Effects of concentrate level on carcass composition, tenderness and growth rate of Angus x NRF and Limousin x NRF bulls

Sammendrag

In total, 56 bulls of Angus x NRF or Limousin x NRF were fed two levels (either 2.5 or 5.0 kg animal(-1) day(-1)) of concentrate from 12 weeks of age to slaughter in a 2x2 factorial design with cross-breed and concentrate level as fixed factors. The concentrate was a mixture with barley, oats, wheat, soyabean and molasses as main components. In addition, the animals had ad libitum access to grass silage. As expected, the bulls fed the high concentrate diet had higher growth rate than bulls fed moderate level of concentrate. Angus x NRF bulls fed the high level of concentrate showed the highest growth rate of the four subgroups and were on average slaughtered at the age of 15 months. Limousin x NRF bulls fed the moderate level of concentrate were the subgroup with the lowest growth rate and needed 20 months to reach the target slaughter weight, which on average was 280 and 340 kg for Angus x NRF and Limousin x NRF, respectively. Although the animals at the high concentrate level had a greater intake of energy day(-1), there was no significant difference in feed conversion calculated as FUm kg(-1) gain between the subgroups. The Limousin cross-breeds had significantly higher relative proportions of muscle in the carcass, but less bone and fat than the Angus crossbreeds. Consequently, the Limousin x NRF bulls achieved better muscularity grading in the EUROP system than the Angus x NRF bulls. Concentrate level yielded different fatness scores in the EUROP system, while breed did not. The correlation between carcass weight and psoas major or longissimus dorsi muscles was stronger for the former muscle. There was a tendency for Angus x NRF bulls fed the moderate concentrate level to have more tender longissimus muscle than the other subgroups, but this difference was not significant.