AbstractsBiology & Animal Science

Several experiments were conducted with birds differing in body weight, conformation and sternal measurements to obtain information on whether it would be possible during short term selection to influence the shape of the sternum and, if so, what influence this would have on the amount and distribution of the breast meat. The first experiment consisted of sixteen matings between three groups of meat production strains and a strain of giant Leghorn. In the progeny from the first experiment birds were selected on the basis of sternal measurements and breast width in various combinations. A total of three generations were obtained and provided data from 316 males and 319 females in five different matings. The data were subjected to an analysis of covariance to obtain information on the significance of differences between the lines of regression in the measurements taken. The results did not support the original hypothesis that an increase in breast width would bring a concurrent decrease in keel length, keel height or keel indentation. However the muscles of the breast showed some divergent development with selection. An increase in keel length produced a relatively greater increase in the pectoralis major than in the pectoralis secundus whereas an increase in breast width increased both muscles equally. Various measurements of growth were observed in one experiment and it was found that all six measurements taken weekly increased linearly. This supports the hypothesis that general growth factors probably have the greatest influence on development. Some of the measurements in the broiler groups were compared to the same measurements in egg production Leghorns. The lines of regression of these measurements were parallel indicating that no difference exists in the body parts measured, between the broiler groups and the egg production Leghorn.