Cardiovascular parameters in capitive blue-fronted amazon parrots (Amazona aestiva, Linnaeus, 1758) with varying body condition scores

This study aims at determining the echocardiographic, radiographic and tomographic parameters of blue-fronted Amazon parrots (Amazona aestiva) with varying body condition scores. Thirty-five birds grown in captivity were included in the study and allocated into groups according to their respective body condition scores: Lean, Ideal and Obese. The echocardiographic evaluation revealed that obese parrots presented lower right ventricle dimensions in diastole than lean parrots. The fractional shortening was considerably lower in obese parrots than in parrots with lean and ideal body condition scores, but without statistical significance. The flow rate and the aortic pressure gradient were lower in the lean group than in the ideal group. No differences were observed between the groups when comparing the radiographic and tomographic measurements. Therefore, as is the case in mammals, we can conclude that alterations in the nutritional state of blue-fronted amazon parrots lead to cardiovascular dysfunctions detected only through an echocardiographic evaluation, which represents an important diagnostic tool for these animals. Computed tomography scans allowed a better identification of the structures of the cardiovascular system without the overlaying structures of the celomatic cavity observed in radiographic images. However, radiographic examinations should still be considered the standard screening examination to identify cardiac alterations such as increased or reduced organ dimensions. Standardizing the technique and describing the measurements obtained in this study may serve as a basis for further research.


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The radiographic examination was conducted using a direct digital radiography device 149 (DR-F; GE Health Care Unit, Brazil), with the settings configured at 45 kV, 200mA and 5 mA 150 with 250ms, broad focus, focal-film distance of 100 cm and collimation on the focal region for 151 all projections. Image acquisition was conducted in the following projections: right lateral, with 152 the wings overlaid and extended dorsally, and the legs extended caudally with the femoral heads 153 overlaid; ventrodorsal, with the wings extended laterally and the legs extended caudally 154 symmetrically. The images were analyzed with the PACS system (Synapse, Fuji Medical 155 System, Tokyo, Japan).

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The following measurements were evaluated in the radiography and CT scan: length 157 of the heart (mm), from the base to the apex (lateral projection for radiography and sagittal 158 section for the CT scan) (Fig 3A and 4A, respectively); width of the heart (mm) at the broadest 159 part of the heart (ventrodorsal projection for radiography and dorsal section for the CT scan) 160 ( Fig 3B and 4B, respectively); width of the coelom (mm), from one rib to the other at the same 161 level as the width of the heart for radiography (ventrodorsal projection) ( Fig 3B) and at the 162 largest width of the coelom for the CT scan (dorsal section) ( Fig 4C); ratio between the width 163 of the cardiac silhouette and the width of the coelom (%). 195 shorter diastolic lengths in the right ventricle (6.9 ± 1.6) than lean parrots (9.1 ± 2.1) (p=0.03).

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The radiographic examination showed an overlap of the apex of the heart with the 229 cranial portion of the liver silhouette, which presented a difficulty for taking the measurements 230 of the heart in the lateral projection and made it impossible in the ventrodorsal projection due 231 to a higher degree of overlap. Therefore, the length of the heart in the radiographic images was 232 measured only in the lateral projection. On the other hand, the width of the heart and the width 233 of the coelom were measured in the ventrodorsal projection.
234 No significant differences were observed when comparing the measurements between 235 the groups, both in the radiography and in the tomography. Therefore, the values for all three 236 groups were grouped together and are presented on Table 3.

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In addition to the effects of obesity observed in this study, we also noted that weight 341 loss and malnutrition in parrots also had an impact on the cardiac flow. We observed a reduction 342 in aortic speed and pressure gradient in the Lean group, while the FS was equal or slightly 343 higher than in the Ideal group. In dogs, inducting caloric and protein malnutrition promoted the 344 reduction of the cardiac mass, reduction of the FS and reduction of the cardiac output. The 345 output reduction was attributed to a decrease on the metabolic demands that happened in 346 malnourished individuals [32]. However, there is a lack of studies assessing the influence of 347 nutritional condition over the cardiac function of birds.

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In this study, when the data obtained on the echocardiogram that did not show an 349 influence of the body condition score were grouped (horizontal plane), the values were similar 350 to those observed for psittacidae [17,19] and pigeons [20], except for the length of the left 351 ventricle in systole and diastole, which were lower than the reference values (Table 1). This 352 may be explained by the inconsistent size of the animals and by the different species and 353 subspecies included in the studies.