Maintenance Energy Requirements of Double-Muscled Belgian Blue Beef Cows.

Sixty non-pregnant, non-lactating double-muscled Belgian Blue (DMBB) cows were used to estimate the energy required to maintain body weight (BW). They were fed one of three energy levels for 112 or 140 days, corresponding to approximately 100%, 80% or 70% of their total energy requirements. The relationship between daily energy intake and BW and daily BW change was developed using regression analysis. Maintenance energy requirements were estimated from the regression equation by setting BW gain to zero. Metabolizable and net energy for maintenance amounted to 0.569 ± 0.001 and 0.332 ± 0.001 MJ per kg BW(0.75)/d, respectively. Maintenance energy requirements were not dependent on energy level (p > 0.10). Parity affected maintenance energy requirements (p < 0.001), although the small numerical differences between parities may hardly be nutritionally relevant. Maintenance energy requirements of DMBB beef cows were close to the mean energy requirements of other beef genotypes reported in the literature.

Double Muscling in Cattle: Genes, Husbandry, Carcasses and Meat.

Molecular biology has enabled the identification of the mechanisms whereby inactive myostatin increases skeletal muscle growth in double-muscled (DM) animals. Myostatin is a secreted growth differentiation factor belonging to the transforming growth factor-ß superfamily. Mutations make the myostatin gene inactive, resulting in muscle hypertrophy. The relationship between the different characteristics of DM cattle are defined with possible consequences for livestock husbandry. The extremely high carcass yield of DM animals coincides with a reduction in the size of most vital organs. As a consequence, DM animals may be more susceptible to respiratory disease, urolithiasis, lameness, nutritional stress, heat stress and dystocia, resulting in a lower robustness. Their feed intake capacity is reduced, necessitating a diet with a greater nutrient density. The modified myofiber type is responsible for a lower capillary density, and it induces a more glycolytic metabolism. There are associated changes for the living animal and post-mortem metabolism alterations, requiring appropriate slaughter conditions to maintain a high meat quality. Intramuscular fat content is low, and it is characterized by more unsaturated fatty acids, providing healthier meat for the consumer. It may not always be easy to find a balance between the different disciplines underlying the livestock husbandry of DM animals to realize a good performance and health and meat quality.

Effect of daily concentrate intake at weaning on performance of Belgian Blue double-muscled rearing calves.

Weaning at a different daily concentrate intake was investigated during a 140-d experimental period, using 54 male and 68 female newborn Belgian Blue double-muscled animals. They were divided into three comparable groups and received milk at 10% of their birth weight up to weaning. Concentrate was levelled off at a maximum daily intake of 3 kg, while grass hay was freely available. Weaning occurred at a daily concentrate intake level (CL) of 0.5, 0.75 and 1.0 kg, respectively. Weaning at an increased CL prolonged the milk-feeding period by 13.1 and 14.6 days, and resulted in a higher pre- and post-weaning growth rate (p < 0.05). Daily gain during the entire experimental period averaged 0.84, 0.85 and 0.88 kg for the respective groups (p = 0.065). Daily concentrate intake was not different among groups, with only a small effect of CL on intake around weaning. Early weaning resulted in a significant reduction of hay intake (p = 0.032). Total daily net energy intake increased slightly with a higher CL at weaning, so that energy conversion was slightly improved, amounting to 17.7, 17.6 and 17.4 MJ/kg gain, respectively. Energy balance during the first week after weaning was negative for CL 0.5 kg (-22%), while it was close to 0 for CL 0.75 kg (-2%) or positive for CL 1.0 kg. Most effects of CL at weaning were similar for males and females, but male calves tended to have a higher intake and a faster growth rate than females. It can be concluded that weaning should be delayed until Belgian Blue double-muscled calves consume at least 0.75 kg per day or more for reasons of welfare, although performance was hardly improved by weaning at a daily concentrate intake of more than 0.5 kg per day.