Characteristics of Growth and Protein Turnover in Skeletal Muscle of Turkey Poults

Abstract

Protein turnover and DNA and RNA levels were measured in the breast (pectoralis thoracica) and leg (gastrocnemius-peroneus) muscles of large white (Nicholas strain) turkey poults from 1 to 8 weeks of age to investigate their cellular growth and to evaluate the influence of protein turnover on muscle growth. Fractional rates of protein deposition (kg) were determined from regression equations of muscle size and protein content on body weights. Protein synthesis rates (ks) were measured by an isotope emulsion technique. Protein degradation rates (kd) were estimated by the difference between ks and kg.Muscle growth involved increases in total deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), an increase in the DNA-unit size, and decreases in concentrations of the nucleic acids without changes in the RNA:DNA ratio or RNA and DNA activity.The muscles showed developmental changes in ks from 56 to 10%/day and from 38 to 13%/day in breast and leg, respectively, over the 7-week period. The fractional degradation rate also fell from 22 to 7%/day in the breast muscle and from 21 to 10%/day in the leg muscle. The disproportionate decline of ks and kd resulted in an age-associated fall in kg from 34 to 4%/day and from 18 to 3%/day in the breast and the leg muscles, respectively. The efficiency of protein deposition decreased from 61 to 35% in breast muscle and 46 to 20% in leg muscle. The results were qualitatively similar to those obtained in a study with broiler chicks.