Importance of calcium and phosphorus in the diet of double-muscled Belgian blue beef cattle

Double-muscled cattle differ in body composition in comparison with non-double-muscled cattle, which may result in a different mineral content. Therefore, the concentrations of calcium (Ca) and phosphorus (P) in the empty body weight (EBW) of double-muscled Belgian Blue (DMBB) cattle, and the consequence for their requirements were investigated. Forty-nine animals were sacrificed: 8 neonatal calves, 17 growing-finishing bulls with diverging EBW and 24 cows with diverging EBW and body condition. Mean EBW±SE averaged 47±2 kg, 472±32 kg and 625±25 kg, respectively. Concentrations of ash, Ca and P per kg EBW averaged 48, 11 and 7 g, 37, 11 and 7 g, 40, 11 and 7 g/kg for calves, bulls and cows, respectively. Finishing cows (n = 5 out of 24) showed a tendency for lower concentrations of ash and Ca per kg EBW than finishing bulls (n = 5). Concentrations of P per kg EBW were lower in finishing cows than in breeding cows (n = 7), due to a dilution effect as a consequence of a higher fat content in the EBW. Calcium and P contents in the EBW of bulls were very accurately predicted by a linear function (all P 〈 0.001; all R2 〉 0.9) based on BW, but estimates were less accurate in cows, even when BCS and age were used as independent variables. The dietary requirements were calculated using regression equations based on the compositional data and recent information on metabolic losses and absorption coefficients from the literature. From a BW of about 400 kg onwards the accretion of P in growing DMBB bulls is higher than generally assumed. Furthermore, due to a lower feed intake capacity of DMBB cattle compared with non-double-muscled cattle, dietary P concentrations need to be higher than for other breeds. Daily Ca and P requirements for foetal growth are similar to those of non-double-muscled cows.