Beef production models with Charolais and Angus heifers using seminatural grasslands in summer

Only limited knowledge exists on how to raise cattle, when using seminatural grasslands, to produce beef of high carcass quality. The objectives of these factorially designed studies were to determine the effects of indoor feed intensity (low vs. high) and slaughter age (18 vs. 22 months) on performances and carcass qualities of beef heifers, which where raised from weaning until slaughter and grazed seminatural grasslands from May until October. In the first trial, 56 Charolais heifers were used of which 28 heifers were fed only grass/clover silage (low; CL) at ad libitum intake, and another 28 heifers were fed 2.0 kg of grain daily in addition to the silage (high; CH). In the second trial, 28 Angus heifers were fed grass/clover silage at 80% of ad libitum intake (low; AL), whereas another 28 heifers were fed silage at ad libitum intake (high; AH). From weaning until slaughter, AH had higher average daily gains (ADG) than AL (693 vs. 573 g, P = 0.005). Heifers of both breeds had higher carcass weights and fat classes, and, in addition, Charolais heifers had higher conformation classes at 22 months than at 18 months of slaughter age (P < 0.05). In conclusion, indoor feed intensity affected ADG, whereas carcass traits were mostly affected by slaughter age