Effect of dietary physical structure on animal performance and lesions in the ruminal wall and feet of Belgian Blue double-muscled bulls

The influence of the physical structure level in the diet on animal performance was investigated in 52 Belgian Blue double-muscled bulls starting from a live weight of 348 kg until slaughter at about 645 kg. Four diets with different concentrate/ maize silage ratios were offered ad libitum. The structural value (SO, developed in Belgium as a measure of physical structure in the diet for dairy cows, amounted to respectively 0.63 (HSV, high SV), 0.54 (MSV, moderate So, 0.43 (LSV; low So and 0.34 (VLSV, very low So per kg dry matter Growth rate, food intake and food conversion were all linearly affected by the decreasing SV of the diet. Among carcass parameters only the SEUROP conformation score showed a significant effect of the SV, with the MSV group having the highest score and VLSV the lowest. No important influence of the SV on the histological damage of the ruminal papillae or on the foot lesions was found. Based on the lower growth rate and food intake of the LSV group versus the HSV group, a SV of the diet between 0.54 and 0.43 is considered as an absolute minimum for Belgian Blue double-muscled bulls.