Effect of maturity at harvest on in vitro methane production from ensiled grass

Controlling the time of harvest to affect grass maturity for silage was evaluated as a methane (CH₄) mitigation strategy in a batch culture in vitro with ruminal fluid as inoculum and silage from a mixed timothy (Phleum pretense)-meadow fescue (Festuca pratensis) stand. The stand was cut in May (early maturity [EM]; first cutting), June (late maturity [LM]; first cutting), and August (mid-maturity [MM]; third cutting). Disappearance of neutral detergent fiber (NDF) (EM: 0.58; MM: 0.50; LM: 0.45) and ADF (EM: 0.57; MM: 0.49; LM: 0.45) after 48 h was greater for EM compared to MM and LM, with no difference between the latter two. With advancing maturity, total gas (EM: 166.6; MM: 149.7; LM: 119.3 mL), CH₄ production (EM: 21.4; MM: 17.6; LM: 14.8 mL), and methane production per g NDF digested decreased at 48 h (EM: 120; MM: 92; LM: 74 mL/g NDF digested). Ensiling less mature grass resulted in more CH₄ per unit of NDF digested.