Nitrogen balance and myofibrillar protein turnover in double muscled Belgian Blue bulls in relation to compensatory growth after different periods of restricted feeding

Abstract

Nitrogen balance and myofibrillar protein breakdown were studied in 16 double-muscled Belgian Blue bulls during a low growth period (0.5 kg d−1) (LGP) of 4 mo (L4), 8 mo (L8), or 14 mo (L14) and the subsequent fattening period (rapid growth period, RGP). The control group (CG) was given a conventional fattening diet; the others received a low-energy, low-protein diet during LGP, and the same diet as the CG during RGP. Measurements were made halfway through the LGP, l mo after the beginning of the fattening period, and 1 mo before slaughter. Nitrogen balance was about half of CG (P < 0.001) during LGP, e.g., 50.8, 21.3, 25.8, and 23.8 g d−1, for CG, L4, L8, and L14, respectively. Between LGP and RGP, N balance increased by about 18 g N d−1 above the control in the compensating groups L4, L8 and L14. This was due to the higher digestibility and the higher metabolizability of the nitrogen in the fattening diet. Lower muscle protein accretion during the LGP resulted from decreased synthesis (P < 0.001) and degradation (P < 0.05) compared with the GC. When changing to RGP different evolution patterns were observed in the three formerly restricted groups, e.g. after a short restriction (L4) both synthesis and degradation rose during the RGP but declined towards the end. After a longer restriction (L8 and L14), synthesis and degradation increased and remained high. The magnitude of these increases was inversely proportional to the length of the restriction period. Key words: Belgian Blue bulls, compensatory growth, nitrogen balance, muscle, muscle protein breakdown

Variation of plasma parameters and nitrogen metabolism in finishing Belgian Blue double‐muscled cull females

“…Protein turnover is understood in the present paper as the whole process of continuous degradation and synthesis of body proteins. During the first finishing period, the characteristics of the turnover of the cull females were quite similar to those reported by Van Eenaeme and colleagues (1998). By contrast, during the second period, all the parameters were reduced by about 25%.…”

“…Double‐muscled BB animals, with their extensive muscle development, retain more nitrogen per kg live weight gain than do animals of other breeds with less developed muscle mass. The efficiency of fixation was higher than 14.3% reported by Coffey and colleagues (2000) but rather low when compared with values close to 35% observed by Van Eenaeme and colleagues (1998). This could be partly associated with age effect, i.e.…”

“…A nitrogen retention of 49.4 g/day in the first period and 38.1 g/day in the second period was higher than value of 21 g/day found by Coffey and colleagues (2000) in Tarentaise heifers but lower than what was observed in bulls by Van Eenaeme and colleagues (1998). Double‐muscled BB animals, with their extensive muscle development, retain more nitrogen per kg live weight gain than do animals of other breeds with less developed muscle mass.…”

Food restriction and refeeding in lambs influence muscle antioxidant status

“…The alteration of the growth pattern during compensatory growth is due to significant modifications in both protein synthesis and protein breakdown (Bruce et al, 1991;Van Eenaeme et al, 1998;Hornick et al, 2000). The increase in protein anabolism efficiency during refeeding after food restriction, a highly beneficial adaptation of animals to undernutrition, requires a large amount of energy (Lobley, 2003) and stimulates the mitochondrial redox chain, which is one of the sources of ROS (Aurousseau, 2002;Drö ge, 2002;Griffiths, 2002).…”