ENTERIC METHANE EMISSION ESTIMATED WITH THE SF6 TRACER TECHNIQUE IS RELIABLE ON RUMEN CANNULATED SHEEP FED FORAGES SILAGES DIETS

The aim of this work was to study the effect of rumen cannulation on methane emission estimated with the SF6 tracer technique in sheep fed forages silages diets based on mixtures of grass and legumes. Ten castrated male Texel sheep were allocated into 2 homogenous groups of 5 animals in which sheep were equipped with a rumen cannula (C+) or without (C-). Each group was fed ad libitum with five silages diets of pure timothy (T), mixture of T and sainfoin (T-SF, 50/50), T and red clover (T-RC, 50/50), SF-RC (50/50), T-SF-RC (50/25/25) in a 5x5 Latin square design. Dry matter intake (DMI) was recorded daily. Methane emissions using the SF6 technique was performed on 4 successive days. Dry matter intake (DMI, kg/day) was significantly lower for sheep in the group C+ than in the group C- (-11% on average; P < 0.05), and similar among diets within each group. Methane emission (g/day) was significantly lower for sheep in group C+ than in group C- (- 14% on average; P < 0.01), and similar among diets within each group. Methane yield (g/kg DMI) was similar between groups C+ and C-, but differed among diets for both groups (P < 0.01): values were higher (+17% on average) with T diet than with other diets which were similar among them. In our experimental conditions, it can be concluded that enteric methane emission estimated with the SF6 tracer technique was reliable in rumen cannulated sheep. Forages silages diets including legumes (sainfoin and/or red clover) reduced methane yield in sheep compared to a diet of pure timothy grass