Long-term effects of ensiled cornstalk diet on methane emission, rumen fermentation, methanogenesis and weight gain in sheep

The objective of this study was to compare the long-term effects of diets rich in either ensiled or dry cornstalk at different concentrate-to-forage ratios on the methane production from sheep. A total of fifty-nine sheep (male, 25.06 ± 0.39 kg live weight at the beginning) were randomly divided into four groups with four diet treatments as follows: ensiled cornstalk diet at 40% (CSH) and 20% (CSL) concentrate level, dry cornstalk diet at 40% (DSH) and 20% (DSL) concentrate level. At different concentrate levels, the sheep fed ensiled cornstalk diet produced a lower methane output (L/d or L/kg DM) than the sheep fed dry cornstalk diet, and the difference was significant when 20% concentrate was added in the diet (P < 0.05). For the rumen fluid analysis, the VFAs concentration showed no difference between four groups, but the acetate: propionate ratio tended to decrease in the ensiled cornstalk-fed sheep in comparison to the dry cornstalk-fed sheep, especially significantly different in stage 1 and 3 (P < 0.05). The methanogen abundance in the ensiled cornstalk-fed sheep was shown to be significantly lower than the dry cornstalk-fed sheep at 20% concentrate level (P < 0.05). During the whole period, the weight gain was not significantly influenced (P > 0.05). This result showed that ensiled cornstalk as roughage added to their diet had the effect of reducing the methane emission from sheep when fed 20% concentrate, and the decrease in acetate: propionate ratio might cause the suppression of methanogenesis by depriving of the hydrogen utilized by methanogens to produce methane.