Effects of Dietary Types or Concentrate-to-Forage Ratios on Rumen Methane Emissions of Sheep

The objective of this study was to compare the effects of diets rich in either cornstalk silage or dry cornstalk of different concentrate-to-forage ratios on the methane production of sheep over a period of ten months. A total of fifty-nine sheep were randomly divided into four groups and fed to cornstalk silage and dry cornstalk diet at 40% and 20% concentrate level. The methane production was analysed using the sulphur hexafluoride (SF6) tracer gas technique. The ruminal fluid was analysed for pH, VFA and ammonia-N concentrations. Based on the 40% or 20% concentrate proportion, the sheep fed the cornstalk silage exhibited a lower methane production (28.13 vs. 31.97 L/d or 28.41 vs. 33.9 L/d) and lower methane emissions per kg of DMI (33.96 vs. 35.35 g/kg or 35.38 vs. 40.43 g/kg) than the sheep fed the dry cornstalk. Furthermore, the sheep fed the cornstalk silage also displayed lower gross energy losses as methane (8.27 vs. 8.57% or 8.69 vs. 10.42%) than the sheep fed the dry cornstalk. For the rumen fluid analysis, the acetic-to-propionic acid proportion tended to decrease for the sheep fed the cornstalk silage when compared with that of the sheep fed the dry cornstalk. Cornstalk silage added to the diet had the effect of reducing the methane emissions from sheep, but the mitigating effect of the silage was influenced by the concentrate-to-forage ratio, the effect of adding the cornstalk silage was significant when the amount of concentrate was set at a low level.