Effects of Environmental Temperature on Erythrocyte Numbers and Size

Moye, R. J.; Washburn, K. W.; Huston, Till M.

doi:10.3382/ps.0481683

Cited by 32 publications

(21 citation statements)

References 2 publications

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“…RVF does not usually occur for 2 to 3 weeks but hypoxic conditions in the incubator induce RVF more quickly if chicks are subjected to hypoxic conditions following hatching (Odom et al, 1992a,b;Rosenbaum et al, 1992). Cold also induces polycythaemia (Moye et al, 1969) although it is not clear if it does this by causing hypoxaemia or by reducing plasma volume.…”

Section: Factors Affecting Blood-flow Dynamicsmentioning

confidence: 99%

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Ascites in poultry

1993

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SUMMARYResearch on ascites occurring in meat-type chickens reared at moderate and low altitude has shown that the pathogenesis is similar to that of the high altitude disease. Pulmonary hypertension (PH) caused by increased blood flow or increased resistance to flow in the lung results in right ventricular hypertrophy (RVH), valvular insufficiency, increased venous pressure and ascites. The structure of the avian heart, with its thin-walled right ventricle and muscular right atrioventricular valve, allows PH to induce heart failure quickly. The sudden increase in pulmonary hypertension syndrome (PHS) in meat-type chickens in the 1980s was associated with a rapid increase in growth rate and feed conversion. This was a result of a combination of genetic selection for fast-growing, heavy broilers with low feed conversion and a more dense, high caloric, pelleted food that supplied all the nutrients required for rapid growth and encouraged a high nutrient intake. PHS in meat-type chickens is usually primary pulmonary hypertension, that is, PH that occurs without evidence of prior heart or lung disease that could account for the increase in blood flow or resistance to flow that results in the increased pressure in the pulmonary arteries. The lungs of birds are firm and fixed in the thoracic cavity and they do not expand to draw air into the lung. The blood and air capillaries form a rigid network that allows only minimal expansion of the blood capillaries when more blood flow is required. Air is moved through the lung by abdominal movement which draws air in and out of the air sacs. The anatomy and physiology of the avian respiratory system are important in the susceptibility of meat-type chickens to PHS. The small stature of the modern meat-type chicken, the large, heavy breast mass, the pressure from abdominal contents on air sacs, and the small lung volume compared to body weight, may all be involved in the increased incidence of PHS. There is limited space for blood flow in the avian lung. Factors that increase blood flow or increase resistance to flow are additive. Increased blood viscosity caused by the polycythaemia of hypoxia, or increased erythrocyte rigidity of high Na + , are more likely to produce PH in fast-growing than in slow-growing birds. Increased flow due to cold exposure is also additive. Ascites caused by PH is a production-related disease at low altitude. It can be prevented easily by restricting growth rate. It is possible that some meat-type chickens of the phenotype we have created have reached the limit of blood flow through their lungs and that future improvements in growth rate will only be possible if the lung and abdominal cavity capacities are enlarged.

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Section: Factors Affecting Blood-flow Dynamicsmentioning

confidence: 99%

“…Increased oxygen requirement is probably the most important factor in cold-induced PHS. Cold may also increase blood viscosity (Moye et al, 1969), perhaps by decreasing blood volume.…”

Section: Cold and Heatmentioning

confidence: 99%

Ascites in poultry

1993

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“…The birds that developed ascites as a result of exposure to low temperatures exhibited the same pathological symptoms as those that developed it under low O2 partial pressuresymptoms including increased hematocrit, hemoglobin, heart weight, and rightventricle:total-ventricle ratios [70][71][72]122,124,[143][144][145][146][147].…”

Section: Environmental Causes Of Ascites Syndromementioning

confidence: 99%

Ascites Syndrome in Broiler Chickens - A Physiological Syndrome Affected by Red Blood Cell

Druyan¹

2012

Blood Cell - An Overview of Studies in Hematology

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“…The birds that develop ascites as the result of exposure to low temperatures exhibit the same pathological signs as birds that develop ascites as the result of low oxygen levels, such as, increased hematocrit, hemoglobin, heart wt, and right ventricle:total ventricle ratios (Moye et al, 1969;Julian et al, 1989;Shlosberg et al, 1991Shlosberg et al, , 1992aScheele et al, 1991;Vogelaere et al, 1992;Kranen et al, 1998).…”

Section: Cold Temperaturementioning

confidence: 95%

Ascites Syndrome (Pulmonary Hypertension Syndrome) in Broiler Chickens: Are We Seeing the Light at the End of the Tunnel?

Balog¹

2003

Avian & Poul. Biolog. Rev.

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Ascites syndrome in broilers is a cascade of events that result in cardiac anomalies including an enlarged, flaccid heart, and right ventricular hypertrophy, as well as an accumulation of fluid in the abdominal cavity. Ascites was first noticed as a problem for commercial poultry producers, at farms that were located at high altitudes. Within the last 3 decades, however, ascites has become a significant problem for producers everywhere. Ascites fluid accumulation can be caused by many different factors. There are four general categories of dysfunctions that will result in ascites fluid build-up: (1) vascular damage that allows capillaries to leak; (2) blockage of the lymphatic system that prevents drainage; (3) decreased plasma oncotic pressure; and the most frequently seen dysfunction, (4) increased vascular hydraulic pressure. Increased vascular hydraulic pressure can be caused by several types of pathologies including hepatic, cardiac or right atrioventricular, and the most significant, pulmonary hypertension. Pulmonary hypertension accounts for most cases of ascites seen in commercial broilers, yet the hypertension can originate from many different causes. Environmental causes such as altitude, cold stress and incubator environment will affect the incidence of ascites. Management also plays a significant role in ascites development, for example; feed, lighting, air quality and ventilation have all been implicated in ascites development. Anatomy and physiology of the modern broiler also influences the incidence of ascites. Growth rate, oxygen requirements, organ size and capacity, hematological parameters and cellular responses can all determine how resistant or susceptible a broiler is to ascites. All of these factors cause ascites by inducing hypoxia in the bird (Julian, 1987(Julian, , 1988.The bird's demand for oxygen exceeds its cardiopulmonary capacity resulting in pulmonary hypertension. One final area that not only greatly influences, but also has potential to end ascites syndrome, is the area of genetic selection. In the past, a lot of the blame for our current ascites situation has been placed on poultry breeding and genetic selection for rapid growth, high meat yield and good feed conversion.While genetic selection may have exacerbated the ascites problem, it is also our best solution for eliminating this disorder in the near future.The selection of ascites resistant lines of broilers not only provides birds that can be raised at their maximal growth rate, it also provides a population in which to determine the exact molecular basis for ascites and pulmonary hypertension.

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Effects of Environmental Temperature on Erythrocyte Numbers and Size

Cited by 32 publications

References 2 publications

Ascites in poultry

Ascites in poultry

Ascites Syndrome in Broiler Chickens - A Physiological Syndrome Affected by Red Blood Cell

Ascites Syndrome (Pulmonary Hypertension Syndrome) in Broiler Chickens: Are We Seeing the Light at the End of the Tunnel?

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