Comparative quantitative studies on the microvasculature of the heart of a highly selected meat-type and a wild-type Turkey line

Abstract

In this study the macroscopic and microscopic structure of the heart of a fast growing, meattype Turkey line (British United Turkeys BUT Big 6) and a wild-type Turkey line (Canadian Wild Turkey) were compared. At 8 and 16 weeks of age, 10 birds of each genotype and sex were sampled. The body mass and heart mass of the meat-type Turkey both increased at a faster rate than those of the wild-type Turkey. However in both Turkey lines, the relative heart mass decreased slightly with age, the decrease was statistically significant only in the male Turkeys. Furthermore meat-type Turkeys had a significantly (p < 0.01) lower relative heart mass and relative thickness of the left ventricle compared to the wild-type Turkeys of the same age. The wild-type Turkeys showed no significant change in the size of cardiomyocytes (cross sectional area and diameter) from 8 weeks to 16 weeks. In contrast, the size of cardiomyocytes increased significantly (p < 0.001) with age in the meat-type Turkeys. The number of capillaries in the left ventricular wall increased significantly (p < 0.001) in wildtype Turkeys from 2351 per mm2 at the age of 8 weeks to 2843 per mm2 at 16 weeks. However, in the meat-type Turkeys there were no significant changes, capillary numbers being 2989 per mm2 at age 8 weeks and 2915 per mm2 at age 16 weeks. Correspondingly the area occupied by capillaries in the myocardium increased in wild-type Turkeys from 8.59% at the age of 8 weeks to 9.15% at 16 weeks, whereas in meat-type Turkeys this area decreased from 10.4% at 8 weeks to 9.95% at 16 weeks. Our results indicate a mismatch in development between body mass and heart mass and a compromised cardiac capillary density and architecture in the meat-type Turkeys in comparison to the wild-type Turkeys.