The effect of replacing brewers' grains with barley tea grounds in total mixed ration silage on feed intake, digestibility and ruminal fermentation in wethers

Four wethers were used in a 4 × 4 Latin square to study the feed intake, apparent digestibility, nitrogen balance and ruminal fermentation characteristics when fed total mixed ration (TMR) silages which included wet barley tea grounds (WBTG). The TMR silages were prepared using compound feed including wet brewers' grains (WBG), corn, oat hay, alfalfa hay, dried beet pulp, salt and vitamin-mineral supplement in a ratio of 30.7:15:8:24:10:12:0.15: 0.15, respectively, on a dry matter (DM) basis. The WBTG and soybean meal mixture (7:3 on DM basis) were substituted for WBG at ratio of 0% (Control), 5% (LTG), 10% (MTG), and 15% (HTG) on DM of TMR. WBTG addition to the TMR silages increased lactic acid concentration, decreased pH, acetic acid and ammonia-N (P < 0.001). Feed intakes and digestibilities for LTG and MTG (except ether extract (EE) digestibility) treatments were not different from the control (P > 0.05). However, EE and neutral detergent fiber (NDF) intake, crude protein, EE and NDF digestibility was lower, but the DM and gross energy digestibility was higher for the HTG treatment compared to control (P < 0.01). With progressive increases in WBTG concentrations, nitrogen intake, fecal nitrogen and retention nitrogen did not differ, but the urinary nitrogen for MTG and HTG treatments were lower than that of the control (P = 0.001). The ruminal total volatile fatty acid concentration and the molar ratios of propionate and butyrate were higher, but the acetate, ratio of acetate to propionate and ammonia-N content were lower for the HTG treatment compared with the control (P < 0.05). Therefore, the possible proportion of replacing WBG with WBTG for TMR silage can be 10% or less of the diet DM.