Comparative evaluation of the effects of coconut oil, oilseeds and crystalline fat on methane release, digestion and energy balance in lambs

The effects of coconut oil, crushed whole oilseeds (rapeseed, sun ̄ower seed and linseed) and rumen-protected crystalline fat on methane release, digestion and energy balance in growing lambs were evaluated in relation to an unsupplemented control diet. The diets consisted of maize silage, grass hay and concentrate which was supplemented with the respective lipid source. On average, the ®ve lipid-supplemented diets contained 56 g ether extract per kg dry matter, whereas the unsupplemented control diet had 31 g kgÿ1 dry matter The experiment was carried out with 12 lambs in an incomplete 6 6 Latin square with each lamb being fed, subsequently, three different diets for 3 weeks. Feed was allocated according to calculated requirements of metabolizable protein and energy. Gaseous exchange was measured in open-circuit respiratory chambers. Coconut oil supplementation reduced (p<0.1) methane release per kg live weight by 26% compared to control, and with the use of rapeseed, sun ̄ower seed and linseed the relative reduction was 19%, 27% and 10%, respectively. The effects of the lipid supplementations on methane release were signi®cant when related to gross energy intake (p<0.05), CO2 release (p<0.05) and total energy loss (p<0.01). A persistence of the methane suppression seems to be given at least partially. Supplementing the oilseeds, particularly sun ̄ower seed, reduced (p<0.05) the apparent digestibilities of NDF and ADF. This suggests that the reduced fermentation of ®ber was also important for the methane suppression by oilseeds whereas with coconut oil treatment the direct inhibitory effects on rumen methanogens might have been predominant. Lipid supplementation, except of rumen-protected fat, reduced rumen ̄uid ciliate count (p<0.1) and total VFA concentration (p<0.05), and depressed the concentration of acetate (p<0.05) and butyrate (p<0.001). This diminished (p<0.05) the ratio of acetate to propionate. The apparent digestibilities of individual fatty acids were relatively high in all Animal Feed Science and Technology