Patterns of musculoskeletal growth and dimensional changes associated with selection and developmental plasticity in domestic and wild strain turkeys

Abstract

Domestication is a type of experimental evolution in which humans have artificially selected for specific desired traits. Selected strain animals can be utilized to identify correlated responses by comparing them to the wild strain. In particular, domestic turkeys have been selected for increased body mass and high‐growth rate, most significantly over the past 60 years. Yet it remains unclear how artificial selection has affected the morphology and evolution of the musculoskeletal system as a whole. Here, we compare growth rate over 21 weeks, hind limb bone scaling across ontogeny via in vivo CT scanning, and muscle proportions in wild and domestic turkeys to identify differences in structural scaling and the potential contributions of selection and developmental plasticity to whole‐organism morphology. The domestic turkeys grew at a higher rate (0.14 kg/day vs. 0.05 kg/day) and reached over 3 times the body mass of wild birds. Comparing the proportional muscle masses in adult turkeys, only the trunk had a greater mass ratio in the domestic turkey, driven solely by M. pectoralis (2.8 times larger). The proportional increase in only breast meat and no other muscles highlights the surgical precision attainable with artificial selection. The domestic turkey femur and tibiotarsus displayed increases in polar moment of area, apparently maintaining torsional strength as body mass increased. The lack of dimensional change in the more vertically held tarsometatarsus is consistent with the pattern expected due to developmental plasticity. These results from the domestic turkey emphasize that there are morphological limits to preserving the balance between growth and function, and varying rates of trait evolution can further complicate this equilibrium.

Waddle and shuffle: Gait alterations associated with domestication in turkeys

“…Increased body mass is just one of the morphological changes that correlate with waddling; others include wide stance width and altered CoM position. Domestic turkeys have increased body mass, only slightly longer limbs, wider stride width during walking (current study) and muscle mass distribution differences compared with wild turkeys (Stover et al, 2018), as well as a more anterior CoM position (Fig. 6).…”

“…The poultry industry has selected for traits that have decreased the time to market and increased meat production (Yost et al, 2002). The turkey, Meleagris gallopavo Linnaeus 1758, in particular has undergone large changes in muscle morphology and mass, with some broad-breasted white (domestic) strains reaching over 3 times the body mass of wild turkeys (Stover et al, 2018). Selection for breast meat has also resulted in pectoral hypertrophy in the domestic strains (Stover et al, 2018;Velleman et al, 2003), leading to an altered distribution of body mass (Abourachid, 1993;Stover et al, 2018).…”

“…The turkey, Meleagris gallopavo Linnaeus 1758, in particular has undergone large changes in muscle morphology and mass, with some broad-breasted white (domestic) strains reaching over 3 times the body mass of wild turkeys (Stover et al, 2018). Selection for breast meat has also resulted in pectoral hypertrophy in the domestic strains (Stover et al, 2018;Velleman et al, 2003), leading to an altered distribution of body mass (Abourachid, 1993;Stover et al, 2018). All of this extra body mass is supported by hindlimb bones that are only slightly longer than those of wild turkeys (Stover et al, 2018).…”

“…Selection for breast meat has also resulted in pectoral hypertrophy in the domestic strains (Stover et al, 2018;Velleman et al, 2003), leading to an altered distribution of body mass (Abourachid, 1993;Stover et al, 2018). All of this extra body mass is supported by hindlimb bones that are only slightly longer than those of wild turkeys (Stover et al, 2018). Structurally, domestic turkeys are not scaled-up wild turkeys, with selection leading to altered skeletal dimensions and proportionally greater pectoral muscle mass.…”

Increased microbial diversity and decreased prevalence of common pathogens in the gut microbiomes of wild turkeys compared to domestic turkeys

“…In the past ~70 years, intensive selective breeding of turkeys has resulted in dramatic changes in commercially raised birds compared to their wild relatives, leading to a genome that is much less diverse than many other agricultural species (4). These genetic changes as well as advancements in production practices have resulted in domestic birds maturing much more quickly and reaching three times the body mass of wild birds at maturity (6). Domestic turkeys are now the second most important source of poultry in the world, with the USA producing ~250,000,000 turkeys and ~7,000,000,000 pounds of turkey meat in 2019 (7).…”