Comparison of feeding value, ruminal fermentation and bacterial community of a diet comprised of various corn silages or combination with wheat straw in finishing beef cattle

Corn silage is an important feedstuff for cattle because of the joint provision of starch and physical effective fiber and its palatability. However, the whole plant corn silage is underproduced in some regions until today and could not be popularized in beef cattle raising. The objective of this study was to compare the feeding value, ruminal fermentation and bacterial community of a diet comprised of various corn silages or combination with wheat straw in finishing beef cattle. One hundred eighty Simmental crossbred steers were blocked (60 steers/block) on the basis of initial BW. The animals were randomly assigned to 1 of 12 identical research pens (4 pens/block; 15 steers/pen), where each of the 4 research diets was assigned to 1 pen within each block as follows: (1) the whole plant corn silage-based diet was used as the control diet (WPCS), (2) the mixed forages-based diet was formulated by replacing a portion of whole plant corn silage with wheat straw (WPCSW), (3) the corn stalklage-based diet (CS), and (4) the sweet corn stalklage-based diet (SCS). The four diets were formulated to be isonitrogenous and isoenergetic with same forage to concentrate ratio. Experimental diets were fed for 90 d; a diet digestibility trial was conducted at the end of this period. There were no effects (P = 0.596) of treatment on dry matter intake, but average daily gain was greater for steers offered the WPCS diet, intermediate with WPCSW and SCS and lowest with CS (P < 0.001). Dry matter digestibility was greater (P = 0.005) for WPCS and SCS diets than for WPCSW and CS diets. The nutrients digestibility of CS was less than observed for WPCS diet (P < 0.05). The concentrations of ruminal volatile fatty acids were highest for WPCS diet, intermediate with WPCSW diet and lowest with SCS and CS diets (P < 0.001). Diets treatment had no effect on the α-diversity of rumen bacteria in steers (P > 0.05), but only caused the change of relative abundance of Ruminococcaceae and Prevotellaceae (P = 0.036 and 0.037, respectively). In conclusion, the WPCS-based diet exhibited the highest feeding value. The SCS and WPCSW offered suitable alternatives to a WPCS based diet offered to beef cattle, with limited negative influence on growth, apparent digestibility of nutrients and ruminal bacterial microbiota. In contrast, the value of a CS-based diet was relatively poor. However, it may still be economical to substitute WPCS with relative low-quality corn silage in feedlot cattle diets.