Further evidence for the involvement of cardiac beta-adrenergic receptors in right ventricle hypertrophy and ascites in broiler chickens

Chicken Incubation Conditions: Role in Embryo Development, Physiology and Adaptation to the Post-Hatch Environment

The chicken hatching egg is a self-contained life-supporting system for the developing embryo. However, the post-hatch performance of birds depends on several factors, including the breeder management and age, egg storage conditions and duration before incubation, and the incubation conditions. Studies have determined the effect of incubation factors on chick post-hatch growth potential. Therefore, chick physical quality at hatch is receiving increasing attention. Indeed, although incubation temperature, humidity, turning and ventilation are widely investigated, the effects of several variables such as exposure of the embryo to high or low levels, time of exposure, the amplitude of variations and stage exposures on embryo development and post-hatch performance remain poorly understood. This review paper focuses on chick quality and post-hatch performance as affected by incubation conditions. Also, chick physical quality parameters are discussed in the context of the parameters for determining chick quality and the factors that may affect it. These include incubation factors such as relative humidity, temperature, turning requirements, ventilation, in ovo feeding and delay in feed access. All these factors affect chick embryo physiology and development trajectory and consequently the quality of the hatched chicks and post-hatch performance. The potential application of adapted incubation conditions for improvement of post-hatch performance up to slaughter age is also discussed. It is concluded that incubation conditions affect embryo parameters and consequently post-hatch growth differentially according to exposure time and stage of exposure. Therefore, classical physical conditions are required to improve hatchability, chick quality and post-hatch growth.

Genome-Wide Assessment of DNA Methylation in Chicken Cardiac Tissue Exposed to Different Incubation Temperatures and CO2 Levels

Temperature and CO₂ concentration during incubation have profound effects on broiler chick development, and numerous studies have identified significant effects on hatch heart weight (HW) as a result of differences in these parameters. Early life environment has also been shown to affect broiler performance later in life; it has thus been suggested that epigenetic mechanisms may mediate long-term physiological changes induced by environmental stimuli. DNA methylation is an epigenetic modification that can confer heritable changes in gene expression. Using reduced-representation bisulfite sequencing (RRBS), we assessed DNA methylation patterns in cardiac tissue of 84 broiler hatchlings incubated at two egg shell temperatures (EST; 37.8°C and 38.9°C) and three CO₂ concentrations (0.1%, 0.4%, and 0.8%) from day 8 of incubation onward. We assessed differential methylation between EST treatments and identified 2,175 differentially methylated (DM) CpGs (1,121 hypermethylated, 1,054 hypomethylated at 38.9° vs. 37.8°) in 269 gene promoters and 949 intragenic regions. DM genes (DMGs) were associated with heart developmental processes, including cardiomyocyte proliferation and differentiation. We identified enriched binding motifs among DM loci, including those for transcription factors associated with cell proliferation and heart development among hypomethylated CpGs that suggest increased binding ability at higher EST. We identified 9,823 DM CpGs between at least two CO₂ treatments, with the greatest difference observed between 0.8 and 0.1% CO₂ that disproportionately impacted genes involved in cardiac muscle development and response to low oxygen levels. Using HW measurements from the same chicks, we performed an epigenome-wide association study (EWAS) for HW, and identified 23 significantly associated CpGs, nine of which were also DM between ESTs. We found corresponding differences in transcript abundance between ESTs in three DMGs (ABLIM2, PITX2, and THRSP). Hypomethylation of an exonic CpG in PITX2 at 38.9°C was associated with increased expression, and suggests increased cell proliferation in broiler hatchlings incubated at higher temperatures. Overall, these results identified numerous epigenetic associations between chick incubation factors and heart development that may manifest in long-term differences in animal performance.

Effect of carbon dioxide during the early stage of duck egg incubation on hatching characteristics and duckling performance

Gaseous exchange is very important for embryonic development during the incubation of bird eggs. The present study was carried out to investigate the effect of carbon dioxide (CO₂) pumping during the first 10 days of Pekin duck egg incubation on hatching characteristics, embryonic growth, hormonal concentrations and the post-hatch weight of the ducks. Two different ventilation conditions were used in this study. In one condition (V), the incubator was ventilated standard. In the other condition (NV), CO₂ was gradually pumped into a non-ventilated incubator to reach and maintain a 1% concentration through the first 10 days of incubation, after which the incubator was ventilated for the rest of the incubation period. The CO₂ percentage in the V incubator was constant at approximately 0.18%; by contrast, in the NV incubator, the concentration was increased gradually from 0.17% to 1%, where it was maintained through the 10th day of incubation. Throughout the incubation period, the egg weight loss and the embryonic mortality percentages were significantly lower in NV than in V. The hatchability of fertile eggs and the weights of ducklings at hatch were significantly higher in NV than in V. The embryonic T₃, T₄ and corticosterone levels in NV were significantly higher than those in V. Additionally, the haematological parameters (haemoglobin, packed cell volume and red blood cells) of the embryos were significantly higher in NV than in V. Furthermore, a total of 1198 ducklings for the V and NV conditions, all one day old, were individually weighed and then transferred into randomly assigned floor pens with 3 replicates for each ventilation condition. The feed conversion ratio of the ducks was significantly lower in NV than in V, while the reverse was true of body weight at different ages. Therefore, we can conclude that the NV condition with circulation of CO₂ for the first 10 days of incubation is preferable to the V condition.

Temperature and CO2 during the hatching phase. I. Effects on chick quality and organ development

The objective of this study was to investigate the effect of eggshell temperature (EST) and carbon dioxide (CO2) concentration during only the hatching phase on embryonic development and chick quality. Three batches of eggs were incubated at an EST of 37.8°C until d of incubation (E) 19. From E19, embryos were incubated at low (36.7°C), normal (37.8°C), or high (38.9°C) EST and at low (0.2%) or high (1%) CO2 concentration. Organ growth and embryo and chick quality were measured at E19, internal pipping (IP), hatch, and 12 h after hatch. A few interactions between EST and CO2 were found at IP, hatch, and 12 h after hatch, but all of these interactions were temporary and in most cases weak. High EST resulted in a lower relative heart weight compared with low ( = 0.05) and normal EST ( = 0.06) at IP, compared with low ( = 0.11) and normal EST ( = 0.08) at hatch, and compared with low ( = 0.11) and normal EST ( = 0.08) at 12 h after hatch. At hatch, high EST resulted in a lower YFBM compared with low EST ( = 0.65). At 12 h after hatch, high EST resulted in a lower relative liver weight compared with low EST ( = 0.12). At low EST, greater relative intestinal weight was found compared with normal ( = 0.41) and high EST ( = 0.37). The effect of CO2 solely was found at 12 h after hatch at which a higher relative heart weight ( = 0.05) and a higher relative lung weight ( = 0.0542) was found at high CO2 compared with low CO2. High EST during only the hatching phase negatively affected chick development, mainly expressed by the lower relative heart weight at IP, hatch, and 12 h after hatch and lower YFBM at hatch. The resolving effect of CO2 demonstrates that CO2 only seem to have a temporary effect during the hatching phase.

Effect of oxygen supplementation in the hatcher at high altitude on the incubation results of broiler eggs laid at low altitude

1. The object of this research was to investigate the effects of high altitude with supplementary oxygen during the last stage of incubation of broiler eggs laid at low altitude and incubated at low and high altitude. We analysed thyroid hormones and haematological variables. 2. The treatment groups were: low altitude (LA), high altitude with oxygen supplementation in the hatcher (HA-OX) and high altitude non-oxygen-supplemented (HA-NOX). 3. High altitude affected relative egg weight loss and early embryonic mortality. The hatchability of fertile eggs was lower at high than at low altitude. 4. Oxygen supplementation into the hatcher cabinet during the last stage of incubation decreased late embryonic mortality ratio (LEM(1)) and improved survival rates of embryos incubated at high altitude. 5. Eggs incubated at low altitude had a higher hatched chick weight and relative chick weight than those incubated at high altitude. Hatched chick weight and relative chick weight did not change with oxygen supplementation at high altitude. 6. High altitude caused an increase in plasma T(3) and T(4) concentrations as well as in the ratio of T(3):T(4) in embryos. High altitude newly hatched chicks showed a higher T(3):T(4) ratio than low altitude chicks; this ratio decreased with oxygen supplementation at high altitude. Altitude and oxygen supplementation did not affect the mean plasma T(4). 7. Newly-hatched chicks incubated at high altitude showed a higher plasma haematocrit (PCV) than the newly-hatched chicks from eggs incubated at low altitude. High altitude without supplementation increased haemoglobin (Hb), while oxygen supplementation returned the value to low altitude values.

Improvement of cold resistance and performance of broilers by acute cold exposure during late embryogenesis

The aim of this study was to fine-tune previous acute cold exposure treatments of broiler embryos during late embryogenesis to improve lifelong cold resistance and performance. Six hundred Cobb hatching eggs were incubated under standard conditions and then exposed to 3 treatments: control; cold treatment in which embryos were exposed to 15°C for 30 min on d 18 and 19 of incubation (30 × 2); and cold treatment similar to 30 × 2 but with 60-min exposures (60 × 2). Egg shell temperature (T(egg)) and heart rate (HR) were monitored pre- and posttreatment. Upon hatching, hatchability, body weight, and body temperature were recorded. From 14 to 35 d of age, three quarters of the chickens in each treatment were raised under ascites-inducing conditions (AIC) and the remaining birds were raised under standard brooding conditions (SBC). The T(egg) and HR decreased significantly in response to increased exposure time on d 18 of incubation. On d 19 of incubation, before the second cold exposure, the 30 × 2 group showed greater T(egg) and HR than the controls, and during the second exposure they maintained these parameters better than the 60 × 2 embryos. No treatment effect on hatchability was observed. At 35 d of age ascites incidence among 30 × 2 chickens under AIC was significantly less than that among the controls (P < 0.01), and body weight of these chickens under either SBC or AIC was significantly higher than that of the controls. Under SBC relative breast muscle weight was significantly higher in 60 × 2 chickens, whereas the relative heart weight was higher in both cold-treated groups than in the controls. It can be concluded that repeated short acute cold exposures during late embryogenesis significantly reduced ascites incidence and improved growth rate under either SBC or AIC. These results may be related to a prenatal epigenetic adaptation of the thermoregulatory and cardiovascular systems to low ambient temperature.

The effects of feed restriction and ambient temperature on growth and ascites mortality of broilers reared at high altitude

The development of ascites was investigated in broilers at low versus high altitudes, cold versus normal ambient temperatures (AT), and 3 feeding regimens. One-day-old chicks obtained at sea level were reared at high altitude (highA; 1,720 m; n = 576) with 2 AT treatments, low AT from 3 wk onward at highA (highA/cold) and normal AT from 3 wk onward at highA (highA/norm), or at sea level (normal AT from 3 wk onward at low altitude, lowA/norm; n = 540). Under highA/cold, AT ranged between 16 to 17 degrees C in the fourth week, 17 to 19 degrees C in the fifth week, and 19 to 21 degrees C thereafter. Under highA/norm and lowA/norm, AT was 24 degrees C in the fourth week and ranged between 22 to 24 degrees C thereafter. Broilers in each condition were divided into 3 groups: feed restriction (FR) from 7 to 14 d, FR from 7 to 21 d, and ad libitum (AL). Ascites mortality and related parameters were recorded. Low mortality (0.4%) occurred under lowA/norm conditions. Under highA/norm, mortality was lower in females (8.6%) than in males (13.8%) and was not affected by the feeding regimen. The highA/cold treatment resulted in higher mortality but only in males; it was 44.2% among highA/cold AL-fed males and only about 26% under the FR regimens, suggesting that FR helped some males to better acclimatize to the highA/cold environment and avoid ascites. However, mortality was only 13.3% in AL-fed males at highA/norm and FR did not further reduce the incidence of ascites under these conditions. Thus, avoiding low AT in the poultry house by slight heating was more effective than FR in reducing ascites mortality at highA. Compared with FR from 7 to 14 d, FR from 7 to 21 d did not further reduce mortality and reduced growth. At 47 d, the majority of surviving broilers at highA had high levels of hematocrit and right ventricle:total ventricle weight ratio (>0.29), but they were healthy and reached approximately the same BW as their counterparts at low altitude. This finding may suggest that in broilers reared at highA from day of hatch, the elevation in hematocrit and in right ventricle:total ventricle weight ratio happens gradually and therefore is not necessarily indicative of ascites development.

Partial pressure of carbon dioxide in the venous blood of young birds as a predictor of ascites susceptibility in broiler chickens

In order to investigate the relationship between carbon dioxide tensions in the venous blood of young chickens and ascites susceptibility, one hundred day-old chickens from two pure broiler breeder lines differing in susceptibility to ascites syndrome were obtained and reared at low environmental temperature. Weekly, blood samples were taken for the determination of blood gas parameters and plasma thyroid hormone levels. Dead birds were examined for lesions of ascites daily and all survived birds were autopsied at the end of the trials. In cold conditioning, the cumulative incidence of right ventricular hypertrophy (RVH) and ascites was 78% (39/50) in fast-growing (line A) and 50% (25/50) in slow-growing (line B) chickens, confirming that line A chickens had higher susceptibility to ascites than line B chickens. At 12 days of age, the mean pCO(2) tension was significantly (P < 0.01) higher in the venous blood of line A than line B chickens. During the experiment, the majority of line A and line B chickens showing RVH and ascites exhibited pCO(2) tensions equal to, or exceeding 50 mmHg at 12 days of age. Additionally, fast-growing chickens showed significantly lower plasma T3 and T4 concentrations than slow-growing chickens. In conclusion, our data indicate that carbon dioxide pressure in the venous blood of early postnatal broiler chickens could be used as a valuable predictor in the selection of birds susceptible to pulmonary hypertension and ascites. The function of thyroid hormones should also be taken into consideration in further selection procedures for meat-type chickens.

Further evidence for the involvement of anatomical parameters of the cardiopulmonary system in the development of ascites syndrome in broiler chickens

Eggs from a broiler line were incubated at two different altitudes and hatched. Relative heart and lung weights, volumes of the heart, lung and thoracic cavity, incidence of right ventricular hypertrophy and ascites, and related physiological parameters were followed in the day-old chickens hatched from the above eggs. Lung and heart weights as a percentage of body weight, lung and heart volumes relative to the volume of the thoracic cavity after removing the heart and lungs were higher in chickens hatched at high altitude. Additionally, embryonic triiodothyronine (T3) and thyroxine (T4) levels relative to cardiopulmonary parameters were higher in day-old chickens that hatched at high altitude as compared with chickens hatched at low altitude. This was associated with a lower incidence of right ventricular hypertrophy and ascites in chickens hatched at high altitude. Our data indicate that chronic hypoxia interacting with the endogenous functions of embryos during embryonic development at high altitude, as adaptation mechanisms, changed the developmental trajectories of cardiopulmonary parameters in postnatal chickens. This important development facilitates an increase in the gas exchange area in broiler chickens, thus lowering their susceptibility to pulmonary hypertension and ascites.

Generation of hydroxyl radicals during ascites experimentally induced in broilers

Increased metabolic rates, pulmonary hypertension and cardiac dysfunction are the most important features of the ascites syndrome in broiler chickens. However, the mechanism of cell injury causing the pathogenesis of the syndrome is not clearly understood. Our study aimed to examine the generation of hydroxyl radicals (OH*) in broiler chickens experiencing ascites. The hundred and fifty 1-d-old chickens were purchased from a local hatchery and reared in an open poultry house for 46 d. They were divided at random into three groups and ascites was induced in two groups by exposing them to low temperature or administration of triiodothyronine (T(3)). The third group served as control and was reared normally. Haematological, biochemical and pathological tests were used to determine the incidence of ascites: including total red blood cell (RBC), packed cell volume (PCV), release of alanine transaminase (ALT) and aspartate transaminase (AST) and ratio of right ventricular weight to total ventricular weight (RV/TV). A salicylate hydroxylation method was used to examine the generation of hydroxyl radicals (OH*) in treated groups. TWo hydroxylated salicylic acid metabolites, 2,3- and 2,5-dihydroxy benzoic acid (2,3- and 2,5-DHBA), were measured by HPLC to detect the generation of OH*. An ascites syndrome was observed in T(3) and low-temperature treated groups, as shown by necropsy changes and increases in f RBC, PCV, ALT, AST and the ratio of RV/TV. Concentrations of 2,3- and 2,5-DHBA were increased in groups experiencing ascites compared to control group. It is suggested that reactive oxygen species that is OH* ions, may be involved in the pathogenesis of the ascites syndrome in broiler chickens.

Anatomical parameters of cardiopulmonary system in three different lines of chickens: further evidence for involvement in ascites syndrome

The present study was designed to compare the anatomical parameters of the cardiopulmonary system in three different lines of chickens with different susceptibility to ascites syndrome. Eggs from three different genetic lines-commercial broiler and layer lines and one native to Iran--were incubated and hatched, and 1-day-old chicks used. The relative heart and lung weights, the volumes of the heart, lung and thorax cavity, the incidence of ascites, and the related physiological parameters in these chickens were followed. Lung weight as a percentage of body weight, the relative lung and heart volume, and the volumes of the thorax cavity, before and after removing heart and lung tissues, were lower in fast-growing broiler chickens compared with the layer and native chickens. Additionally, most of these parameters (e.g. relative lung weight, lung volume and thorax cavity) were significantly decreased with age in broiler chickens but were increased in layer and native chickens, which was concomitant with the incidence of ascites in broiler chickens. Our data indicate that all cardiopulmonary parameters investigated are extremely unfavourable to broiler chickens and suggest a reduction in gas exchange area in broilers, and therefore higher susceptibility to pulmonary hypertension and ascites.

Effect of chronic hypoxia during embryonic development on physiological functioning and on hatching and post-hatching parameters related to ascites syndrome in broiler chickens

The present study was designed to investigate the effect of different atmospheric pressure on the endogenous functions of broiler chickens during embryonic, hatching and growing periods related to ascites. Eggs from a commercial broiler line were incubated in two similar commercial incubators at high and low altitudes. The effect on embryonic development and physiological functions including hatching parameters, incidence of ascites and growth performance were examined. Embryos incubated at high altitude had higher plasma tri-iodothyronine, thyroxine, corticosteroid and lactic acid levels, and hatched earlier than those incubated at low altitude. Embryonic mortality was higher at high altitude. Chickens that had been incubated at high altitude showed less right ventricular hypertrophy and ascites mortality than those incubated at low altitude. It was concluded that different atmospheric pressure during incubation interacts with the endocrine functions of the embryo and hence affects hatching parameters, thereby influencing ascites susceptibility.

Beneficial effects of alternative lighting schedules on the incidence of ascites and on metabolic parameters of broiler chickens

The beneficial effects of different lighting programmes on the incidence of ascites was investigated in an experiment with 360 three-day-old male broiler chickens. At 3 days of age, chicks were randomly divided over three rooms in a high-altitude farm, 2000 m above sea level. During days 14 to 28 ambient temperature decreased during the night but the minimum temperature did not descend below 15 degrees C. In the first room the continuous lighting schedule (CL, 23L:1D) was maintained and in the second room an intermittent lighting schedule (IL, 1L:3D), repeated six times daily, was imposed from 3 days of age. In the third room, an increasing photoperiod schedule (IP, 4 to 14 days, 6L:18D; 15 to 21 days, 10L:14D; 22 to 28 days, 14L:10D; 29 to 35 days, 18L:6D; 36 to 42 days, 23L:1D) was provided. Mortality associated with right ventricular failure and ascites was numerically lower in birds reared under the IL and IP schedules compared to birds reared under the CL schedule, which can be attributed to the temporary reduction in relative growth and feed intake in IL and IP birds. It was concluded that the beneficial effect of lighting schedules could be due to a reduced metabolic rate as a consequence of the altered growth trajectory, as also reflected in the lower haematocrit and plasma T3 levels of IL and IP birds compared to CL birds.

In vitro and in vivo activity of two Pt(IV) salts against leishmania donovani

The activities of 8 platinum drug complex salts were determined against Leishmania donovani promastigotes. The three most active salts were selected: [PtIVBr6]H2 (pentamidine); [PtIVBr6]H2 (stilbamidine), and [PtIVCl6]H2 (2-piperazinyl(1) ethyl amine), which induced growth-inhibition rates of more than 50% at 24 h of treatment and at the maximum dosage tested. The cytotoxicity assays on the macrophage cell line J-774 showed high cytotoxicity for the salt [PtIVBr6]H2 (stilbamidine) with a percentage of specific 51Cr release of 58.2% at 24 h of incubation and 100 microg/ml. Meanwhile, assays of the other compounds showed practically no cytotoxicity. The salt [PtIVBr6]H2 (pentamidine) notably inhibited the incorporation of 3H-thymidine in the treated parasites. The ultrastructural alterations observed in the flagellates treated with the salts [PtIVCl6]H2 (2-piperazinyl(1)ethyl amine) and [PtIVBr6]H2 (pentamidine) suggest that both act preferentially at the nuclear level and at the kinetoplast-mitochondrion complex. Both compounds showed a high in vivo activity in parasitized Wistar rats.