Ascites syndrome and related pathologies in feed restricted broilers raised in a hypobaric chamber

The effect of peroxisome proliferator-activated receptor gamma (PPARγ) as a mediator of dietary fatty acids and thiazolidinedione in pulmonary arterial hypertension induced by cold stress of broilers

The objective of this experiment was to evaluate the effects of dietary fish oil and pioglitazone as peroxisome proliferators-activated receptor gamma (PPARγ) activating ligands on the reduction of cold-induced ascites in broiler chickens. A total of 480 one-day-old (Ross 308) male chicks were randomly allocated to four treatment groups with eight replicates of 15 birds each. The following treatments were used: 1) ambient temperature (negative control), with basal diet; 2) cold-induced ascites (positive control), with basal diet; 3) cold-induced ascites, with basal diet +10 mg/kg/day pioglitazone and 4) cold-induced ascites, with basal diet +1% of fish oil. When compared with the positive control, body weight gain was higher (P ≤ 0.05) for broilers fed diets containing fish oil and pioglitazone at 28, 42, and 0-42 d. Broilers under cold-induced ascites had the highest blood pressure at 21 and 42 d, while fish oil and pioglitazone treatment reduced the blood pressure (P ≤ 0.05). Red blood cells, white blood cells, hematocrit, erythrocyte osmotic fragility, bursa of Fabricius and spleen weights were improved (P ≤ 0.05) for chickens fed fish oil diets and pioglitazone compared to the cold-induced ascites (positive control). Exposure to cold temperature resulted in an increase in plasma T3 and T3/T4 ratio and decline in plasma T4 (P ≤ 0.05). In conclusion, PPARγ agonist pioglitazone and fish oil as source of omega-3 polyunsaturated fatty acid could be used as a strategy to reduce the negative effects of pulmonary arterial hypertension and ascites in broiler chickens.

Effect of Qiling Jiaogulan Powder on Pulmonary Fibrosis and Pulmonary Arteriole Remodeling in Low-Temperature-Exposed Broilers

Chinese herbal medicine plays an important role in regulating the nutritional metabolism of poultry and maintaining or improving normal physiological functions and animal health. The present study investigated the effects of dietary supplementation with Qiling Jiaogulan Powder (QLJP) on pulmonary fibrosis and pulmonary arteriole remodeling in low temperature-exposed broilers. Seven-day-old Ross 308 broilers (n = 240) were reared adaptively to 14 days of age. The broilers were randomly divided into six groups: A control group (basal diet and normal feeding temperature); model group (basal diet); low-, medium- and high-dose QLJP groups (basal diet supplemented with 1 g/kg, 2 g/kg, 4 g/kg QLJP); and L-Arg group (basal diet supplemented with 10 g/kg L-arginine). Additionally, all the broilers, except the broilers in the control group, from the age of 14 days old, had a house temperature continuously lowered by 2 °C each day until it reached 12 °C at 21 days of age, and the low temperature was maintained until the end of the experiment. There were four replicates per group and 10 birds per replicate. The results showed that the structure of the lung tissue was clearer and basically intact in the broilers in the QLJP groups, with a small number of collagen fibers formed, and the content of hydroxyproline (HYP) was significantly reduced. QLJP improved pulmonary arteriole lesions, such as tunica media thickening, intimal hyperplasia, arterial wall hypertrophy, and lumen narrowing. QLJP reduced the relative media thickness (%) and relative medial area (%) of the pulmonary arteriole, and significantly decreased the expression level of the alpha-smooth muscle actin (α-SMA) protein in pulmonary arteriole, which alleviated pulmonary arteriole remodeling. The quantitative real-time PCR (qPCR) and enzyme-linked immunosorbent assay (ELISA) results showed that QLJP treatment significantly reduced the gene and protein levels of transforming growth factor-beta l (TGF-β1) and Smad2 in the lung and downregulated the gene and protein levels of collagen type I alpha 1 (COL1A1) and matrix metalloproteinase 2 (MMP2). In conclusion, the results of our study suggested that dietary supplementation with QLJP improved pulmonary fibrosis and pulmonary arteriole remodeling by inhibiting the expression of genes related to the TGF-β1/Smad2 signaling pathway and inhibited the occurrence and development of pulmonary arterial hypertension in low-temperature-exposed broilers.

SNP-based breeding for broiler resistance to ascites and evaluation of correlated production traits

Background

The goal of this study was to evaluate marker-assisted selection (MAS) in broiler chickens using previously mapped gene regions associated with ascites syndrome incidence. The second-generation MAS products were assessed for impact on ascites phenotype and whether there were associated changes in important production traits. Previously, we used whole genome resequencing (WGR) to fine-map 28 chromosomal regions as associated with ascites phenotype in our experimental ascites broiler line (Relaxed, REL) based on a hypobaric chamber challenge. Genotypes for single nucleotide polymorphisms (SNPs) in mapped regions on chromosomes 2 and 22, were used for MAS in our REL line. After two generations, birds homozygous for the genotypes associated with resistance for both chromosomal regions were established. The MAS F2 generation was then compared to the REL line for ascites susceptibility and 25 production traits.

Results

Selection based on SNPs in the carboxypeptidase Q (CPQ, Gga2) and leucine rich repeat transmembrane neuronal 4 (LRRTM4, Gga22) gene regions resulted in a sex- and simulated altitude- dependent reduction of ascites incidence in two F2 cohorts of the MAS line. Comparisons of the F2 MAS and REL lines for production traits when reared at ambient pressure found no significant negative impacts for feed intake (FI), feed conversion ratio (FCR), or deboned part yields for either sex for two F2 cohorts. There were, however, improvements in the MAS for full-trial body weight gain (BWG), FCR, absolute and relative tender weights, and relative drumstick weight.

Conclusions

These results validate the mapping of the 28 chromosomal regions and demonstrate that fine mapping by WGR is an effective strategy for addressing a complex trait; it also stands as the first successful SNP-based selection program against a complex disease trait, such as ascites. The MAS line is comparable and, in some instances, superior, in growth performance to the REL control while being more resistant to ascites. This study indicates that MAS based on WGR can provide significant breeding potential in agricultural systems.

Meta-Analysis and Systematic Review of the Thermal Stress Response: Gallus gallus domesticus Show Low Immune Responses During Heat Stress

Heat stress, which affects broiler growth performance and immunity, is a major concern in the poultry industry. This meta-analysis aimed to demonstrate the significant effect of heat stress on broiler mass gain and immunoglobulin levels, which regulates the mortality rate of broilers. A total of 2,585 studies were downloaded from PubMed, Web of Science, and Google Scholar from January 1, 2015, to September 1, 2021. Eventually, 28 studies were selected based on specific criteria. The results for body mass gain, total mass of immune organs (thymus, spleen, and bursa of Fabricius), immunoglobulin (IgA, IgG, and IgM) levels, and mortality rate were analyzed using odds ratio or the random-effects model (REM) at a confidence interval (CI) of 95%. Compared to the control, heat stress significantly decreased body mass gain (10 trials: REM = 1.35, 95% CI: 1.21, 1.50). Compared to that in the control, heat stress significantly increased immunoglobulin levels: IgA (7 trials: REM = 1.69, 95% CI: 0.90, 3.16), IgG (6 trials: REM = 1.24, 95% CI: 0.85, 1.81), IgM (8 trials: REM = 0.69, 95% CI: 0.44, 1.08), and heat stress also increased the broiler mortality rate (6 trials: REM = 0.06, 95% CI: 0.01, 0.27). However, there were no significant changes in the immune organs between the control and heat-stressed groups. In conclusion, heat stress remarkably alters the mass gain and immunoglobulin levels of broilers, which may be a cause of the high mortality rate.

Genotype-environment interaction in layer chickens in the growing stage: comparison of three genotypes at two different feeding levels with or without red mite (Dermanyssus gallinae) infestation

This study investigated how early growth was affected in various chicken genotypes, which were fed ad libitum or restricted and with or without poultry red mite (PRM) infestation. Atak-S (AS), New Hampshire Red (NHR), and Light Sussex (LS) genotypes were used in the study. In total, 120 chicks were used from each genotype. Four groups were formed: feed-restricted (FR) and infested with parasite (P + ), FR only, fed ad libitum and P + , and fed ad libitum only. Feed restriction was applied as 20 % of the feed consumption of the group fed ad libitum the day before for each genotype. The study was conducted between 2 to 12 weeks of age. Weekly live weights and feed consumption were recorded, and the feed conversion ratio was calculated. Traps were placed in cages to count parasites. Regarding the live weight, NHR tolerated the PRM infestation in the ad libitum feed conditions better than other genotypes. While the infested NHR and AS birds had lower live weights than the non-infested ones under FR conditions, there was no difference between infested and non-infested birds of NHR and AS genotypes when they fed ad libitum. The feed consumption of infested AS and NHR birds was higher than that of non-infested counterparts when fed ad libitum. By contrast, the LS chicks consumed less food in the infested environment. In conclusion, the genotypes responded differently to PRM infestation in different feeding environments.

Identification and validation of quantitative trait loci for ascites syndrome in broiler chickens using whole genome resequencing

BACKGROUND

Ascites syndrome is a hypertensive, multifactorial, multigene trait affecting meat-type chickens imposing significant economic losses on the broiler industry. A region containing the CPQ gene has been previously identified as significantly affecting ascites phenotype. The region was discovered through whole genome resequencing focused on chicken chromosome 2. The association was confirmed through further genotyping in multiple broiler populations.

RESULTS

The whole genome resequencing analyses have now been extended to the current chicken genome assembly. DNA samples were pooled according to gender and phenotype and the pools subjected to next generation sequencing. Loci were identified as clusters of single nucleotide polymorphisms where frequencies of the polymorphisms differed between resistant and susceptible chickens. The chickens are an unselected line descended from a commercial elite broiler line. Regions identified were specific to one or both genders. The data identify a total of 28 regions as potential quantitative trait loci for ascites. The genes from these regions have been associated with hypertensive-related traits in human association studies. One region on chicken chromosome 28 contains the LRRTM4 gene. Additional genotyping for the LRRTM4 region demonstrates an epistatic interaction with the CPQ region for ascites phenotype.

CONCLUSIONS

The 28 regions identified were not previously identified in a multi-generational genome wide association study using 60k Single Nucleotide Polymorphism panels. This work demonstrates the utility of whole genome resequencing as a cost effective, direct, and efficient method for identifying specific gene regions affecting complex traits. The approach is applicable to any organism with a genome assembly and requires no a priori assumptions.

Effects of oxygen levels and a Lactobacillus plantarum strain on mortality and immune response of chickens at high altitude

Chickens reared in high altitude regions suffer from a high mortality, possibly due to poor immune responses induced by hypoxia. This experiment was conducted to evaluate whether increasing the oxygen level or administration of a probiotic could improve mortality and immune response of chickens at high altitude (2,986 m above the sea level). One-d-old chickens were randomly allocated to 1 of 6 treatments in a 2 × 3 factorial arrangement. The first factor was the oxygen level (low and high), while the second factor was the diet (basal diet, basal diet containing aureomycin, and basal diet plus L. plantarum). Increasing the oxygen level significantly reduced the mortality and improved immune responses. The levels of IgA, IgG, IL-10 and anti-BSA antibodies were significantly higher, while IL-1β, LITAF were significantly lower in chickens reared in the high-oxygen room. In the low-oxygen room, L. plantarum significantly decreased the mortality of chickens compared with the other 2 groups. Moreover, L. plantarum significantly increased the levels of IgA, anti-BSA antibodies, IL-10 and decreased IL-1β, LITAF compared with the control group. These results demonstrated that increasing oxygen level or administration of L. plantarum can improve health status of chickens in high altitude regions.

Hippophae rhamnoides as novel phytogenic feed additive for broiler chickens at high altitude cold desert

Extremes of climate and hypobaric hypoxia cause poor growth performance in broiler chickens at high altitude. The present study examined the potential of Hippophae rhamnoides extract as phytogenic feed additive for broilers reared at 3500 m above mean sea level (MSL). Higher content of phytomolecules were recorded during characterization of the extract. Immunomodulatory activity of extract was observed in chicken lymphocytes through in-vitro studies. Thereafter, for in vivo study, 105 day old Rhode Island Red (RIR) Cross-bred chicks were randomly distributed in to control and treatments T1, T2, T3, T4, T5, and T6 which were supplemented with H. rhamnoides aqueous extract along with basal diet, at level of 100, 150, 200, 300, 400, and 800 mg/kg body weight of chicken, respectively. Among the experimental groups, birds in the T3 group represent the highest body weight. Furthermore, treatment group birds had shown better physio-biochemical indices as compared to control group birds. Interestingly, lower mortality rate due to ascites and coccidiosis was recorded in treatment groups and therefore, higher net return was observed. Hence, present investigation demonstrated the beneficial effect of H. rhamnoides extract (@200 mg/kg) at high altitude and therefore, may be used in formulation of feed additive for poultry ration.

Effect of hydro-alcoholic extract of Rhodiola imbricata on growth performance, immunomodulation, antioxidant level and blood biochemical parameters in broiler chickens at high altitude cold desert

Extremes of climate and hypobaric hypoxia cause poor growth performance in broiler chickens at high altitude.The current study was designed to investigate the effect of hydro-alcoholic extract of Rhodiola imbricata onantioxidant, cytokines, blood biochemical and growth performance of broilers at high altitude (3500 m). For invivostudy, one day-old broiler chicks of average initial body weight 36.40±0.42 g were randomly assigned to seven groups in three replicates (10 chicks in each replicate) as per completely randomized design. Experimental groups included control (fed basal diet), and treatment T1, T2, T3, T4, T5, and T6 which received hydro-alcoholic extract of Rhodiola imbricata in drinking water @ 100, 150, 200, 300, 400, and 800 mg/kg body weight of chicken respectively, along with basal diet. Blood samples were collected at 0, 21st, and 42nd day. HPLC analysis of extract revealed the presence of salidroside and p-tyrosol. As a result of this study, birds in T5 group had significantly higher body weight as compared to other groups. Furthermore, they had significantly higher total antioxidant capacity, free radical scavenging activity, interleukin-2, total protein, globulin, HDL level and lower malondialdehyde, interleukin-6, cholesterol, triglyceride, LDL, glucose, A/G, ALT, AST level as compared to control group. Our results suggest that, Rhodiola imbricata extract @ 400 mg/kg body weight of chicken, exhibited beneficial effect on growth performance and therefore, can be used as a phytogenic feed additive for broiler chickens.

Effect of Prunus armeniaca seed extract on health, survivability, antioxidant, blood biochemical and immune status of broiler chickens at high altitude cold desert

Extreme climatic conditions and hypobaric hypoxia at high altitude hinders the growth and productivity of chickens. The present study was carried out to examine the effect of aqueous extract of Prunus armeniaca seeds on health, survivability, antioxidants, plasma biochemical parameters, and immune status of broiler chickens at high altitude. Phytochemical analysis of extract revealed the presence of high phenolics, flavonoids, and carotenoids contents. Before the in vivo study, in vitro efficacy evaluation indicated a significant protective effect of the extract in chicken peripheral blood lymphocytes. For in vivo study, experimental groups include control (fed the basal diet), and treatment T1, T2, T3, T4, T5, and T6 which received an aqueous extract of P. armeniaca in drinking water at concentrations of 100, 150, 200, 300, 400, and 800 mg/kg body weight of chicken respectively, along with basal diet for 42 days. Body weight was significantly increased in all treatment groups as compared to control group and the highest body weight was recorded in T3 group. Higher profit was gained in treatment groups due to lesser mortality in chickens. Moreover, chicken in the treatment groups had significantly higher total antioxidant capacity, free radical scavenging activity, interleukin-2, total protein, albumin, globulin level and lower malondialdehyde, interleukin-6, glucose, cholesterol, triglyceride, ALT and AST level as compared to control group. Results suggest that, P. armeniaca extract at 200 mg/kg body weight of chicken, exhibited the beneficial effect on growth performance and survivability rate of broilers and therefore, could be useful as phytogenic feed additive for broiler chickens at high altitude cold desert.

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.

Studies on the growth performance of different broiler strains at high altitude and evaluation of probiotic effect on their survivability

Identification of appropriate breeds of broilers and development of new feed additives is required for the development of poultry industry at high altitude. Therefore, this experiment was conducted first to identify the suitable broiler strain for this region. One week old chicks (150) from three broiler strains, i.e. Vencobb, RIR cross-bred, and Hubbard were randomly selected and divided equally into three groups. All the chicks were provided the same basal diet. The body weight gain and feed: gain responses were significantly (P < 0.05) improved in RIR cross-bred. Mortality was also observed lower in RIR cross-bred. Thereafter, the second trial was conducted in RIR cross-bred to evaluate the effect of probiotic supplementation (T1@ 9 gm/kg feed, T2@ 18 gm/kg feed) on their performance and mortality. No significant differences (P > 0.05) were observed in weight gain, feed intake, feed: gain, and water intake among the three groups, however, mortality from ascites and coccidiosis was reduced in probiotic treated groups. Hence, our results suggest that RIR cross-bred is suitable for rearing in high altitude regions and probiotic supplementation has no beneficial effects on production performance of broilers at high altitude. However, probiotic supplementation indicated lesser loss due to mortality of birds.

Effects of dietary DL-2-hydroxy-4(methylthio)butanoic acid supplementation on growth performance, indices of ascites syndrome, and antioxidant capacity of broilers reared at low ambient temperature

This study examined the effects of dietary DL-2-hydroxy-4(methylthio)butanoic acid (DL-HMTBA) supplementation on growth performance, antioxidant capacity, and ascites syndrome (AS) in broilers reared at low ambient temperature (LAT) from 7 to 28 days of age. Eight hundred 7-day-old broilers were randomly assigned to two ambient temperatures (LAT and normal ambient temperature [NAT]), four supplemental DL-HMTBA levels (0.17, 0.34, 0.51, and 0.68 %) of the basal diet in a 2 × 4 factorial arrangement (ten replicate pens; ten birds/pen). LAT and NAT indicate temperatures of 12-14 and 24-26 °C in two chambers, respectively, and broilers were reared at these temperatures from 7 to 28 days of age. LAT significantly decreased body weight gain (P < 0.001), serum glutathione (GSH) content (day 14, P = 0.02; day 28, P = 0.045), glutathione peroxidase (GSH-Px) activity, and total antioxidant capacity (T-AOC) at 21 days (P = 0.001, 0.015) and 28 days (P = 0.017, 0.010) and increased feed conversion ratio (FCR) (P < 0.001), serum malondialdehyde (day 21, P = 0.000) and protein carbonyl Level (day 14, P = 0.003; day 21, P = 0.035). As for incidence of AS, there were significant effects of LAT on red blood cell (RBC) count (P < 0.05), hematocrit (HCT) (P < 0.05), and the right to total ventricular weight ratio (RV/TV) at 21 days (P = 0.012) and 28 days (P = 0.046). Supplementation of DL-HMTBA markedly decreased RV/TV at day 28 (P = 0.021), RBC (day 21, P = 0.008), HCT (day 21, P < 0.001), mean cell hemoglobin (day 14, P = 0.035; day 21, P = 0.003), and serum protein carbonyl level (day 21, P = 0.009), while significantly increased serum GSH content (day 14, P = 0.022; day 28, P = 0.001), SOD and GSH-Px activities at 21 days of age (P < 0.001 and P = 0.037). The optimal supplemental DL-HMTBA levels in basal diet of broilers aged from 7 to 28 days under low or normal temperatures were similar, so the authors recommended supplemental of DL-HMTBA level was 0.46 %.

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.

Temporary feed restriction partially protects broilers from necrotic enteritis

The objective of this study was to investigate the effect of feed restriction on the intestinal ecosystem and on the pathogenesis of experimental necrotic enteritis in broiler chicks. To induce subclinical necrotic enteritis, an experimental challenge model using a specific diet formulation, Gumboro vaccination, oral inoculation of broilers with a 10-fold dose of attenuated anticoccidial vaccine and multiple oral inoculations with a specific strain of Clostridium perfringens was adopted. Two hundred and forty 1-day-old Cobb 500 broilers were randomly allocated to four groups: feed restricted, challenged, both feed restricted and challenged, and negative control. At 21, 22, 23 and 24 days of age, the intestines, gizzard and liver were collected from 15 birds in each group and scored for gross lesions. The intestinal digesta was collected for pH and viscosity determination. One caecum from each bird was taken for microbiological analysis. The application of feed restriction in birds challenged with C. perfringens reduced the necrotic enteritis lesion score significantly (P ≤ 0.05) and feed restriction significantly reduced (P ≤ 0.05) pH in the small intestine, the viscosity of the jejunum digesta as well as the C. perfringens counts in the caeca compared with the controls. In conclusion, feed restriction of broilers has a positive effect on the intestinal ecosystem and a significant protective effect against necrotic enteritis in the subclinical experimental model.

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.

Possible role of nitric oxide in the pathogenesis of pulmonary hypertension in broilers: a synopsis

Nitric oxide (NO) produced by vascular endothelial cells is an important determinant of the basal tone of small arteries and arterioles. Impaired endothelial NO production has been implicated in the pathophysiology of pulmonary hypertension in humans. Available data suggest that reduction of endothelial NO synthesis, with evidence of reduced endothelial NO synthase expression in pulmonary arterioles, is associated with increased pulmonary vasomotor tone and vascular remodelling in hypertensive broilers. Supplemental l-arginine, a precursor of NO, has been shown to induce flow-dependent pulmonary vasodilation, to prevent reduced endothelial NO synthase expression and to inhibit vascular remodelling in broilers with pulmonary hypertension. Nevertheless, its effect on pulmonary hypertension syndrome incidence is limited. It appears that impaired production of NO is a secondary rather than a causative factor in the pathogenesis of pulmonary hypertension in broilers.

Effects of Feed Restriction and Realimentation on Digestive and Immune Function in the Leghorn Chick

How regulatory changes of digestive and immune functions of the gut influence each other has not been sufficiently studied. We tested for simultaneous changes in the digestive physiology and mucosal immune function of the guts of White Leghorn cockerel chicks undergoing food restriction and realimentation. Chicks were assigned to 1 of 3 groups: control = fed ad libitum 7 to 17 d of age; restricted = feed restricted d 12 to 17 (at 2 restriction levels: 54 and 34% ad libitum); refed = feed restricted d 7 to 13 and then fed ad libitum d 14 to 17. Refed chicks exhibited 1 d of hyperphagy and an increase in apparent digestive efficiency following restriction (ANOVA, P < 0.001). Total small intestine mass and duodenal maltase activity differed among the groups in the order refed > control > restricted, as expected (ANOVA, P < 0.05 for both measures). In contrast, there were no significant treatment effects on our measures of gut immune structure and function, including bursa mass, spleen mass, and total IgA content of intestinal flush samples measured with standard ELISA techniques. The results of this study indicated that, during feed restriction and realimentation, some features of gut immune function are maintained unchanged in the face of regulatory changes that influence digestive functions.

Effects of early feed restriction and cold temperature on lipid peroxidation, pulmonary vascular remodelling and ascites morbidity in broilers under normal and cold temperature

Two experiments were conducted to evaluate the effects of early feed restriction on lipid peroxidation, pulmonary vascular remodelling and ascites incidence in broilers under normal and low ambient temperature. In experiment 1, the restricted birds were fed 8h per day either from 7 to 14 d or from 7 to 21 d, while the controlled birds were fed ad libitum. In experiment 2, the restricted birds were fed 80 or 60% of the previous 24-h feed consumption of full-fed controls for 7 d from 7 to 14 d. On d 14, half of the birds in each treatment both in experiment 1 and experiment 2 were exposed to low ambient temperature to induce ascites. Body weight and feed conversion ratio were measured weekly. The incidences of ascites and other disease were recorded to determine ascites morbidity and total mortality. Blood samples were taken on d 14, 21, 28, 35 and 42 to measure the plasma malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). On d 42, samples were taken to determine the right/total ventricular weight ratio (RV/TV), vessel wall area/vessel total area ratio (WA/TA) and mean media thickness in pulmonary arterioles (mMTPA). Low-temperature treatment increased plasma MDA concentration. When broilers were exposed to a cool environment for 3 weeks, plasma SOD and GSH-Px activity were decreased compared with normal-temperature chicks. RV/TV, WA/TA and mMTPA on d 42 were increased in birds exposed to cold, consistent with the increased pulmonary hypertension and ascites morbidity. Early feed restriction markedly decreased plasma MDA concentration. The plasma SOD and GSH-Px activity of feed-restricted birds were markedly higher than those fed ad libitum on d 35 and d 42. All early feed restriction treatments reduced ascites morbidity and total mortality. On d 42, the RV/TV, WA/TA and mMTPA of feed-restricted broilers were lower than that of the ad libitum-fed broilers. The results suggested that early feed restriction alleviated the lipid peroxidation, promoted the activity of enzymatic antioxidant and inhibited pulmonary vascular remodelling. These changes might be associated with reduced ascites incidence.

Hypobaric hypoxia in ascites resistant and susceptible broiler genetic lines influences gut morphology

Genetic selection based on rapid growth rates, improved feed conversion, and increased body weights has led to a predisposition to ascites in broiler populations. Sire-family selection was applied to a commercial elite line to produce divergent lines of ascites-resistant (RES) and ascites-susceptible (SUS) broilers by the 8th generation. One objective of this research was to determine the effects of hypobaric hypoxia on gut morphology in these genetic lines. In two separate trials, pedigree broiler chickens were randomly assigned to cages in a hypobaric chamber (simulated 2,900 m above sea level) or a matching local altitude chamber (390 m above sea level). Ascites incidence was characterized by heart enlargement and fluid accumulation in the abdominal cavity. At the end of the study on d 42, all surviving birds were killed and evaluated for the presence of ascites and 2-cm sections from the duodenum and lower ileum were collected from 5 chickens per line, per altitude for each trial for morphometric analysis. At a high altitude, ascites incidence was lower in the RES line (20.9 and 3.7%) than in the SUS line (86.4 and 66.9%, Trials 1 and 2, respectively). No ascites was observed at a local altitude. Under hypoxic conditions, duodenum villus surface area was higher (P < 0.05) in the RES line (181.3 +/- 16.8 and 219 +/- 10.9 microm) compared with the SUS line (130.1 +/- 10.5 and 134.3 +/- 9.3 microm; Trials 1 and 2, respectively). No differences in ileum villus morphology were observed for any of the parameters measured. The reduced surface area in the duodenum of birds selected for ascites susceptibility suggests reduced enteric function and may provide clues as to why these birds have increased incidence of ascites.

Effect of prebiotic on gut development and ascites incidence of broilers reared in a hypoxic environment

Modern broilers have been genetically selected for an increased growth rate and improved feed conversion, but they are also more susceptible to ascites. Ascites occurs when there is an imbalance between available oxygen and the oxygen demand of the broiler. We hypothesized that promoting neonatal gut development with a prebiotic, such as Aspergillus meal (Prebiotic-AM), would enhance gut efficiency, decrease the oxygen demand of the gut, and reduce ascites incidence. In this study, we compared the effect of Prebiotic-AM on ascites incidence and gut development in commercial broilers reared at a local altitude (390 m above sea level) and a simulated high altitude (2,900 m above sea level). Half of the birds received a National Research Council recommended corn-soybean ration, and the other half received the same ration supplemented with 0.2% Prebiotic-AM. These 2 groups were further divided into a local altitude group and a simulated high altitude group for a total of 4 treatment combinations. Tissues were collected on d 1, 3, 7, 14, and 21 from the duodenum and lower ileum and placed in 10% buffered formalin for morphometric analysis. At a simulated high altitude, ascites incidence was 68% for birds fed the Prebiotic-AM supplement compared with 92% ascites incidence in birds given the control feed. The simulated high altitude decreased (P < 0.05) gut development, but prebiotic-treated birds reared in hypoxic conditions had similar gut development to control birds reared at local altitude. These data suggest that a feed ration supplemented with Prebiotic-AM may reduce the effect of hypoxia on broiler gut development and ascites incidence.

Differential expression of cardiac muscle mitochondrial matrix proteins in broilers from ascites-resistant and susceptible lines

Ascites is a metabolic disorder of modern broilers that is distinguished by cardiopulmonary insufficiency in the face of intense oxygen demands of rapidly growing tissues. Broilers with ascites exhibit sustained elevation of pulmonary arterial pressure and right ventricular hypertrophy, the end result of which is heart failure. It has been shown that mitochondrial function is impaired in broilers with ascites. In the current study, mitochondrial matrix protein levels were compared between ascites-resistant line broilers and ascites-susceptible line broilers with and without ascites using two-dimensional (2-D) gel electrophoresis. One hundred seventy-two protein spots were detected on the gels, and 9 of the spots were present at different levels in the 4 groups of broilers. These 9 protein spots were selected for identification by mass spectrometry. Two of the spots were found to contain single mitochondrial matrix proteins. Both mitochondrial matrix proteins, the dihydrolipoamide succinyltransferase component of the 2-oxoglutarate dehydrogenase complex and the alpha-subunit of mitochondrial trifunctional enzyme, were present at higher levels in ascites-resistant line broilers with ascites in the present study. The elevated levels of 2 key proteins in aerobic metabolism in ascites-resistant line broilers with ascites observed in the present study suggests that the mitochondria of broilers with this disease may respond inappropriately to hypoxia.

Differential expression of mitochondrial electron transport chain proteins in cardiac tissues of broilers from pulmonary hypertension syndrome-resistant and -susceptible lines

Pulmonary hypertension syndrome (PHS) is a metabolic disease associated with the rapid growth rate of modern broilers. Broilers susceptible to PHS experience sustained elevation of pulmonary arterial pressure leading to right ventricular hypertrophy and ultimately heart failure. Previous studies have shown that mitochondrial function is defective in broilers with PHS; they use oxygen less efficiently than broilers without PHS. In this study mitochondrial electron transport chain (ETC) protein levels were compared in cardiac tissues from PHS resistant and susceptible line broilers using quantitative immunoblots. Seven of 9 anti-mammalian mitochondrial ETC protein antibodies tested exhibited cross-species reactivity. Six ETC proteins were differentially expressed in the right ventricles of broilers raised under simulated high altitude conditions (2,900 m above sea level). Four ETC proteins were present at higher levels in resistant line birds without PHS than in resistant line birds with PHS or in susceptible line birds with or without PHS. One ETC protein was present at higher levels in broilers without PHS than in broilers with PHS in both lines, and one ETC protein was present at lower levels in susceptible line birds without PHS than in susceptible line birds with PHS or in resistant line birds with or without PHS. Interestingly, differential expression of mitochondrial ETC proteins was not observed in the right ventricles of broilers raised at local altitude (390 m above sea level) nor was it observed in the left ventricles of broilers exposed to simulated high altitude. These results suggest that higher levels of mitochondrial ETC proteins in right ventricle cardiac muscle may be correlated with resistance to PHS in broilers.

Sequence analysis of bone morphogenetic protein receptor type II mRNA from ascitic and nonascitic commercial broilers

Ascites syndrome, also known as pulmonary hypertension syndrome (PHS), is a common metabolic disorder in rapidly growing meat-type chickens. Environmental factors, such as cold, altitude, and diet, play significant roles in development of the disease, but there is also an important genetic component to PHS susceptibility. The human disease familial primary pulmonary hypertension (FPPH) is similar to PHS in broilers both genetically and physiologically. Several recent studies have shown that mutations in the bone morphogenetic protein receptor type II (BMPR2) gene are a cause of FPPH in humans. To determine whether mutations in the chicken BMPR2 gene play a similar role in PHS susceptibility, BMPR-II mRNA from ascitic and nonascitic commercial broilers were sequenced and compared with the published Leghorn chicken BMPR-II mRNA sequence. Fourteen single nucleotide polymorphisms (SNP) were identified in the commercial broiler BMPR-II mRNA. No mutations unique to ascites-susceptible broilers were present in the coding, 5' untranslated or 3' untranslated regions of BMPR-II mRNA. The twelve SNP present within the coding region of BMPR-II mRNA were synonymous substitutions and did not alter the BMPR-II protein sequence. In addition, analysis of BMPR2 gene expression by reverse transcriptase-PCR indicated that there were no differences in BMPR-II mRNA levels in ascitic and nonascitic birds. Therefore, it appears unlikely that mutations in the BMPR2 gene were responsible for susceptibility to PHS in these commercial broilers.

Effect of cold stress on broilers selected for resistance or susceptibility to ascites syndrome

Genetic selection for an ascites-resistant line of broilers is seen as a permanent solution to the ascites problem. Ascites-resistant and ascites-susceptible lines have been developed using sire family selection based on mortality data taken from siblings reared in a hypobaric chamber (simulated 2,900 m above sea level). The relaxed line is representative of the original commercial pureline stock randomly mated with no artificial selection pressure. The objectives of this study were to evaluate the differences between the lines when reared in floor pens and subjected to an ascites-inducing cold stress. Seven hundred eighty three straight run broilers were reared in floor pens at local elevation (390 m above sea level). Feed and water were available ad libitum. Birds were brooded at 32 C during the first week. The second week birds were maintained at 30 degrees C. Cold stress was applied for the remaining 4 wk at 14 degrees C. Mortalities were necropsied daily to determine cause of death. Birds and feed were weighed weekly. At 6 wk, five birds per pen were bled, and half the survivors in each pen (8 to 15 birds) were killed, necropsied, and scored for ascites. Blood gases, clinical chemistries, and blood cell counts were taken. Liver, spleen, split heart, and lung weights were recorded. Body weights were not different among the resistant, susceptible, and relaxed lines (P < 0.05). Feed conversion was better in the resistant line when compared to the susceptible and relaxed lines (P < 0.05). Ascites incidence, as measured by mortality and lesion score at necropsy, was higher in the susceptible and relaxed lines when compared to the resistant line; 18.8, 12.7, and 1.6% respectively (P < 0.001). Susceptible and relaxed lines showed more right ventricular hypertrophy when compared with the resistant line (P < 0.05). The results show that under severe cold stress at local altitude (390 m above sea level), the ascites-resistant line was growing as rapidly as the other lines and was as resistant to ascites as it had been under hypobaric conditions.

Effect of dietary aspirin on ascites in broilers raised in a hypobaric chamber

During the course of ascites development in broilers, many factors can interact to cause hypoxia. To counteract hypoxia, birds with ascites develop greatly increased hematocrit and red cell counts. Increasing hematocrits result in more viscous blood. Prostaglandins are involved in the regulation of constriction and dilation of pulmonary blood vessels and in the formation of blood clots. Dietary aspirin, a prostaglandin inhibitor, was used in an attempt to promote vasodilation and inhibit blood clotting in broilers, with the objective of determining the effect of aspirin on ascites progression. The experimental design consisted of two trials with a total of 1,360, 1-d-old male broiler chicks, which were placed at either local altitude (390 m above sea level) or in a hypobaric chamber that simulated an altitude of 2,900 m above sea level. At each elevation, five dietary treatments were employed: [control, 0.025% crystalline acetylsalicylic acid (aspirin), 0.05% aspirin, 0.10% aspirin, and 0.20% aspirin]. Bird and feed weights were recorded weekly. At the end of 5 wk, blood samples and organ weights were collected, and all birds were examined for signs of ascites. In both trials, birds raised at high altitudes were significantly lighter, had a higher incidence of ascites, and had differences in hematology, compared with birds raised at local elevation. Only in Trial 2, however, did dietary aspirin appear to have any effect on ascites incidence. At the 0.20% aspirin level, a reduction in ascites incidence approached significance compared with controls (34% vs. 56%, P < or = 0.06). Unfortunately, birds fed 0.20% aspirin also were significantly (P < or = 0.01) lighter than controls. Because slowing growth rate is known to reduce ascites, this decrease in BW may have been partially responsible for any beneficial effect on ascites development and progression obtained through feeding aspirin.