Not so fast food Morphological speed limits in the domestic turkey

Meeting Abstract

24-7  Thursday, Jan. 4 11:30 – 11:45  Not so fast food: Morphological speed limits in the domestic turkey STOVER, KK*; BRAINERD, EL; ROBERTS, TJ; Univ. of California, Irvine; Brown University; Brown University

The domestic turkey has been artificially selected for increased muscle mass and rapid growth for meat production, reaching over three times the body mass of a wild turkey. We previously reported that domestic turkeys locomote over six times slower than wild turkeys. This study compares the musculoskeletal components of wild and domestic turkeys to identify what morphological features are contributing to the slow locomotion. We collected 121 CT scans during growth from both turkey strains to assess bone dimensional changes. While the domestic turkey’s hind limb bones did not get much longer, the femur and tibiotarsus had greater polar moments of area, placing bone where it could better resist torsion and bending. We also investigated potential muscle weakness in the hind limb at the tissue level to see if selection for meat quality rather than function has left them compromised. The physiological cross sectional area of the muscle only scaled with body mass0.79, leading to domestic turkeys producing only half as much force per unit body mass (33.9 Nkg-1) as wild turkeys (66.5 Nkg-1). Whole organism morphology changes were investigated by examining differences in muscle proportions between strains. Individual muscles were dissected and weighed. We found that the pectoralis was proportionally larger in the domestic turkey (P=0.0019) contributing to a 26% more anterior center of mass position (P=0.0007). The more anterior CoM in the domestic turkey may lead to other gait changes we observed that were similar to the shuffling gait of Parkinson’s patients, associated with increasing stability. We did not see differences at the tissue level between strains; therefore we conclude that the domestic turkey speed limit appears to result from scaling issues and changes in mass distribution.

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