Effect of Differences in Forage Quality on Methane Production and Ruminal Fermentation Characteristics of Hanwoo Steers

Abstract

The purpose of this experiment is to determine CH4 production and ruminal characteristics for different quality of forages. Four Hanwoo (Korean native beef cattle)  steers (initial body weight, 374 ± 40 kg) were used in a duplicated 2 × 2 Latin square design and fed either lacerated rice straw (RS) ad libitum plus 3.2kg of concentrate/d or lacerated Italian ryegrass (IRG) silage (dry matter 58.5%) ad libitum plus 3.2kg of concentrate/d. CH4 production was measured using four confinement-type respiration chambers for two consecutive days. Rumen fluid was collected before feeding and after 1.5 and 3 h after feeding.  The average  OM,  CP  and  NDF  intake  for  steers  fed  IRG  was  around  10% (P=0.086), 19% (P = 0.059) and 30% (P=0.038) higher than those for steers fed RS, respectively. There were no statistically differences in CH4 production (g/d) and conversion rate (%) for steers fed IRG and RS even though indirect estimates of apparent OM and NDF digestibility (g/kg DM) of IRG (0.674 and 0.635, respectively) also were higher (P = 0.009) than those of RS (0.614 and 0.557, respectively). However, CH4  production per digested  NDF (g/kg DM) for steers fed rice straw showed higher trend (35 vs 30.5; P =  0.07) compared with those for steers fed IRG. No differences were observed in total VFA and C2/C3 between treatments. Proportions of isobutyrate and isovalerate were higher (P = 0.003 and P = 0.012, respectively) for steers fed IRG than those for RS. We concluded that the laceration of forage by a TMR mixer might reduce the impact of different forage quality on CH4 production. Therefore, further studies are required to establish the role of physical and mechanical properties when comparing the effect of different forage qualities on ruminal methane production.