Effects of a bacterial inoculant and propionic acid on preservation of high-moisture ear corn, and on rumen fermentation, digestion and growth performance of beef cattle

Studies of aerobic stability, digestion and growth performance were conduct ed with steers to determine the mode of action of a bacterial inoculant in altering the feeding value of ensiled high-moisture ear corn (HMEC); a comp arison was made with propionic acid (PA) treated HMEC (10 g kg(-1) fresh ma tter). The inoculant consisted of Lactobacillus plantarum and Enterococcus faecium, and was applied as an aqueous solution to provide 10(4) colony-for ming units (cfu) per gram of HMEC. Inoculation of HMEC was not as effective as PA in improving aerobic stability, as assessed by changes in population s of yeasts and moulds. However, steers fed inoculated HMEC gained 11% more weight (P < 0.05) than animals fed untreated HMEC, and 9% more (P < 0.10) than those fed PA-treated material. There were no effects of treatment on f ood intake or digestion of organic matter (OM). At 4 h after feeding, rumen pH and molar proportions of isovalerate were greater (P < 0.05) with inocu lated than untreated or PA-treated HMEC. Treatment differences in aerobic s tability of HMEC did not account for the responses in growth performance. I t appears that improvements in growth rate of beef cattle fed inoculated HM EC may be related to pH and/or the production of iso-acids in the rumen.