Ascites in poultry: Recent investigations

A critical assessment of the cellular defences of the avian respiratory system: are birds in general and poultry in particular relatively more susceptible to pulmonary infections/afflictions?

In commercial poultry farming, respiratory diseases cause high morbidities and mortalities, begetting colossal economic losses. Without empirical evidence, early observations led to the supposition that birds in general, and poultry in particular, have weak innate and adaptive pulmonary defences and are therefore highly susceptible to injury by pathogens. Recent findings have, however, shown that birds possess notably efficient pulmonary defences that include: (i) a structurally complex three-tiered airway arrangement with aerodynamically intricate air-flow dynamics that provide efficient filtration of inhaled air; (ii) a specialised airway mucosal lining that comprises air-filtering (ciliated) cells and various resident phagocytic cells such as surface and tissue macrophages, dendritic cells and lymphocytes; (iii) an exceptionally efficient mucociliary escalator system that efficiently removes trapped foreign agents; (iv) phagocytotic atrial and infundibular epithelial cells; (v) phagocytically competent surface macrophages that destroy pathogens and injurious particulates; (vi) pulmonary intravascular macrophages that protect the lung from the vascular side; and (vii) proficiently phagocytic pulmonary extravasated erythrocytes. Additionally, the avian respiratory system rapidly translocates phagocytic cells onto the respiratory surface, ostensibly from the subepithelial space and the circulatory system: the mobilised cells complement the surface macrophages in destroying foreign agents. Further studies are needed to determine whether the posited weak defence of the avian respiratory system is a global avian feature or is exclusive to poultry. This review argues that any inadequacies of pulmonary defences in poultry may have derived from exacting genetic manipulation(s) for traits such as rapid weight gain from efficient conversion of food into meat and eggs and the harsh environmental conditions and severe husbandry operations in modern poultry farming. To reduce pulmonary diseases and their severity, greater effort must be directed at establishment of optimal poultry housing conditions and use of more humane husbandry practices.

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.

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.

Effects of incubator oxygen and carbon dioxide concentrations on hatchability of fertile eggs, some blood parameters, and histopathological changes of broilers with different parental stock ages in high altitude

The effects of incubator carbon dioxide (CO₂) and oxygen (O₂) concentrations with parental stock age (PSA) on embryonic deaths (ED), hatchability of fertile eggs (HFE), some blood parameters, and the tissue development of broilers were investigated. Four consecutive repetitions following the similar materials and methods were carried. From 3 different aged ROSS 308 broiler parental flocks 7,680 hatching eggs were obtained and classified as young (Y; 29 wk), middle (M; 37 wk) and old (O; 55 wk) as regards PSA, and randomly distributed. Four different incubator ventilation programs (IVP) as control (C; 0.67% CO₂ and 20.33% O₂), high CO₂ (HC; 1.57% CO₂ and 20.26% O₂), high O₂ (HO; 0.50% CO₂ and 21.16% O₂), and high CO₂ + O₂ (HCO; 1.17% CO₂ 21.03% O₂) were applied with oxygen concentrator, and ED and HFE were investigated. Lung and heart tissues, hemoglobin value, packed cell volume, and red blood cell count, triiodothyronine, thyroxine, adrenocorticotropic hormone (ACTH) values of the chicks were analyzed. It was found that IVP affected ED and HFE. Higher rate of early ED (EED) was obtained from the HC than HCO, and higher middle+late stage+pipped but unhatched ED (MLPED) with a lower rate of HFE was observed in the C group than HO and HCO (P < 0.05). Association was found between PSA and IVP (P < 0.05), being more evident in EED for young PSA, in MLPED with HFE for Y and O PSA. From hematological values, no statistical difference in RBC, PCV, and Hb values were found among the treatment groups, ACTH concentration known as a response to stress was found to be higher than C in all groups, triiodothyronine concentration was higher in the HO group than C. In the histopathological examination, used IVPs were found to have negative effects on the lung and heart such as vacuolization, hemorrhage in all PSA groups except for C. Conclusively, PSA and IVP affected some hatching, blood and tissue development parameters of the broiler chicks.

Further investigation of mitochondrial biogenesis and gene expression of key regulators in ascites- susceptible and ascites- resistant broiler research lines

We have extended our previous survey of the association of mitochondrial prevalence in particular tissues with ascites susceptibility in broilers. We previously reported that in breast muscle of 22 week old susceptible line male birds had significantly higher mtDNA copy number relative to nuclear copy number (mtDNA/nucDNA), compared to resistant line male birds. The higher copy number correlated with higher expression of PPARGC1A mRNA gene. Ascites is a significant metabolic disease associated with fast-growing meat-type chickens (broilers) and is a terminal result of pulmonary hypertension syndrome. We now report the mtDNA/nucDNA ratio in lung, liver, heart, thigh, and breast of both genders at 3, and 20 weeks old. At 3 weeks the mtDNA/nucDNA ratio is significantly higher in lung, breast, and thigh for susceptible line males compared to the resistant line males. Conversely, we see the opposite for lung and breast in females. At 20 weeks of age the differences between males from the two lines is lost for lung, and thigh. Although there is a significant reduction in the mtDNA/nucDNA ratio of breast from 3 weeks to 20 weeks in the susceptible line males, the susceptible males remain higher than resistant line males for this specific tissue. We assessed relative expression of five genes known to regulate mitochondrial biogenesis for lung, thigh and breast muscle from males and females of both lines with no consistent pattern to explain the marked gender and line differences for these tissues. Our results indicate clear sex differences in mitochondrial biogenesis establishing a strong association between the mtDNA quantity in a tissue-specific manner and correlated with ascites-phenotype. We propose that mtDNA/nucDNA levels could serve as a potential predictive marker in breeding programs to reduce ascites.

Total Mercury Determination in Muscle and Liver Tissue Samples from Brazilian Amazon Fish Using Slurry Sampling

This paper presents a slurry sampling method for total mercury determination by graphite furnace atomic absorption spectrometry (GFAAS) in tissue of fish from the Amazon. The tissue samples were lyophilized and macerated, and then the slurry samples were prepared by putting 20 mg of tissue, added to a solution containing Triton X-100, Suprapur HNO₃, and zirconium nitrate directly in sampling vials of a spectrometer. Mercury standard solutions were prepared under the same conditions as the slurry samples. The slurry samples and the mercury standard solutions were sonicated for 20 s. Twenty microliters of slurry samples were injected into the graphite tube, which contained an internal wall lined with tungsten carbide. Under these conditions, it was possible to thermally stabilize the mercury up to an atomization temperature of 1700 °C. The method was validated by mercury determination in reference materials DORM-4 and DOLT-4. The LOD and LOQ were 0.014 and 0.045 mg kg^-1, respectively, and recovery percentages in relation to the concentration values were certified in the order of 98%.

Combinatory Evaluation of Transcriptome and Metabolome Profiles of Low Temperature-induced Resistant Ascites Syndrome in Broiler Chickens

To select metabolic biomarkers and differentially expressed genes (DEGs) associated with resistant-ascites syndrome (resistant-AS), we used innovative techniques such as metabolomics and transcriptomics to comparatively examine resistant-AS chickens and AS controls. Metabolomic evaluation of chicken serum using ultra-performance liquid chromatography-quadruple time-of-flight high-sensitivity mass spectrometry (UPLC-QTOF/HSMS) showed significantly altered lysoPC(18:1), PE(18:3/16:0), PC(20:1/18:3), DG(24:1/22:6/0:0), PS(18:2/18:0), PI(16:0/16:0), PS(18:0/18:1), PS(14:1/14:0), dihydroxyacetone, ursodeoxycholic acid, tryptophan, L-valine, cycloserine, hypoxanthine, and 4-O-Methylmelleolide concentrations on day 21 and LysoPC(18:0), LysoPE(20:1/0:0), LysoPC(16:0), LysoPE(16:0/0:0), hypoxanthine, dihydroxyacetone, 4-O-Methylmelleolide, LysoPC(18:2), and PC(14:1/22:1) concentrations on day 35, between the susceptible and resistant groups. Compared to the susceptible group, transcriptomic analysis of liver samples using RNA-seq revealed 413 DEGs on day 21 and 214 DEGs on day 35 in the resistant group. Additional evaluations using gene ontology (GO) indicate that significant enrichment occurred in the oxygen transportation, defensive reactions, and protein modifications of the decreased DEGs as well as in the cell morphological formation, neural development, and transforming growth factor (TGF)-beta signalling of the increased DEGs on day 21. Oxygen transportation was also significantly enriched for downregulated DEGs on day 35. The combinatory evaluation of the metabolome and the transcriptome suggests the possible involvement of glycerophospholipid metabolism in the development of resistant-AS in broilers.

Protective roles of free avian respiratory macrophages in captive birds

In the mammalian lung, respiratory macrophages provide front line defense against invading pathogens and particulate matter. In birds, respiratory macrophages are known as free avian respiratory macrophages (FARM) and a dearth of the cells in the avian lung has been purported to foreordain a weak first line of pulmonary defense, a condition associated with high mortality of domestic birds occasioned by respiratory inflictions. Avian pulmonary mechanisms including a three tiered aerodynamic filtration system, tight epithelial junctions and an efficient mucociliary escalator system have been known to supplement FARM protective roles. Current studies, however, report FARM to exhibit an exceptionally efficient phagocytic capacity and are effective in elimination of invading pathogens. In this review, we also report on effects of selective synthetic peroxisome proliferator activated receptor gamma (PPAR γ) agonists on non phlogistic phagocytic properties in the FARM. To develop effective therapeutic interventions targeting FARM in treatment and management of respiratory disease conditions in the poultry, further studies are required to fully understand the role of FARM in innate and adaptive immune responses.

Activation of peroxisome proliferator-activated receptor gamma induces anti-inflammatory properties in the chicken free avian respiratory macrophages

Background

Activation of peroxisome proliferator activated receptor gamma (PPAR γ) in the alveolar macrophages (AM) by selective synthetic PPAR γ ligands, improves the ability of the cells to resolve inflammation. In birds, respiratory macrophages are known as free avian respiratory macrophages (FARM) and show distinct functional differences from AM. The effects of treating FARM with PPAR γ ligands are unclear.

Methods

FARM were harvested by lavage of chicken respiratory tract and their morphology assessed at microscopic level. The effects of PPAR γ agonists on the FARM in vitro viability, phagocytic capacity and proinflammatory cytokine (TNF-α) production were assessed.

Results

FARM had eccentric nucleus and plasma membrane ruffled with filopodial extensions. Ultrastructurally, numerous vesicular bodies presumed to be lysosomes were present. FARM treated with troglitazone, a selective PPAR γ agonist, had similar in vitro viability with untreated FARM. However, treated FARM co-cultured with polystyrene particles, internalized more particles with a mean volume density of 41 % compared to that of untreated FARM of 21 %. Further, treated FARM significantly decreased LPS-induced TNF-α production in a dose dependent manner.

Conclusion

Results from this study show that PPAR γ synthetic ligands enhance phagocytic ability of FARM. Further the ligands attenuate production of proinflammatory cytokines in the FARM, suggesting potential therapeutic application of PPAR γ ligands in the management of respiratory inflammatory disorders in the poultry industry.

Effect of Origanum chemotypes on broiler intestinal bacteria

Essential oils have been proposed as alternatives to antibiotic use in food animal production. This study evaluated 3 chemotypes of the Origanum genus, containing varying amounts of secondary metabolites carvacrol, thymol, and sabinene, in the broiler chicken diet. Aerial parts of Origanum vulgare L. (OL), O. vulgare L. ssp. hirtum (OH), and O. majorana (OM) were collected from a greenhouse located in the high altitude Sabana de Bogotá (Savanna of Bogotá) and O. vulgare L. ssp. hirtum (OG) produced and ground in Greece. Oregano essential oils (OEO) from these plants were obtained by steam distillation and analyzed by gas chromatography coupled to a mass spectrometer. Six treatments were evaluated: 200 mg/kg of OEO from OH, OL, and OM, 50 mg/kg of OEO from OG, 500 mg/kg of chlortetracycline, and without additives. Broiler chicks were maintained at 2,600 m above sea level, placed in brooder cages under a completely randomized design. Template DNA was isolated from duodenal, jejunal, ileal, and cecal contents in each group and bacterial 16S rDNA patterns were analyzed by denaturing gradient gel electrophoresis. Dendrograms of denaturing gradient gel electrophoresis band patterns revealed 2 main clusters, OEO-treated chicks and nontreated control chicks, in each intestinal segment. Band patterns from different gut compartments revealed major bacterial population shifts in the foregut (duodenum, jejunum, and ileum) compared with the hindgut (cecum and colon) at all ages evaluated (P < 0.05). The OEO groups showed less shift (62.7% similarity coefficient) between these 2 compartments versus the control groups (53.7% similarity coefficient). A reduction of 59% in mortality from ascites was seen in additive-supplemented groups compared with the control group. This study represents the first work to evaluate the effects of the 3 main chemotypes of Origanum genus in broilers.

Study of Stress Induced Failure of the Blood-gas Barrier and the Epithelial-epithelial Cells Connections of the Lung of the Domestic Fowl, Gallus gallus Variant Domesticus after Vascular Perfusion

Complete blood-gas barrier breaks (BGBBs) and epithelial-epithelial cells connections breaks (E-ECCBs) were enumerated in the lungs of free range chickens, Gallus gallus variant domesticus after vascular perfusion at different pressures. The E-ECCBs surpassed the BGBBs by a factor of ~2. This showed that the former parts of the gas exchange tissue were structurally weaker or more vulnerable to failure than the latter. The differences in the numbers of BGBBs and E-ECCBs in the different regions of the lung supplied with blood by the 4 main branches of the pulmonary artery (PA) corresponded with the diameters of the blood vessels, the angles at which they bifurcated from the PA, and the positions along the PA where they branched off. Most of the BGBBs and the E-ECCBs occurred in the regions supplied by the accessory- and the caudomedial branches: the former is the narrowest branch and the first blood vessel to separate from the PA while the latter is the most direct extension of the PA and is the widest. The E-ECCBs appeared to separate and fail from tensing of the blood capillary walls, as the perfusion- and intramural pressures increased. Compared to the mammalian lungs on which data are available, i.e., those of the rabbit, the dog, and the horse, the blood-gas barrier of the lung of free range chickens appears to be substantially stronger for its thinness.

Effects of N,N-dimethylglycine sodium salt on apparent digestibility, vitamin E absorption, and serum proteins in broiler chickens fed a high- or low-fat diet

The objective of this study was to assess the effect of supplementation with sodium salt of N,N-dimethylglycine (DMG-Na) on apparent digestibility (AD) in broiler chickens fed low- and high-fat diets. Twenty-eight 1-d-old broiler chickens were fed one of the dietary treatments: a low-fat diet (LF) or a high-fat diet (HF) supplemented with or without 1,000 mg/kg of DMG-Na. Body weight and feed consumption were recorded at 14 and 35 d of age. Average daily growth, daily feed intake, and feed conversion ratio were calculated. The AD of DM, organic matter (OM), CP, total fat (TF), and α-tocopheryl-acetate were assessed by 2 digestibility trials (at 18-21 and 32-35 d, respectively). Serum protein and plasma α-tocopherol concentrations were assessed at 35 d of age. Final BW, feed intake, carcass, breast, and spleen weight were higher in groups fed LF than HF diets (P = 0.048, P = 0.002, P = 0.039, P < 0.001, P = 0.007, respectively). Liver weight was increased in DMG-Na-unsupplemented groups (P = 0.011) for both fat levels. During the first digestibility trial (18-21 d), the AD of DM (P = 0.023), OM (P = 0.033), CP (P = 0.030), and α-tocopheryl-acetate (P = 0.036) was higher in the DMG-Na-supplemented group than control. Digestibility of total fat was increased by DMG-Na supplementation in the LF groups (P = 0.038). A trend for improvement of digestibility was observed during the second digestibility trial (32-35 d) for DM (P = 0.089), OM (P = 0.051), and CP (P = 0.063) in DMG-Na groups. Total serum proteins (and relative fractions) were positively influenced by DMG-Na supplementation both in LF and HF diets (P = 0.029). Plasma α-tocopherol concentration was higher in groups fed LF than HF diets (P < 0.001).

Sodium hydrosulfide prevents hypoxia-induced pulmonary arterial hypertension in broilers

1. The aim of the study was to determine if H(2)S is involved in the development of hypoxia-induced pulmonary hypertension in broilers, a condition frequently observed in a variety of cardiac and pulmonary diseases. 2. Two-week-old broilers were reared under normoxic conditions or exposed to normobaric hypoxia (6 h/day) with tissue levels of H(2)S adjusted by administering sodium hydrosulfide (NaHS, 10 µmol/kg body weight/day). Mean pulmonary arterial pressure, right ventricular mass, plasma and tissue H(2)S levels, the expression of cystathionine-β-synthase (CSE) and vascular remodeling were determined at 35 d of age. 3. Exposure to hypoxia-induced pulmonary arterial hypertension was characterized by elevated pulmonary pressure, right ventricular hypertrophy and vascular remodeling. This was accompanied by decreased expression of CSE and decreased concentrations of plasma and tissue H(2)S. 4. Hypoxia-induced pulmonary hypertension was significantly reduced by administration of NaHS but this protective effect was largely abolished by D, L-propargylglycerine, an inhibitor of CSE. 5. The results indicate that H(2)S is involved in the development of hypoxia-induced pulmonary hypertension. Supplementing NaHS or H(2)S could be a strategy for reducing hypoxia-induced hypertension in broilers.

Broiler ascites syndrome: collateral damage from efficient feed to meat conversion

Chickens have been raised as food for human consumption for over 4000 years. Over this time they have been continuously selected for specific desirable characteristics by active selection of parents to produce birds which fit perceived needs. Despite this long history of selective breeding and improvements in rearing techniques, the efficiency with which broiler meat is produced has shown a remarkable leap in recent decades. Persistent selection for rapid growth, high feed utilisation efficiency and large cut yield has resulted in modern meat-type poultry lines with superior genetic potential with regard to productivity. However, mortality and the incidence of metabolic diseases has increased in parallel with growth rate. One such disease is broiler ascites syndrome, which has been shown to be closely associated with the fast growth and high meat yield resulting from intense selection and with modern rearing techniques. The review is focused on the historical background, pathogenesis, epidemiology and prevention of broiler ascites syndrome in modern broiler production.

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.

Structural failures of the blood-gas barrier and the epithelial-epithelial cell connections in the different vascular regions of the lung of the domestic fowl, Gallus gallus variant domesticus, at rest and during exercise

Structural failure of blood–gas barrier (BGB) and epithelial–epithelial cell connections (EECCs) in different vascular regions of the exchange tissue of the lung was studied in rested and exercised chickens. The number of red blood cells (nRBCs) was counted and protein concentration (PC) measured after lavaging the respiratory system, and blood was sampled to determine the blood lactate levels (BLLs). The numbers of complete BGB breaks (nBGBBs) and those of the EECCs (nEECCBs) were counted in the different vascular territories of the lung. The nRBCs and the PCs increased with increasing exercise intensities but the rate of increase decreased at higher workloads. From rest to the fastest experimental treadmill speed of 2.95 m.sec⁻¹, BLLs increased 4-fold. In all cases, the nEECCBs exceeded those of the BGB, showing that structurally the BGB is relatively weaker than the EECC. The increase in the number of breaks with increasing exercise can be attributed to increase in the pulmonary capillary blood pressure (PCBP) from faster heart rates and higher cardiac outputs, while the leveling out of the measurements made at higher workloads may have arisen from hemodynamic changes that initially ensued from exudation of blood plasma and then flow of blood into the air capillaries on failure of the BGB. The relative differences in the nBGBBs and the nEECCBs in the different vascular regions of the lung were ascribed to diameters of the branches and their points of origin and angles of bifurcation from the pulmonary artery. Presence of RBCs in the air capillaries of the lungs of rested chickens showed that failure of the BGB commonly occurs even in healthy and unstressed birds. Rapid repair and/or defense responses, which were observed, may explain how birds cope with mechanical injuries of the BGB.

Changes of hepatic biochemical parameters and proteomics in broilers with cold-induced ascites

Ascites syndrome is still a problem for chicken industry in various parts of the world. Despite the intensive investigations of this syndrome for many years, its pathogenesis remains unclear. The objective of this study was to analyze the difference in hepatic proteomics between ascites and healthy broilers by two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS). Changes of biochemical parameters of liver and blood were also determined. The results indicated that red blood cell counts (RBC), hematocrit (HCT) and haemoglobin (HGB) of ascites broilers were significantly greater than healthy broilers. Hepatic malondialdehyde (MDA) level of ascites broilers was significantly increased, and the activity of total superoxide dismutase (T-SOD) was significantly decreased. Hepatic lactic acid (LD) level of ascitic broilers were significantly lower than healthy ones. Serum glucose and cholesterol level of ascites broilers were significantly increased, and serum globulin level was significantly decreased in ascites broilers. There was no significant difference in triglyceride (TG) and blood urea nitrogen (BUN) level. The activity of liver hexokinase (HK) and succinodehydrogenase (SDH) in ascites broilers was significantly decreased, and there was no significant difference in the activity of liver pyruvate kinase (PK) and Na+-K+-ATPase. The hepatic proteomics analysis showed that 18 proteins expression difference were identified between ascites and healthy broilers. These proteins were mainly involved in: 1) cytoskeleton; 2) glucose, lipids and amino acid metabolism; 3) cell secretion; 4) cell apoptosis; 5) signal transduction; 6) immune and inflammatory response; and 7) cellular redox homeostasis. Mitochondrial isoform phosphoenolpyruvate carboxykinase (M-PEPCK) mainly participates in gluconeogenesis of chicken liver. In conclusion, liver oxidative damage was significantly aggravated, but antioxidant capacity was decreased in cold-induced ascites broilers. Serum glucose level was significantly increased, with liver M-PEPCK expression higher in ascites broilers, which implied that some potential regulatory reagents may reduce ascites susceptibility and mortality under cold temperature by increasing liver gluconeogenesis level.

Calcium antagonists, diltiazem and nifedipine, protect broilers against low temperature-induced pulmonary hypertension and pulmonary vascular remodeling

This study was designed to determine whether calcium antagonists, diltiazem and nifedipine, can depress low temperature-induced pulmonary hypertension (PH) in broilers (also known as ascites) and to characterize their efficacy on hemodynamics and pulmonary artery function. Chicks were randomly allocated into six experimental groups and orally administered with vehicle, 5.0 mg/kg body weight (BW)/12 h nifedipine or 15.0 mg/kg BW/12 h diltiazem from 16 to 43 days of age under low temperature. The mean pulmonary arterial pressure (mPAP), the ascites heart index (AHI), the erythrocyte packed cell volume (PCV) and the relative percentage of medial pulmonary artery thickness were examined on days 29, 36 and 43. The data showed that administration of diltiazem protected broilers from low temperature-induced pulmonary hypertension and vascular remodeling. Although nifedipine prevented mPAP from increasing during the early stage, it did not suppress the development of PH during the late stage and did not keep heart rate (HR), PCV, AHI and the thickness of pulmonary small artery smooth muscle layer at the normal levels. Taken together, our results showed that diltiazem can effectively prevent low temperature-induced pulmonary hypertension in broilers with fewer side-effects and may be a potential compound for the prevention of this disease in poultry industry.

Recent advances into understanding some aspects of the structure and function of mammalian and avian lungs

Recent findings are reported about certain aspects of the structure and function of the mammalian and avian lungs that include (a) the architecture of the air capillaries (ACs) and the blood capillaries (BCs); (b) the pulmonary blood capillary circulatory dynamics; (c) the adaptive molecular, cellular, biochemical, compositional, and developmental characteristics of the surfactant system; (d) the mechanisms of the translocation of fine and ultrafine particles across the airway epithelial barrier; and (e) the particle-cell interactions in the pulmonary airways. In the lung of the Muscovy duck Cairina moschata, at least, the ACs are rotund structures that are interconnected by narrow cylindrical sections, while the BCs comprise segments that are almost as long as they are wide. In contrast to the mammalian pulmonary BCs, which are highly compliant, those of birds practically behave like rigid tubes. Diving pressure has been a very powerful directional selection force that has influenced phenotypic changes in surfactant composition and function in lungs of marine mammals. After nanosized particulates are deposited on the respiratory tract of healthy human subjects, some reach organs such as the brain with potentially serious health implications. Finally, in the mammalian lung, dendritic cells of the pulmonary airways are powerful agents in engulfing deposited particles, and in birds, macrophages and erythrocytes are ardent phagocytizing cellular agents. The morphology of the lung that allows it to perform different functions-including gas exchange, ventilation of the lung by being compliant, defense, and secretion of important pharmacological factors-is reflected in its "compromise design."

Phenotypic plasticity and genetic adaptation to high-altitude hypoxia in vertebrates

High-altitude environments provide ideal testing grounds for investigations of mechanism and process in physiological adaptation. In vertebrates, much of our understanding of the acclimatization response to high-altitude hypoxia derives from studies of animal species that are native to lowland environments. Such studies can indicate whether phenotypic plasticity will generally facilitate or impede adaptation to high altitude. Here, we review general mechanisms of physiological acclimatization and genetic adaptation to high-altitude hypoxia in birds and mammals. We evaluate whether the acclimatization response to environmental hypoxia can be regarded generally as a mechanism of adaptive phenotypic plasticity, or whether it might sometimes represent a misdirected response that acts as a hindrance to genetic adaptation. In cases in which the acclimatization response to hypoxia is maladaptive, selection will favor an attenuation of the induced phenotypic change. This can result in a form of cryptic adaptive evolution in which phenotypic similarity between high- and low-altitude populations is attributable to directional selection on genetically based trait variation that offsets environmentally induced changes. The blunted erythropoietic and pulmonary vasoconstriction responses to hypoxia in Tibetan humans and numerous high-altitude birds and mammals provide possible examples of this phenomenon. When lowland animals colonize high-altitude environments, adaptive phenotypic plasticity can mitigate the costs of selection, thereby enhancing prospects for population establishment and persistence. By contrast, maladaptive plasticity has the opposite effect. Thus, insights into the acclimatization response of lowland animals to high-altitude hypoxia can provide a basis for predicting how altitudinal range limits might shift in response to climate change.

Molecular evolution of cytochrome C oxidase underlies high-altitude adaptation in the bar-headed goose

Bar-headed geese (Anser indicus) fly at up to 9,000 m elevation during their migration over the Himalayas, sustaining high metabolic rates in the severe hypoxia at these altitudes. We investigated the evolution of cardiac energy metabolism and O(2) transport in this species to better understand the molecular and physiological mechanisms of high-altitude adaptation. Compared with low-altitude geese (pink-footed geese and barnacle geese), bar-headed geese had larger lungs and higher capillary densities in the left ventricle of the heart, both of which should improve O(2) diffusion during hypoxia. Although myoglobin abundance and the activities of many metabolic enzymes (carnitine palmitoyltransferase, citrate synthase, 3-hydroxyacyl-coA dehydrogenase, lactate dehydrogenase, and pyruvate kinase) showed only minor variation between species, bar-headed geese had a striking alteration in the kinetics of cytochrome c oxidase (COX), the heteromeric enzyme that catalyzes O(2) reduction in oxidative phosphorylation. This was reflected by a lower maximum catalytic activity and a higher affinity for reduced cytochrome c. There were small differences between species in messenger RNA and protein expression of COX subunits 3 and 4, but these were inconsistent with the divergence in enzyme kinetics. However, the COX3 gene of bar-headed geese contained a nonsynonymous substitution at a site that is otherwise conserved across vertebrates and resulted in a major functional change of amino acid class (Trp-116 → Arg). This mutation was predicted by structural modeling to alter the interaction between COX3 and COX1. Adaptations in mitochondrial enzyme kinetics and O(2) transport capacity may therefore contribute to the exceptional ability of bar-headed geese to fly high.

Congestive Heart Failure in 6 African Grey Parrots (Psittacus e erithacus)

Six African grey parrots ( Psittacus e erithacus) were diagnosed with cardiomyopathy and congestive heart failure based on gross and microscopic findings. Ages ranged from 15 days to 8 years, and 5 of 6 parrots were either neonates or juveniles at the time of diagnosis. Two neonates and 2 juveniles came from the same breeding aviary; the 2 juveniles were born to the same breeding pair. The 2 other parrots were kept as pets. Clinical signs included distention of the coelomic cavity (4 of 6), rales (3 of 6), weakness (4 of 6), bradyarrhythmia (1 of 6), growth retardation (1 of 6), crop stasis (1 of 6), and regurgitation (1 of 6). Three parrots were euthanized and 3 died. Gross findings included cardiomegaly due to biventricular, right-, or left-sided cardiomyopathy (6 of 6); coelomic effusion (6 of 6); whitish or yellow foci in the liver (6 of 6); atrophy of the liver (particularly, the left lobe; 5 of 6); reddened or grey lungs (5 of 6); subcutaneous edema (2 of 6); hydropericardium (1 of 6); and bilateral thyroid gland enlargement (1 of 6). Relevant microscopic findings included passive hepatic congestion (6 of 6) and pulmonary congestion (2 of 6), lymphocytic thyroiditis (2 of 6), and diffuse thyroid follicular hyperplasia (2 of 6). Microscopically, the heart was unremarkable (2 of 6) or had mild lymphocytic myocarditis (2 of 6), mild multifocal cytoplasmic vacuolation of cardiomyocytes (2 of 6), mild lymphocytic myocardial (Purkinje cell) ganglioneuritis (1 of 6), and mild multifocal interstitial fibrosis and nuclear hypertrophy of cardiomyocytes (1 of 6). One parrot had concurrent proventricular dilatation disease (systemic ganglioneuritis). The cause of cardiomyopathy in these parrots was not determined.

Physiological parameters in broiler lines divergently selected for the incidence of ascites

Ascites syndrome (AS) is manifested in flocks of contemporary broilers that are allowed to fully manifest their genetic potential for rapid growth. After successful selection, a pair of divergent lines was established, AS-susceptible (AS-S) and AS-resistant (AS-R). These lines facilitate comparisons between genetically resistant and susceptible healthy young broilers when reared under standard brooding conditions (SBC). The aim of the present study was to look for predictive indicators for AS susceptibility by comparing relevant physiological parameters in the AS-S and AS-R lines under SBC and after exposure to extreme ascites-inducing conditions (AIC). In this design, a trait differing significantly between the 2 lines under SBC is expected to be a reliable indicator for selection against AS susceptibility in breeding stocks when reared under noninducing conditions. Males from the AS-S and AS-R lines were reared together under SBC to 19 d of age, then under the AIC protocol. Cumulative incidence of AS mortality was 93.2% in the AS-S line and only 9% in the AS-R line, confirming the genetic divergence between the lines. Exposure to AIC enhanced the imbalance between oxygen demands and supply in the AS-S birds and induced differences in blood parameter level between the 2 lines. The AS-S birds exhibited elevated hematocrit and red blood cell counts and a decline in oxygen saturation in the arterial blood. No difference in hemoglobin concentration was found, but calculation of hemoglobin content per 1,000 red blood cells revealed a significant reduction in hemoglobin content in the AS-S birds. Under SBC, there were no significant differences between the lines for hematocrit, red blood cell count, hemoglobin concentration, hemoglobin count per 1,000 red cells, and blood oxygen saturation. However, heart rate during the first week of life was significantly higher in the AS-S birds than in the AS-R birds on d 1 and 7, suggesting that high heart rate may potentially serve as an early criterion for selection against AS susceptibility.

Comparative in vitro study of interactions between particles and respiratory surface macrophages, erythrocytes, and epithelial cells of the chicken and the rat

In mammals, surface macrophages (SMs) play a foremost role in protecting the respiratory system by engulfing and destroying inhaled pathogens and harmful particulates. However, in birds, the direct defense role(s) that SMs perform remains ambiguous. Paucity and even lack of SMs have been reported in the avian respiratory system. It has been speculated that the pulmonary defenses in birds are inadequate and that birds are exceptionally susceptible to pulmonary diseases. In an endeavour to resolve the existing controversy, the phagocytic capacities of the respiratory SMs of the domestic fowl and the rat were compared under similar experimental conditions by exposure to polystyrene particles. In cells of equivalent diameters (8.5 microm in the chicken and 9.0 microm in the rat) and hence volumes, with the volume density of the engulfed polystyrene particles, i.e. the volume of the particles per unit volume of the cell (SM) of 23% in the chicken and 5% in the rat cells, the avian cells engulfed substantially more particles. Furthermore, the avian SMs phagocytized the particles more efficiently, i.e. at a faster rate. The chicken erythrocytes and the epithelial cells of the airways showed noteworthy phagocytic activity. In contrast to the rat cells that did not, 22% of the chicken erythrocytes phagocytized one to six particles. In birds, the phagocytic efficiencies of the SMs, erythrocytes, and epithelial cells may consolidate pulmonary defense. The assorted cellular defenses may explain how and why scarcity of SMs may not directly lead to a weak pulmonary defense. The perceived susceptibility of birds to respiratory diseases may stem from the human interventions that have included extreme genetic manipulation and intensive management for maximum productivity. The stress involved and the structural-functional disequilibria that have occurred from a 'directed evolutionary process', rather than weak immunological and cellular immunity, may explain the alleged vulnerability of the avian gas exchanger to diseases.

Minimal distensibility of pulmonary capillaries in avian lungs compared with mammalian lungs

Previous physiological studies suggest that avian pulmonary capillaries behave like almost rigid tubes. We made morphometric measurements to determine the diameter of the capillaries in chicken lungs when the transmural pressure was altered over a wide range. The diameter of avian pulmonary capillaries increased by only 13% when the pressure inside them was raised from 0 to 25 cmH(2)O. In contrast, other studies have shown that the mean width of the pulmonary capillaries in dogs increased by about 125% and in cats by 128% for the same pressure change. Furthermore, raising the pressure 35 cmH(2)O outside the capillaries compared to the pressure inside the capillaries in chicken lungs caused little change in diameter whereas under the same conditions in mammal lungs the capillaries are completely collapsed. We conclude that the epithelial bridges between the blood capillaries in the bird lung provide strong support to the capillaries both in expansion and compression.

Comparative study of myocardial high energy phosphate substrate content in slow and fast growing chicken and in chickens with heart failure and ascites

In order to explain the biochemical mechanisms associated with deteriorating heart function in broiler chickens, this study compared myocardial high energy phosphate substrates in leghorns, feed restricted (Broilers-Res) broilers, ad libitum fed broilers (Broilers-AL), and in broilers that developed heart failure and ascites. The profile of adenine nucleotide content in the heart tissue did not differ between leghorns and Broilers-Res, but there were significant differences among Broilers-Res, Broilers-AL, and broilers with ascites. During intensive growth periods, leghorns and Broilers-Res showed increasing trends in heart ATP levels, whereas in fast growing broilers the heart ATP declined (p<0.021). ATP:ADP and ATP:CrP ratios increased with age in both leghorn and Broilers-Res, declined in fast growing broilers, and were the lowest in broilers that developed heart failure. The changes in heart high energy phosphate profile in broilers suggest that the energy demand of the heart during a rapid growth phase may exceed the bird's metabolic capacity to supply adequate levels of high energy phosphate substrate. The insufficiency of energy substrate likely contributes to the declining heart rate. In some individuals this may lead to impaired heart pump function, and in more severe cases may progress to heart pump failure.

Avian proteomics: advances, challenges and new technologies

Proteomics is defined as an analysis of the full complement of proteins of a cell or tissue under given conditions. Avian proteomics, or more specifically chicken proteomics, has focussed on the study of individual tissues and organs of interest to specific researchers. Researchers have looked at skeletal muscle and growth, and embryonic development and have performed initial studies in avian disease. Traditional proteomics involves identifying and cataloguing proteins in a cell and identifying relative changes in populations between two or more states, be that physiological or disease-induced states. Recent advances in proteomic technologies have included absolute quantification, proteome simplification and the ability to determine the turnover of individual proteins in a global context. This review discusses the current developments in this relatively new field, new technologies and how they may be applied to biological questions, and the challenges faced by researchers in this ever-expanding and exciting field.

Endothelin 1, its Endothelin Type A Receptor, Connective Tissue Growth Factor, Platelet-Derived Growth Factor, and Adrenomedullin Expression in Lungs of Pulmonary Hypertensive and Nonhypertensive Chickens

Twenty-four 1-d-old broilers were distributed in 2 groups, pulmonary hypertensive broilers (PHB) and pulmonary nonhypertensive broilers (NPHB), to estimate possible differences between them in the expression of endothelin 1 (ET-1) and its type A receptor, connective tissue growth factor, platelet-derived growth factor, and adrenomedullin expression in the lungs. For this purpose, total RNA extraction and real-time PCR analysis were used. Endothelin 1 mRNA levels in the lungs of PHB were significantly higher than the corresponding level in NPHB (P < 0.001). In contrast, the opposite was true for ET-1 type A receptor mRNA levels (P < 0.001). Connective tissue growth factor mRNA levels in the lungs of PHB were significantly higher than in the lungs of NPHB (P < 0.01). However, no differences were encountered between the 2 groups of broilers in platelet-derived growth factor mRNA expression (P > 0.05). Adrenomedullin mRNA levels in the lungs of PHB were significantly higher than in NPHB (P < 0.01). It has been demonstrated for the first time that ET-1, connective tissue growth factor, and adrenomedullin are upregulated in the lungs of PHB. Furthermore, it is suggested that these peptides may play a major role in pulmonary hypertension pathophysiology. Present data might provide clues for future research directions such as genetic selection and therapeutic intervention to revert the process of pulmonary vasoconstriction and vascular remodeling. Major research goals could be to find endothelium-derived factors that probably trigger endothelial dysfunction, as well as possible interactions with already identified molecules which also intervene in the pulmonary response to hypoxia.

Evaluation of Growth Rate, Body Weight, Heart Rate, and Blood Parameters as Potential Indicators for Selection Against Susceptibility to the Ascites Syndrome in Young Broilers

The continuous selection for rapid growth has been accompanied by an increasing occurrence of ascites syndrome (AS), which develops in broilers failing to supply the increasing demand for O(2) in their bodies. Moderate heritability has been reported for AS in broiler populations, suggesting that selection against AS is feasible. However, direct selection based on AS mortality requires exposure of candidate birds to AS-inducing conditions (AIC), which hinder selection for performance traits. Noninvasive indicators of AS, expressed under standard husbandry, may facilitate the integration of selection against AS into breeding programs. This study was designed to look for differences in heart rate, hematocrit, O(2) saturation of hemoglobin in arterial blood (SaO(2)), BW, and weight gain, all measured at early ages under standard brooding conditions, between birds that later developed AS and those that remained healthy under AIC, and to estimate the heritability of these AS-related parameters and their genetic correlation with the tendency of broilers to develop AS. The experimental population was derived from a broiler dam line. Male progeny of 34 half-sib sire families were reared under standard brooding conditions to 19 d of age, then under an AIC protocol consisting of housing in individual cages, cool air high-speed ventilation, and growth enhancement using high-energy pelleted feed and 23 h/d of light. Birds were necropsied upon mortality or at the end of the trials and were recorded as being susceptible, with manifestations of AS (SUS), or resistant and healthy (RES). About 44% developed AS, confirming the efficacy of the novel AIC protocol. The SUS and RES chicks did not differ in BW and weight gain up to 19 d of age, suggesting that there was no association between AS susceptibility and rapid early growth. The SUS chicks exhibited lower SaO(2) and heart rate than the RES chicks. Moderate heritability was estimated for all traits, but only SaO(2) exhibited consistently significant genetic correlation (-0.5) with AS, suggesting that it may serve as an early indicator for selection against AS, albeit with a limited efficacy.

Calcium antagonist verapamil prevented pulmonary arterial hypertension in broilers with ascites by arresting pulmonary vascular remodeling

Calcium signaling has been reported to be involved in the pathogenesis of hypertension. Verapamil, one of the calcium antagonists, is used to characterize the role of calcium signaling in the development of pulmonary arterial hypertension syndrome in broilers. The suppression effect of verapamil on pulmonary arterial hypertension and pulmonary vascular remodeling was examined in broilers, from the age of 16 days to 43 days. Our results showed that oral administration of lower dose of verapamil (5 mg/kg body weight every 12 h) prevented the mean pulmonary arterial pressure, the ascites heart index and the erythrocyte packed cell volume of birds at low temperature from increasing, the heart rate from decreasing, and pulmonary arteriole median from thickening, and no pulmonary arteriole remodeling in broilers treated with the two doses of verapamil at low temperature was observed. Our results indicated that calcium signaling was involved in the development of broilers' pulmonary arterial hypertension, which leads to the development of ascites, and we suggest that verapamil may be used as a preventive agent to reduce the occurrence and development of pulmonary arterial hypertension in broilers.

Major differences in the pulmonary circulation between birds and mammals

The lungs of domestic chickens were perfused with blood or dextran/saline and the pulmonary artery pressure (P(a)) and venous pressure (P(v)) were varied in relation to air capillary pressure (P(A)). In Zone 3 conditions, pulmonary vascular resistance (PVR) was virtually unchanged with increases in either P(a) or P(v). This is very different behavior from mammals where the same interventions greatly reduce PVR. In Zone 2 conditions blood flow was essentially independent of P(v) as in mammalian lungs but all the capillaries appeared to be open, apparently incompatible with a Starling resistor mechanism. In Zone 1 the capillaries were open even when P(A) exceeded P(a) by over 30 cm H(2)O which is very different behavior from that of the mammalian lung. We conclude that the air capillaries that surround the blood capillaries provide rigid support in both compression and expansion of the vessels. The work suggests a pathogenesis for pulmonary hypertension syndrome in chickens which costs the broiler industry $1 billion per year.

Genetic mapping of quantitative trait loci affecting susceptibility in chicken to develop pulmonary hypertension syndrome

Pulmonary hypertension syndrome (PHS), also referred to as ascites syndrome, is a growth-related disorder of chickens frequently observed in fast-growing broilers with insufficient pulmonary vascular capacity at low temperature and/or at high altitude. A cross between two genetically different broiler dam lines that originated from the White Plymouth Rock breed was used to produce a three-generation population. This population was used for the detection and localization of quantitative trait loci (QTL) affecting PHS-related traits. Ten full-sib families consisting of 456 G2 birds were typed with 420 microsatellite markers covering 24 autosomal chromosomes. Phenotypic observations were collected on 4202 G3 birds and a full-sib across family regression interval mapping approach was used to identify QTL. There was statistical evidence for QTL on chicken chromosome 2 (GGA2), GGA4 and GGA6. Suggestive QTL were found on chromosomes 5, 8, 10, 27 and 28. The most significant QTL were located on GGA2 for right and total ventricular weight as percentage of body weight (%RV and %TV respectively). A related trait, the ratio of right ventricular weight as percentage to total ventricular weight (RATIO), reached the suggestive threshold on this chromosome. All three QTL effects identified on GGA2 had their maximum test statistic in the region flanked by markers MCW0185 and MCW0245 (335-421 cM).

Comparison of three lines of broilers differing in ascites susceptibility or growth rate. 2. Egg weight loss, gas pressures, embryonic heat production, and physiological hormone levels

Ascites is a metabolic disorder that accounts for over 25% of overall mortality in the broiler industry. This disorder is manifested between wk 5 and 6 posthatch, but there are previous indications that predisposition may be identified during embryonic development. In this current study, we determined embryonic physiological and metabolic parameters that may be associated with ascites predisposition. For this purpose, we used broiler eggs from 3 lines that differed in ascites sensitivity. These included an ascites-sensitive dam line (DAS), an ascites-resistant dam line (DAR), and an ascites-sensitive sire line (SASL). Eggs were incubated for 21 d under standard conditions. The following parameters were measured during incubation: egg weights at setting, egg weight losses at 18 d, embryo body weights and embryo heart weights throughout development, air cell partial gas pressures (pCO2 and pO2) levels at d 18 and at internal pipping (IP); plasma triiodothyronine, thyroxine, and corticosterone levels at d 18, IP, and hatch; heat production from d 17 until hatch, hematocrit values at hatch, and posthatch growth rate to 7 d along with hematocrit values. The data obtained revealed that selection for ascites sensitivity or rapid growth rate had no consistent influence on some of these parameters such that they could be wholly associated with ascites sensitivity for predictive purposes. Whereas differences in embryonic developmental patterns were apparent throughout embryonic development, these differences in physiological and metabolic parameters may be due partly to genetic differences unrelated to ascites sensitivity.