WS Influence of supplement type and monensin addition on utilization of low-quality, cool-season forage by beef cattle

Abstract Text: Two studies were conducted to evaluate the influence of supplement composition and monensin addition on intake and digestibility of a low-quality (4.5% CP), cool-season forage, as well as cow performance.  Treatments included a non-supplemented control (CON), approximately 30% CP supplements consisting of corn and urea (CU), CU + monensin (200 mg/day; CU+M), dried distiller’s grains (DDGS), or DDGS + monensin (200 mg/day; DDGS+M).  In Experiment 1, 5 steers were used in an incomplete 5 x 4 Latin square with four 28-d periods to compare the effects of monensin and supplement type on forage intake, digestibility and ruminal fermentation characteristics.  Forage intake tended to be greater with supplementation (P = 0.06), was greater with DDGS compared with CU (P = 0.03), and was decreased with monensin addition (P = 0.04).  Ruminal pH was increased with monensin; however, it was increased more with monensin addition to the DDGS supplement compared with the CU supplement (P < 0.01).  In Experiment 2, 80 late gestation cows were stratified by age, BCS, and BW and randomly allotted to treatments (20 pens; 4 cows/pen; 4 pens/treatment).  Pre-calving and post-calving body condition score (BCS) change were more positive with supplementation (P < 0.01), while monensin addition to the supplements benefited pre-calving (P = 0.02) and post-calving (P = 0.02) BCS change a greater amount with the CU supplement compared with the DDGS supplement.  Monensin addition, irrespective of supplement type, reduced forage intake while maintaining performance of beef cattle consuming low-quality forage.

Keywords: cattle, cool-season, forage, ionophore, monensin, supplementation