S. Tesseraud et al., Muscle protein turnover during early development in chickens divergently selected for growth rate, POULTRY SCI, 79(10), 2000, pp. 1465-1471
To explore the mechanisms involved in the genetic control of muscle growth
and protein gain, protein metabolism was assessed in the pectoralis major m
uscle of two chicken lines selected for either fast or slow growth. Protein
synthesis was measured in vivo at various ages from 1 to 4 wk, using a flo
oding dose of L-[4-H-3] phenylalanine. Protein degradation was estimated as
the difference between synthesis and deposition. Over the experimental per
iod, BW were about 2-fold greater (P < 0.001), and pectoralis major muscle
weights were 2.4- to 3.6-fold higher (P < 0.001), in chicks from the fast-g
rowing line (FGL) than those from the slow-growing line (SGL). Independent
of age, absolute rates of protein deposition, syn thesis, and breakdown wer
e higher in FGL than in SGL chickens. Fractional rates of muscle protein sy
nthesis clearly decreased with age. When comparing birds of the same age, f
ractional rates of muscle protein synthesis tended to be lower in the FGL.
Fractional degradation rates (KD) were significantly lower in FGL chickens
during the first 2 wk of post-natal growth, whereas KD were similar between
lines in older chickens. Ln this experimental model of chicken lines diver
gently selected for BW, the greatest line-related difference in muscle prot
ein metabolism was in KD, and was observed in the early growth phases.