Grass steer production system to improve carcass and meat quality

摘要

Three different production systems for autumn born dairy steers, managed more or less intensively, have been investigated. The aim of the production systems were to use a basic diet of grass, either grazed or conserved as silage or hay, combined in various proportions. The animals were slaughtered, aiming for the same degree of fattening, but at three ages. The intensive management aimed at slaughter in January-February at 26-28 months of age after indoor finishing with silage or hay. An "intensive out-of-season" management wished improve at slaughter at 28-30 months of age. Finally an extensive management with finishing at grazing resulted in slaughter in May-June at 30-33 months of age. In three successive factorial experiments, 106 steers of twogenotypes, Holstein and Montbeliard were reared to test the effects of the three production systems. The animals were evaluated for productive traits, carcass quality and biochemical characteristics of m. longissimus thoracis and m. rhomboideus thoracis.For both breeds, the "extensive" animals produced heavier carcasses (+20 kg between "intensive" and "extensive"; P<0.002). The carcass conformation evaluated by the EUROP classification did not differ between the production systems. The estimated percentage of adipose tissue of the carcass was significantly lower for the "extensive" steers (P<0.05). The shear force measured on raw meat was not significantly affected by the production system, but after cooking, the shear force was higher for the extensive management as was the total collagen content. The haeminic iron content was always lowest in the intensive management. The results of these three series of experiments show that it is possible to produce steers with a feeding regime consisting mainlyof grass (from 87% to 94% of the dry matter intake) grazed or harvested as hay or silage. To make the best use of the herbage resources of the farm and to limit the purchase of concentrates, the production of autumn born steers slaughtered at 32 months seems to be an attractive production system for dairy farmers.