Growth and Protein Turnover in the Skeletal Muscles of Broiler Chicks

Abstract

Growth and protein turnover were examined in the breast (pectoralis thoracica) and the leg (gastrocnemius-peroneus) muscles of broiler chicks at 1, 2, 4, and 6 weeks posthatching. The fractional rate of protein synthesis (ks) was measured by an isotope emulsion method. The fractional degradation rate (kd) was calculated from the difference in ks and fractional deposition rate (kg), which was estimated from regression equations of muscle size and protein content on body weights. The growth rate (%/day) of skeletal muscle exceeded that of the whole body. Muscle growth involved an increase in the total deoxyribonucleic acid (DNA) and the DNA-unit size and a subsequent decrease in the concentrations of nucleic acids without alteration in the ribonucleic acid (RNA):DNA ratio and RNA and DNA activity. The ks in breast muscle protein fell markedly from 48 to 16%/day between 1 and 6 weeks posthatching, whereas in leg muscle, ks underwent a more gradual decrease; from 36 to 17%/day during the same period. These changes resulted mainly from the reduction of DNA and RNA concentrations with age. The kd decreased only slightly between 1 and 2 weeks in the both muscle groups. The kg also showed a developmental fall from 33 to 4%/day and from 21 to 4%/day in the breast and leg muscles, respectively, during the 5-week period.(ABSTRACT TRUNCATED AT 250 WORDS)

The IGF-1/Akt/S6 Signaling Pathway is Age-Dependently Downregulated in the Chicken Breast Muscle

“…Previous studies have shown that the fractional rate of protein synthesis decreases with age in skeletal muscle in both mammals (Davis et al, 1989(Davis et al, , 2009) and chickens (Kang et al, 1985;Maeda et al, 1984;Tesseraud et al, 1996). For example, Kang et al (1985) reported that the fractional synthesis rate in the breast muscle decreased by more than 50% between 1-and 2-week old chickens, and then continued to slowly decrease.…”

“…Although the important selection traits change according to production and market trends, growth rate has consistently been the prime selection trait because of its large impact on total meat production cost (Arthur and Albers, 2003). However, growth rate was reported to decrease with age in chickens (Kang et al, 1985;Reiprich et al, 1995), suggesting that the regulation of protein turnover changes with age in chicken skeletal muscle. For example, fractional rates of protein synthesis have been shown to decrease in chicken breast muscle during the period of 1-4 weeks of age, but the fractional protein degradation rate changed little to none during the same period (Kang et al, 1985;Tesseraud et al, 1996).…”

“…However, growth rate was reported to decrease with age in chickens (Kang et al, 1985;Reiprich et al, 1995), suggesting that the regulation of protein turnover changes with age in chicken skeletal muscle. For example, fractional rates of protein synthesis have been shown to decrease in chicken breast muscle during the period of 1-4 weeks of age, but the fractional protein degradation rate changed little to none during the same period (Kang et al, 1985;Tesseraud et al, 1996). These findings suggest that the protein synthetic system is age-dependently downregulated, whereas the proteolytic system changes little with age.…”

Impacto da nutrição pós-eclosão sobre o desenvolvimento de frangos de corte

“…Desta forma, o peso relativo do músculo esquelé-tico, mais precisamente o peitoral, dobra nos cinco primeiros dias após a eclosão . O ganho de peso do músculo peitoral e das pernas com uma semana de idade, representa 6% e 2% do peso vivo da ave, respectivamente KANG;SUNDE;SWICK, 1985).…”

“…Desta forma, o peso relativo do músculo esquelé-tico, mais precisamente o peitoral, dobra nos cinco primeiros dias após a eclosão . O ganho de peso do músculo peitoral e das pernas com uma semana de idade, representa 6% e 2% do peso vivo da ave, respectivamente KANG;SUNDE;SWICK, 1985).A formação da fibra muscular esquelética é finalizada ao nascimento/eclosão nos mamí-feros/aves sendo que depois deste momento, em condições normais, não é possível a realização de mitose das miofibrilas. Entretanto, um grande aumento no conteúdo de DNA muscular, é observado durante o crescimento pós-eclosão das aves, sendo este processo essencial para a hipertrofia muscular.…”