Effect of Forage Quality on Methane Production and Ruminal Fermentation Characteristics of Cattle

Abstract

The purpose of two experiments was to determine CH4 production and ruminal characteristics of different quality forages fed to cattle. In experiment 1, four Holstein Friesian steers (initial body weight, 237 ± 31 kg) were used in a duplicated 2 x 2 Latin square design. Cattle were fed either timothy hay (Ti) ad libitum or rice straw hay (RS) ad libitum. The average daily OM, NDF and CP intakes (kg DM) for cattle fed Ti were 105 (P = 0.001), 102 (P = 0.002) and 221% (P = 0.001) higher than for cattle fed RS, respectively. Apparent OM and NDF digestibility were not different significantly between forages. Cattle fed Ti produced 85% more CH4 (g/d) than cattle fed RS (54.6 and 29.5, respectively

P = 0.081). When CH4 was eressed as per kg DMI and OMI, there were no significances between diets, however, cattle fed RS emitted significantly more CH4 than Ti, based on kg digested OMI (dOMI) (P = <0.0001) and digested NDFI (dDNFI) (P = 0.004). Total VFAs of cattle fed two forages were not different, but propionate proportion of VFA was significantly higher (P <.0001) for cattle fed RS, followed by lowered C2/C3 ratio (P = 0.000). Higher NH3-N concentration was observed (P = 0.002) in rumen fluid of cattle fed Ti than RS. In experiment 2, four Hanwoo (Korean native beef cattle) steers (initial body weight, 374 ± 40 kg) were used in a duplicated 2 x 2 Latin square design. Cattle were fed either lacerated RG hay ad libitum plus 3.2 kg of concentrate/d as fed basis or lacerated Italian ryegrass silage (IRG-s) ad libitum plus 3.2 kg of concentrate/d as fed basis. The average daily OM, NDF and CP intakes for cattle fed IRG-s were 10% (P = 0.086), 18% (P = 0.059) and 31% (P = 0.038) higher than for cattle fed RS, respectively. Indirect estimates of apparent OM and NDF digestibility of IRG-s (67.4 and 63.5%, respectively) were higher (P = 0.009) than those of RS (61.4 and 55.7%, respectively). Daily CH4 production and per kg DMI, OMI and dOMI for cattle fed IRG-s were not significantly different compared to cattle fed RS. Methane production per kg dNDFI for cattle fed RS showed higher trend (P = 0.071) than that for cattle fed IRG-s. Acetate proportion of total VFA was significantly higher (P = 0.000) for cattle fed IRG-s, while butyrate proportion was significantly higher (P <.0001) for cattle fed RS. However, there was no differences in total VFA and C2/C3 between treatments. Proportions of isobutyrate and isovalerate were higher (P = 0.003 and P = 0.012, respectively) for cattle fed IRG-s than RS. We concluded that, when there is enough quality difference between forages, high quality forage is expected to have methane mitigation potential in the aspect of dOMI or dNDFI.