METHANE PRODUCTION IN GOATS GIVEN DIETS BASED ON LUCERNE HAY AND BARLEY

An analysis of data from 102 energy balance trials carried out with Granadina goats, 32 with castrated males and 70 with lactating females, was made with the aim of establishing relationships between methane production and some nutritive attributes of the diet. The diets were based on pelleted lucerne (Medicago sativa) hay and barley and differed widely in the amounts and proportions of their ingredients. Methane production was measured by open-circuit respirometry. The between-animal variation in CH4 production was found to be +/- 8 %. In absolute terms, CH4 production increased on increasing the intake of energy. The CH4 loss was 6.56 or 9.75 kJ/100 kJ of gross energy or digestible energy intake, respectively. The prediction of the CH4 production was best described from knowledge of the amounts of the "in vitro" digestible fractions (g/d) of both the neutral-detergent solubles (DNDS) and the neutral-detergent fibre (DNDF), according to the equation CH4 = 2.24 + 0.0299 DNDS + 0.0889 DNDF. The regression was highly significant and the residual standard deviation +/- 6.63 or +/- 20 % of the mean. It was also found that on increasing the feeding level by one multiple of maintenance there was a reduction in CH4 losses of 1.51 kJ or 2.19 kJ/100 kJ of gross energy or digestible energy intake, respectively. The CH4 production (kJ/100 kJ of gross energy intake) was also related to the apparent digestibility of energy (D, %) determined at the level of nutrition close to maintenance. The equation was CH4 = -2.58 + 0.151 D. The regression was highly significant statistically.