Characterization of growth and development of male British United turkeys.

Body weight and the size of various organs (tibia, pectoral muscle, leg muscle, liver, spleen, and testes) were monitored in growing male turkeys (British United Turkeys) in an effort to characterize their growth pattern. The results were fitted with either a single- or a double-component Gompertz equation, describing single and diphasic growth patterns, respectively, using an iterative nonlinear estimation algorithm. The diphasic model with an early and a late growth component provided a better description of the body weight function than the single-phase model. The start of sexual maturation, evidenced by testicular development, marked the transition age between the early and the late phases of growth. A single-component Gompertz equation was sufficient to describe growth of various individual organs. Growth of bone and liver appeared to follow the early growth component, whereas the path of muscle development appeared to be closer to the later growth component. The results suggest that the diphasic growth behavior of male turkeys is caused by a differential growth rate of various organs, rather than by a periodicity in the overall growth rate.