Effect of sugarcane condensed molasses solubles, sugarcane molasses and monensin on performance and volatile fatty acid production in finishing steers

Abstract

Three experiments were conducted to compare sugarcane condensed molasses solubles (CMS), sugarcane molasses or a CMS—molasses mixture as ingredients in steer finishing diets, and to determine the effect of monensin in combination with CMS on ruminal volatile fatty acid production. In Experiments 1 and 2, 40 yearling steers were fed on a dry basis 0 or 5% CMS, 5% molasses or 5% of a CMS—molasses mixture (50% w/w fresh basis) for 67 and 96 days, respectively. Steers in Experiment 2 were all fed 33 g/metric ton of monensin. Average daily gain and dry feed conversion rate were, respectively, 0.89 kg and 9.61 in Experiment 1, and 1.28 kg and 6.14 in Experiment 2, with no differences among treatments. There were no treatment effects on carcass characteristics. Experiment 3 was a 2 × 2 factorial arrangement with 0 or 33 g monensin/metric ton fed to 40 yearling beef steers, in combination with 0 or 10% CMS (dry basis), for 134 days. In Experiment 3, 10% CMS decreased gain ( P<0.01) from 1.14 to 0.97 kg and increased dry feed/gain ( P<0.05) from 6.89 to 7.89. Feeding 10% CMS produced leaner ( P<0.05) carcasses, while monensin had no effect on carcass characteristics. Steers fed CMS had increased acetic ( P<0.01), butyric ( P<0.05) and isovaleric ( P<0.01) acid concentrations, and decreased propionic ( P<0.01) and valeric ( P<0.01) acid concentrations. Monensin increased ruminal concentration of propionic ( P<0.01) and isovaleric ( P<0.01) acids and decreased butyric ( P<0.05) and valeric ( P<0.01) acids. Condensed molasses solubles may have limited value in replacing molasses or in combination with molasses in finishing diets, and monensin appears to have a beneficial effect when fed in combination with CMS.