Collaborative Studies On Cyanosis In Broiler Breeders

Cyanosis refers to a dark bluish or purplish coloration of the skin and mucous membranes. Cyanotic meat-type broiler breeder males have been seen for years in the commercial poultry industry. It has been hypothesized that this condition may be initiated by some underlying cardiovascular defect or dysfunction, which is then exacerbated later in life due to risk factors such as male feeding programs, demand for reproductive performance, and/or environmental stressors.The objective of this research project was to determine the primary cause of cyanosis in adult male broiler breeders.

This project was primarily designed to evaluate the cardiac function of these broiler breeder males. Some preliminary tests had indicated that echocardiography may be helpful in this process. Males of three different breed strains from multiple production companies were evaluated over the course of the project. After echocardiography, the males were necropsied and the hearts collected for further histopathological evaluation. Information gathered included body weights; breast fleshing scores; blood parameters such as cholesterol, hematocrits, nitrates; and heart function analysis of the left side of the heart.

A wide variety of quantitative and subjective as well as gross and microscopic evaluations was performed on hearts obtained from normal roosters and roosters manifesting with transitory skin cyanosis or echocardiogram abnormalities. A number of suggestive but mostly not statistically significant differences were observed between the echocardiogram [echo] normal and echo abnormal groups. A striking breed difference was noted in the occurrence of left ventricular area dilation as reflected in gross measurements for the ratio of ventricle chamber to total ventricle area.

While no hearts in the Breed A group demonstrated a ventricle area ratio above 9%, the Breed B and Breed C groups exhibited an incidence in this parameter of 25% or greater. Conversely, the number of hearts in the Breed A group below a ratio of 4% was much greater than the other breeds. The combined evidence of increased left ventricular wall width and an increase in the incidence of left ventricle ratios below 4% argue for the possible presence of a constrictive form of cardiomyopathy in some birds in this group. It should be emphasized that the clinical or pathological importance [if any] of these breed findings is not known and they may simply reflect breed differences of no major importance. At the microscopic level, no major differences in routine subjective histopathology were observed between the echo abnormal and normal groups; nor were any remarkable microscopic pathology present.