Cardiothoracic ratio and vertebral heart scale in clinically normal black-rumped agoutis (dasyprocta prymnolopha, wagler 1831)

Wild rodents, such as the lowland paca (Cuniculus paca), capybara (Hydrochoerus hydrochaeris), rock cavy (Kerodon rupestris), guinea pig (Cavia aperea), and black-rumped agouti (Dasyprocta prymnolopha) are intensely hunted throughout Amazonia and at the semiarid regions of northeastern Brazil. To contribute to the preservation of these species, more information about their anatomy, physiology and pathophysiology is needed. The aim of this study was to standardize the vertebral heart scale (VHS) and cardiothoracic ratio (CTR) in clinically normal black-rumped agouti, as well as to compare the results of these two methods, which are commonly used to evaluate the cardiac silhouette in domestic animals. Twelve healthy black-rumped agoutis, divided into two groups (six males and six females), obtained from the Nucleus for Wild Animal Studies and Conservation at the Federal University of Piauí, were radiographed in right and left lateral and dorsoventral projections. The values of the VHS were 8.00 ± 0.31v (the number of thoracic vertebral length spanned by each dimension, starting at T4) for males and 8.11 ± 0.41v for females, and there was no statistical difference between the decubitus (right and left) or between males and females (P > 0.05). The CTR mean values obtained were 0.51 ± 0.03 for males, and 0.52 ± 0.02 for females, and there was no statistical difference between the genders (P > 0.05). However, there was positive correlation between VHS and CTR (r = 0.77 right decubitus and r = 0.82 left decubitus). The thoracic and heart diameter had mean values of 6.72 ± 0.61 and 3.48 ± 0.30 cm (males), and for the females, it was 6.61 ± 0.51 and 3.5 ± 0.30 cm, respectively, and there was statistical difference between the genders. The results demonstrated high correlation between the VHS and CTR producing similar results, indicating similar clinical precision for assessing the size of the cardiac silhouette in the black-rumped agoutis.