Comparison of Bone and Muscle Growth in Turkey Lines Selected for Increased Body Weight and Increased Shank Width

Abstract

A subline (FL) of a long-term growth-selected line (F) of turkeys was established by mass selecting solely for increased shank width at the narrowest point (dew claw). A comparison was made of bone and muscle growth in Line FL (fourth generation of selection), Line F (17th generation of selection), and a randombred control (RBC2, the base population of F) at 8, 16, and 20 wk of age. Also, a sample of the tibiotarsal and femur bones was studied histologically for evidence of pathological conditions. No significant pathological changes were observed in bones from turkeys of the different lines at the ages examined. Samples for histological study were taken at Day 1, 27, 56, 84, 112, and 140 posthatching. Genetic increases in body weight (F and FL lines) resulted in a significant decline in the relative amount of leg muscles from 16 to 20 wk of age while in Line RBC2 the relative amount of leg muscles increased slightly from 16 to 20 wk of age. This resulted in a significant line × age interaction. No significant differences in the amount of leg muscles were detected between turkeys of Lines F and FL. Amount of breast muscles increased consistently with age in all lines. Amount of breast muscles (absolute and as a percentage of body weight) was larger in Line F than in the FL and RBC2 lines. The actual weight of the breast muscles was larger in Line FL than in the RBC2 line but as a percentage of body weight there was no significant difference. Selection for increased shank width did not increase the weights of the tibiotarsal and femur bones. Curvature of the tibiotarsal bones from individuals of the F and FL lines did not differ significantly, but both had more curvature than individuals of the RBC2 line. Relative leg bone weight increased from 8 to 16 wk of age and then declined by 20 wk of age in all lines. The magnitude of the decline from 16 to 20 wk of age was greater in the large-bodied lines (F and FL) than in the smaller-bodied RBC2 line.