Grass valorisation and muscular characteristics of blonde d'Aquitaine steers

The blonde d'Aquitaine breed, the males of which are traditionally raised as young steers in intensive systems, is spreading beyond its region of origin. In pasture regions these males could be introduced into more extensive grazing systems. The purpose of this study is to assess the capa- bility of these animals to valorise forage resources and also the characteristics of the carcasses pro- duced and of the muscles concerned when considering meat tenderness. The study used young weaned bulls reared as beef animals and slaughtered at 33 months of age ( n = 22 and 24). These beef animals use 2 very different types of pasture during the pasturing seasons (April-November). During the first winter period of rearing the Blonde d'Aquitaine show a lower ingestion of forage (5.8 kg dry matter.100 kg -1 life weight vs. 7.5 kg dry matter.100 kg -1 life weight) and lower growth than the Charolais (1 150 g.d -1 vs. 1 400 g.d -1 ). At pasture, the activity of the animals is similar (380 minutes at pasture, 52 bites per minute for speed of ingestion). At slaughter, at the same body weight (695 kg), the Blonde d'Aquitaine have a greater weight of muscle (+ 9%, 335 kg of muscle vs. 308 kg). The Blonde d'Aquitaine have a more glycolytic muscular metabolism (1 497 μmol. min -1.g -1 vs. 1351 μmol.min -1.g -1 ), a higher proportion of fast, IIB fibers (63.6% vs. 58.8%) and less collagen (3.7 μg d'OH-prol.mg -1 of DM vs. 5.2 μg d'OH-prol.mg -1 of DM). These results show that animals of blonde d'Aquitaine breed provide a good valorisation of forage and grass and that under these breeding conditions, they produce muscles with favourable characteristics for production of tender meat. blonde d'Aquitaine / Charolais / grass / muscle fibers / collagen