Taurine, cardiopulmonary hemodynamics, and pulmonary hypertension syndrome in broilers

Taurine mitigates the development of pulmonary inflammation, oxidative stress, and histopathological alterations in a rat model of bile duct ligation

Lung injury is a significant complication associated with cholestasis/cirrhosis. This problem significantly increases the risk of cirrhosis-related morbidity and mortality. Hence, finding effective therapeutic options in this field has significant clinical value. Severe inflammation and oxidative stress are involved in the mechanism of cirrhosis-induced lung injury. Taurine (TAU) is an abundant amino acid with substantial anti-inflammatory and antioxidative properties. The current study was designed to evaluate the role of TAU in cholestasis-related lung injury. For this purpose, bile duct ligated (BDL) rats were treated with TAU (0.5 and 1% w: v in drinking water). Significant increases in the broncho-alveolar lavage fluid (BALF) level of inflammatory cells (lymphocytes, neutrophils, basophils, monocytes, and eosinophils), increased IgG, and TNF-α were detected in the BDL animals (14 and 28 days after the BDL surgery). Alveolar congestion, hemorrhage, and fibrosis were the dominant pulmonary histopathological changes in the BDL group. Significant increases in the pulmonary tissue biomarkers of oxidative stress, including reactive oxygen species formation, lipid peroxidation, increased oxidized glutathione levels, and decreased reduced glutathione, were also detected in the BDL rats. Moreover, significant myeloperoxidase activity and nitric oxide levels were seen in the lung of BDL rats. It was found that TAU significantly blunted inflammation, alleviated oxidative stress, and mitigated lung histopathological changes in BDL animals. These data suggest TAU as a potential protective agent against cholestasis/cirrhosis-related lung injury.

NaHCO3, L-arginine, and vitamin C supplemented vegetable diet ameliorates tachycardia and polycythemia in the broiler chicken

The study aimed to investigate if vegetable-based high-energy mash diets supplemented with NaHCO₃, L-arginine + vitamin C, and vegetable oils were effective against tachycardia and polycythemia in the broiler chicken. A total of 256 Ross-308 day-old male broiler chicks were randomly distributed into eight dietary treatment groups in a three-way ANOVA with 2 × 2 × 2 factorial arrangement (three factors, i.e., NaHCO₃, L-arginine + vitamin C, and vegetable oil each with two levels, e.g., 0 and 0.1% of NaHCO₃ and L-arginine + vitamin C; 3 and 4% of vegetable oil supplemented with basal diet) for a period of 35 days. Iso-caloric and iso-nitrogenous diets were formulated and supplied ad libitum. The final live weight (FLW), average daily feed intake (ADFI), average daily gain (ADG), feed efficiency (FE), carcass traits, cardio-pulmonary morphometry, total protein (TP), hemoglobin (Hb), triiodothyronine (T₃), incidence of tachycardia, and polycythemia were examined. Supplementation of NaHCO₃ increased 2.2% ADFI, 5.5% FE, and 23.2% TP. The L-arginine + vitamin C increased 2.4% FLW and decreased 1.9% heart rate. Vegetable oil increased 1.3% ADFI, 4.2% ADG, 8.6% FE, 23.1% Hb, and 15.5% PCV. The NaHCO₃, L-arginine + vitamin C, and vegetable oil additively interacted to increase 31.5% T₃ at the expense of 21.1% of the weight of the right ventricle (RV). The RV:TV, carcass traits, and hemato-biochemical indices remained within normal range irrespective of the levels of the supplementations of the test ingredients. It was concluded that vegetable-based high-energy mash diets were not susceptible to tachycardia and polycythemia. The addition of NaHCO₃ and L-arginine + vitamin C ameliorated the propensity of tachycardia and polycythemia without deteriorating performance, carcass traits, and hemato-biochemical indices of the broiler chicken in a dose-dependent manner.

Further investigation of a quantitative trait locus for ascites on chromosome 9 in broiler chicken lines

Previously, we reported a genome wide association study (GWAS) that had shown association of a region between 11.8 and 13.6 Mbp on chromosome 9 with ascites phenotype in broilers. We had used microsatellite loci to demonstrate an association of particular genotypes for this region with ascites in experimental ascites lines and commercial broiler breeder lines. We identified two potential candidate genes, AGTR1 and UTS2D, within that chromosomal region for mediating the quantitative effect. We have now extended our analysis using SNPs for these genes to assess association with resistance or susceptibility to ascites in these same broiler lines. Surprisingly, in contrast to our previous GWAS and microsatellite data for this region, we find no association of the SNP genotypes or haplotypes in the region suggesting that the two genes might have limited association with the disease phenotype.

Multi-generational genome wide association studies identify chromosomal regions associated with ascites phenotype

Ascites is a multi-faceted disease commonly observed in fast growing broilers, which is initiated when the body is insufficiently oxygenated. A series of events follow, including an increase in pulmonary artery pressure, right ventricle hypertrophy, and accumulation of fluid in the abdominal cavity and pericardium. Advances in management practices along with improved selection programs have decreased ascites incidence in modern broilers. However, ascites syndrome remains an economically important disease throughout the world, causing estimated losses of $100 million per year. In this study, a 60 K Illumina SNP BeadChip was used to perform a series of genome wide association studies (GWAS) on the 16th and 18th generation of our relaxed (REL) line descended from a commercial elite broiler line beginning in 1995. Regions significantly associated with ascites incidence were identified on chromosome 2 around 70 megabase pairs (Mbp) and on chromosome Z around 60 Mbp. Five candidate single nucleotide polymorphisms (SNP) were evaluated as indicators for these 2 regions in order to identify association with ascites and right ventricle to total ventricle weight (RVTV) ratios. Chromosome 2 SNP showed an association with RVTV ratios in males phenotyped as ascites resistant and ascites susceptible (P = 0.02 and P = 0.03, respectively). The chromosome Z region also indicates an association with resistant female RVTV values (P = 0.02). Regions of significance identified on chromosomes 2 and Z described in this study will be used as proposed candidate regions for further investigation into the genetics of ascites. This information will lead to a better understanding of the underlying genetics and gene networks contributing to ascites, and thus advances in ascites reduction through commercial breeding schemes.

Effects of Rhodiola on production, health and gut development of broilers reared at high altitude in Tibet

Rhodiola has long been used as a traditional medicine to increase resistance to physical stress in humans in Tibet. The current study was designed to investigate whether Rhodiola crenulata (R. crenulata) could alleviate the negative effects of hypoxia on broiler chickens reared in Tibet Plateau. The effect of supplementing crushed roots of R. crenulata on production performance, health and intestinal morphology in commercial male broilers was investigated. Dietary treatments included CTL (basal diet), Low-R (basal diet + 0.5% R. crenulata) and High-R (basal diet + 1.5% R. crenulata). In comparison with broilers fed the control diet, Low-R had no effect on production performance while High-R significantly decreased average daily feed intake at d 14, 28 and 42, body weight at d 28 and 42 and gut development. Ascites induced mortality did not differ among treatments. Nevertheless Low-R significantly reduced non-ascites induced mortality and total mortality compared with broilers fed CTL and High-R diets. Broilers fed the High-R diet had significantly increased blood red blood cell counts and hemoglobin levels at 28 d compared with other treatments. Our results suggest that supplementation with Rhodiola might reduce the effects of hypoxia on broilers and consequently decrease mortality rate.

Pulmonary arterial hypertension (ascites syndrome) in broilers: a review

Pulmonary arterial hypertension (PAH) syndrome in broilers (also known as ascites syndrome and pulmonary hypertension syndrome) can be attributed to imbalances between cardiac output and the anatomical capacity of the pulmonary vasculature to accommodate ever-increasing rates of blood flow, as well as to an inappropriately elevated tone (degree of constriction) maintained by the pulmonary arterioles. Comparisons of PAH-susceptible and PAH-resistant broilers do not consistently reveal differences in cardiac output, but PAH-susceptible broilers consistently have higher pulmonary arterial pressures and pulmonary vascular resistances compared with PAH-resistant broilers. Efforts clarify the causes of excessive pulmonary vascular resistance have focused on evaluating the roles of chemical mediators of vasoconstriction and vasodilation, as well as on pathological (structural) changes occurring within the pulmonary arterioles (e.g., vascular remodeling and pathology) during the pathogenesis of PAH. The objectives of this review are to (1) summarize the pathophysiological progression initiated by the onset of pulmonary hypertension and culminating in terminal ascites; (2) review recent information regarding the factors contributing to excessively elevated resistance to blood flow through the lungs; (3) assess the role of the immune system during the pathogenesis of PAH; and (4) present new insights into the genetic basis of PAH. The cumulative evidence attributes the elevated pulmonary vascular resistance in PAH-susceptible broilers to an anatomically inadequate pulmonary vascular capacity, to excessive vascular tone reflecting the dominance of pulmonary vasoconstrictors over vasodilators, and to vascular pathology elicited by excessive hemodynamic stress. Emerging evidence also demonstrates that the pathogenesis of PAH includes characteristics of an inflammatory/autoimmune disease involving multifactorial genetic, environmental, and immune system components. Pulmonary arterial hypertension susceptibility appears to be multigenic and may be manifested in aberrant stress sensitivity, function, and regulation of pulmonary vascular tissue components, as well as aberrant activities of innate and adaptive immune system components. Major genetic influences and high heritabilities for PAH susceptibility have been demonstrated by numerous investigators. Selection pressures rigorously focused to challenge the pulmonary vascular capacity readily expose the genetic basis for spontaneous PAH in broilers. Chromosomal mapping continues to identify regions associated with ascites susceptibility, and candidate genes have been identified. Ongoing immunological and genomic investigations are likely to continue generating important new knowledge regarding the fundamental biological bases for the PAH/ascites syndrome.

Myocardial contractility in chickens (Gallus gallus): Analysis of systolic time intervals

The avian cardiovascular system is of special interest because avian hearts are relatively larger than mammalian hearts, and activation of ventricular myocardium in birds has a "flash" pattern. Systolic time intervals and indices of myocardial contractility were examined in anaesthetized open-chest chickens by polycardiography, including synchronous recordings of electrocardiogram, phonocardiogram, and apex cardiogram. The asynchronous contraction time, isometric contraction time, pre-ejection period and ejection time were 26 +/- 3 (Mean +/- SD), 21 +/- 9, 47 +/- 12, and 83 +/- 23 ms, respectively, for heart rates of 260 +/- 57 bpm. The myocardial tension index, isometric contraction index and the pre-ejection period/ejection time ratio were 0.39 +/- 0.11, 0.42 +/- 0.10, and 0.54 +/- 0.14, respectively. A "flash" pattern of ventricular myocardial depolarization causes more rapid excitation and as a consequence shorter asynchronous contraction time of relatively larger chicken hearts compared with rabbit hearts. Inverse relation (P < 0.05) of the asynchronous contraction time to the heart rate in chickens is probably associated with the specific activation pattern of avian ventricles. Establishment of the values of systolic time intervals will facilitate a better understanding of cardiac function in birds. The obtained results are discussed in comparison with the rabbit. The indices calculated from the systolic time intervals show disadvantageous contractile function of chicken heart compared to rabbit heart.

Nω-nitro-L-arginine methyl ester (L-NAME) amplifies the pulmonary hypertensive response to microparticle injections in broilers

We tested the hypothesis that microparticles entrapped within the pulmonary vasculature elicit the production of nitric oxide (NO) in quantities sufficient to modulate the combined impact of physical occlusion plus contemporaneously released vasoconstrictors. In experiment 1, male broilers were given an injection of the NO synthase (NOS) inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME), followed by an intravenous injection of cellulose microparticles while the pulmonary arterial pressure (PAP) and cardiac output (CO) were recorded. When L-NAME was used to block NO synthesis induced by the microparticles, an early peak of pulmonary hypertension was revealed that rarely developed in the absence of L-NAME. The subsequent more prolonged increases in PAP and pulmonary vascular resistance (PVR) were greater in amplitude and duration in broilers pretreated with L-NAME than in broilers in the control group. These amplified responses occurred in spite of a simultaneous reduction in CO, thereby conclusively demonstrating that inhibiting NOS permitted the development of a much more profound increase in the PVR. In experiment 2 the mortality triggered within 48 h after injecting microparticles was evaluated in the presence and absence of L-NAME. The 48 h postinjection mortality more than doubled when L-NAME was combined with microparticle injection doses that otherwise caused relatively low mortality in the absence of L-NAME. Experiment 3 was conducted to determine whether NO contributes to the systemic hypoxemia that develops after microparticles are injected. L-NAME administration had no impact on the magnitude and duration of the microparticle induced decline in the percentage saturation of hemoglobin with oxygen (%HbO2). Evidently hypoxemia per se contributes relatively little to the amplified pulmonary vasoconstriction and 48 h postinjection mortality triggered by microparticle injections in broilers pretreated with L-NAME. These observations indicate that NO modulates the responses to vasoconstrictors released when microparticles become entrapped in the pulmonary vasculature. Inhibition of NOS by L-NAME exposed a more dramatic increase in PVR and pulmonary hypertension leading to enhanced mortality in response to microparticle injections.

Dietary sodium bicarbonate, cool temperatures, and feed withdrawal: impact on arterial and venous blood-gas values in broilers

Sodium bicarbonate (NaHCO3) has been used successfully in mammals and birds to alleviate pulmonary hypertension. Experiment 1 was designed to provide measurements of arterial and venous blood-gas values from unanesthetized male broilers subjected to a cool temperature (16 degrees C) challenge and fed either a control diet or the same diet alkalinized by dilution with 1% NaHCO3. The incidences of pulmonary hypertension syndrome (PHS, ascites) for broilers fed the control or bicarbonate diets were 15.5 and 10.5%, respectively (P = 0.36, NS). Non-ascitic broilers fed the control diet were heavier than those fed the bicarbonate diet on d 49 (2,671 vs. 2,484 g, respectively); however, other comparisons failed to reveal diet-related differences in heart weight, pulse oximetry values, electrocardiogram amplitudes, or blood-gas values (P > 0.05). When the data were resorted into categories based on right:total ventricular weight ratios (RV:TV) indicative of normal (RV:TV < 0.28) or elevated (RV:TV > or = 0.28) pulmonary arterial pressures, broilers with elevated RV:TV ratios had poorly oxygenated arterial blood that was more acidic, had high partial pressure of CO2 (PCO2), and had higher HCO3 concentrations when compared with broilers with normal RV:TV ratios. Experiment 2 was conducted to determine if metabolic variations associated with differences in feed intake or environmental temperature potentially could mask an impact of diet composition on blood-gas values. Male broilers maintained at thermoneutral temperature (24 degrees C) either received feed ad libitum or had the feed withdrawn > or = 12 h prior to blood sampling. Broilers fed ad libitum had lower venous saturation of hemoglobin with O2, higher venous PCO2, and higher arterial HCO3 concentrations than broilers subjected to feed withdrawal. Broilers in experiment 2 fed ad libitum and exposed to cool temperatures (16 degrees C) had lower arterial partial pressure of O2 and higher venous PCO2 than broilers fed ad libitum and maintained at 24 degrees C. Overall, these results demonstrate that changes in diet composition (control vs. 1% NaHCO3 diets) had minimal impact on arterial and venous blood-gas variables when compared with the more dramatic differences associated with feed intake (ad libitum vs. > or = 12 h withdrawal), environmental temperature (24 vs. 16 degrees C), and the pathogenesis associated with PHS (RV:TV < 0.28 vs. > or = 0.28).