Effect of cold process monensin enriched urea molasses mineral blocks on performance of crossbred calves fed a wheat straw based diet

Twenty male crossbred calves were divided into four equal groups. Calves in groups I and II were fed wheat straw ad libitum with a concentrate mixture with or without monensin (30 mg per day per animal). Calves in groups III and IV were fed wheat straw ad libitum with 70% of the allocated concentrate mixture and had free access to urea molasses mineral block (UMMB) with or without monensin (100 ppm). Wheat straw intake was higher (P<0.05) in UMMB supplemented groups, but total dry matter (DM) and crude protein (CP) intake did not differ. ME (Mcal per day) intake was higher (P<0.05) in UMMB supplemented groups. Digestibility of DM, OM, EE, and NDF did not differ due to UMMB or monensin supplementation, although ADF digestibility was increased (P<0.01) with UMMB supplementation. Although the N balance was similar among the groups, the Ca and P balances were higher in UMMB supplemented groups. Blood glucose level was increased (P<0.05) due to monensin treatment but plasma urea N level did not differ. Average body weight gain, feed conversion efficiency, protein utilisation efficiency, and energy utilisation efficiency were higher (P>0.05) in monensin treated groups without any change in body composition. Replacing 30% of a concentrate mixture with a cold process UMMB increased the proportional contribution of wheat straw to DM intake but had no effect on animal performance. However, supplementation with monensin increased the blood glucose level, protein and energy deposition, as well as body weight gain and feed efficiency, but with no change in the wheat straw and total DM consumption.