallus domesticus

The aim of the study was to advance our knowledge regarding the activation process of the ventricular myocardium in birds in which Purkinje fibres penetrate into the ventricular wall to reach the epicardium. A depolarization pattern of the left ventricular free wall was studied in chickens (Gallus gallus) during ventricular paced beats. Duration of the activation process of the left ventricular free wall is significantly increased during ventricular ectopic excitation as compared with sinus rhythm. Its lowest increase occurs during subendocardial pacing of the middle part of the left ventricle, but its greatest increase is observed during subepicardial pacing of the left ventricular base. Multifocality and mosaicity of depolarization of the left ventricular free wall myocardium in chicken are expressed in a considerably less degree during ventricular paced beats in comparison with sinus rhythm. During ventricular paced beats, excitation of the left ventricular free wall is mostly due to the successive spreading of the depolarization wave from pacing sites.

The role of sodium ions in the pathogenesis of skeletal muscle damage in broiler chickens

The effect of sodium ions (Na+) on calcium (Ca2+)-mediated muscle damage in broiler chickens was investigated using an in vitro muscle preparation. Muscle Ca2+ accumulation was determined by 45Ca2+ uptake. Muscle damage was assessed by measurement of the efflux of the intracellular enzyme creatine kinase (CK) into the incubation medium. Loading muscle cells with Na+ by means of the sodium ionophore monensin led to concentration-dependent (25 to 200 microM) increases in 45Ca2+ uptakes and corresponding and proportional CK losses. The greatest responses occurred at 100 microM ionophore or greater, reflected in a 49% increase (P < 0.05) in 45Ca2+ uptake and an associated 140%-fold increase (P < 0.001) in CK efflux. Inhibition of muscle Na+/K+-ATPase activity with ouabain (2 mM) induced a 56% increase in 45Ca2+ uptake and a 60%-fold increase (P < 0.001) in total CK loss. The combined use of ionophore and ouabain resulted in 90 and 130%-fold elevations in 45Ca2+ uptake and CK loss, respectively. In monensin-treated muscles, inhibition of external Ca2+ influx from the incubation medium by chelation with 1,2 bis(2-aminophenoxy)ethane-N,N,N',N' tetracetic acid (5 mM) markedly reduced 45Ca2+ uptake (38%: P < 0.05) but increased CK release by 85% (P < 0.001). The results demonstrate that initial elevations in muscle Na+ can facilitate increases in muscle Ca2+ and lead to alterations in muscle cell membrane integrity and CK loss. The Na+-induced increases in myocellular Ca2+ may be mediated via direct extracellular Ca2+ entry or redistribution from internal Ca2+ stores. It is proposed that in order to reduce or prevent myopathies in poultry, exposure to conditions that may lead to elevations in muscle Na+ (e.g., increased muscle activity and stress or accidental ionophore toxicosis) should be avoided. The findings of this study have implications for management strategies of bird welfare, muscle pathology, and product quality.

Lesions of the pericardium and their significance in the aetiology of heart failure in broiler chickens

The present study focuses on lesions of the pericardium commonly observed in fast growing broilers. These lesions are examined in the context of electrophysiological and functional changes associated with cardiac performance and patho-physiology in broilers succumbing to acute or chronic heart failure. Typical lesions involving the pericardium in fast growing broiler chickens included: (1) excessive pericardial effusion, (2) locally extensive or focal adhesions between parietal and visceral components of the pericardium, (3) fibrous deposits on visceral pericardium, and (4) thickened pericardium. Echocardiographic evidence indicated that severe pericardial effusion and/or adhesions may have a restrictive effect on heart pump function, where both diastolic and systolic function of the heart may be affected. Electrocardiographic data showed a strong trend indicating that pericardial adhesions may be associated with ventricular arrhythmia and increased risk of sudden death in fast growing broilers. Relatively high levels of matrix metalloproteinase MMP-2 activity have been found in pericardial effusions from affected chickens, suggesting a possible involvement of this enzyme in the aetiology of pericardial lesions. The present results indicate that pericardial lesions may be associated with biochemical, morphological, electrophysiological, and functional changes occurring in the hearts of broilers succumbing to acute or chronic heart failure and ascites.

The effects of toasting canola meal on body weight, feed conversion efficiency, and mortality in broiler chickens

It is hypothesized that the moisture incorporated into canola meal (CM) during desolventization, as sparge steam, promotes toasting. Elimination of toasting of CM would result in higher digestible amino acid content, but it is not known if it is required to reduce anti-nutritional factors. Therefore, the objectives of this study were to determine if suspending the use of sparge steam would prevent toasting and to study the effects of toasting on broiler chicken performance. Conventional toasted CM (TCM) and a hexane laden, nontoasted CM (NTCM) were collected from a commercial crushing plant. NTCM was desolventized in a research desolventizer/toaster without the use of sparge steam, producing a yellow-colored meal. The meals were fed to broiler chickens from 0 to 39 d and replaced 0, 20, 40, 60, 80, and 100% of the soybean meal (SBM) in wheat-based diets. Elimination of toasting increased broiler weight from 0.606 and 2.148 to 0.618 and 2.181 kg at 19 and 39 d of age, respectively. The feed ratio (0 to 19 d) increased from 0.637 to 0.642, but toasting did not affect mortality. Total mortality and chronic heart failure between 19 and 39 d increased with level of CM addition from 5.2 to 13.9% and 1.9 to 9.6%, respectively. Chronic heart failure in males, but not females, was increased from 3.3 to 17.4% with increasing CM level. In conclusion, desolventization without sparge steam produced a nontoasted meal and improved broiler growth and feed efficiency in comparison to TCM. Therefore, NTCM could be fed to broiler chickens.

Ultrastructural and molecular changes in the left and right ventricular myocardium associated with ascites syndrome in broiler chickens raised at low altitude

The present study examines ultrastructural and molecular changes in ventricular myocardium associated with ascites cases in fast-growing broilers raised at low altitude. Extensive ultrastructural lesions were seen in the left and right ventricular myocardium of broilers with fulminant heart failure and ascites. Significant changes included lesions in the myofibril contractile apparatus, altered mitochondria, marked reduction in the myofibril component, and changes in the extracellular matrix (ECM) architecture. No lesions were observed in hearts of slow growing broilers, but mild to moderate changes (predominantly in the left ventriculum) were apparent in the hearts from some clinically normal, fast-growing broilers. SDS-PAGE profiles of washed myofibrils showed several distinctly different bands in preparations from left ventricular myocardium of ascitic birds. Western blot analysis of these samples revealed several fragments of myosin heavy chain, M-protein, and titin. Based on gelatinolytic activity, matrix metalloproteinases (MMP) in the cytosolic fraction of ventricular myocardium homogenates were identified as MMP-2. The relative activity of this enzyme appears to be considerably higher in preparations from broilers, particularly in the preparations from the left ventriculum of fast-growing broilers, in comparison to leghorns or slow growing broilers. The nature and distribution of the changes in the heart indicate that chronic cardiomyopathic process in the left ventricular myocardium occurs during the development of ascites. It is postulated that progressive deterioration of the left heart pump function caused by initial lesions in the left ventricular myocardium is a significant factor in the development of pulmonary hypertension and the pathogenesis of ascites in broilers raised at low altitude.

High carbon dioxide tension (PCO2) and the incidence of cardiac arrhythmias in rapidly growing broiler chickens

The purpose of this investigation was to determine whether two-week-old rapidly growing broiler chickens with high metabolic activity have an increased risk of the development of heart failure three to five weeks later. The incidence of cardiac arrhythmias was assessed in broiler chickens with either a relatively high carbon dioxide tension (PCO2) or a low PCO2 in their venous blood. Their electrocardiograms (ECGS) were measured when the birds were between five and seven weeks old by means of a biotransplant which allowed them to move freely. Premature ventricular beats were observed in all the birds, but the largest numbers were observed in birds that had had a high PCO2 when they were two weeks old.