Production, Management and the Environment: Environmental Quality

A total of 3 experiments (Exp), in vitro and in vivo, were conducted to investigate the effects of saponin extracts from Quillaja saponaria (QS), Yucca schidigera (YS) and Camellia sinensis (TS) on CH4 emissions from steers. The in vitro Exp was carried out to determine the effects of saponin inclusion on ruminal methanogenesis and fermentation parameters. Two doses (0.5% and 2.0% of substrate DM) of each saponin were added to the mixture of rumen fluid and buffer for 0, 4, 8, 12 and 24 h incubation. During the in vivo experiments (Exp 1 and 2), concentrations of saponin extracts added to the diets were determined based on the actual saponin content in the extract to provide 0.54 g/kg DM saponin in the diets. Exp 1 used a 3 × 3 Latin Square design with 4 replicates for each treatment, to compare the effects of saponin containing diets, QS (LQS, 1.5% DM) and YS (LYS, 0.64% DM), to a corn and corn silage based control (C1) treatment on enteric CH4 emissions. Exp 2 used a 2 × 2 Latin Square design with 6 replicates to evaluate the effect of TS (LTS, 0.25%) on enteric CH4 emissions, by comparing it to a corn and corn silage based control diet (C2). For each study, 12 Holstein steers were individually housed in environmental rooms for 14 d per period. Methane concentrations were monitored in room exhaust air. In the in vitro experiment, both inclusion rates reduced in vitro CH4 production in all saponin treatments at 24 h incubation (P < 0.01), while gas production and pH were not affected (P > 0.05). Acetate concentration was reduced in all treatments except 0.5% QS and 0.5% YS (P < 0.01). With the exception of the QS 0.5% treatment, all saponin treatments reduced A:P ratio and the NH4-N concentration compared with the control treatment, at 24hr time point (P < 0.01). During both in vivo Exp, feeding saponins to steers did not change ADG or manure excretion characteristics (P > 0.05), but decreased DMI with TS saponin supplementation (P < 0.01). Methane emission mass, emission factors and manure excretions were not affected by dietary saponin inclusion. Results indicated that dietary supplementation of 0.54 g/kg DM saponin did not decrease ruminal CH4 emissions.