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, sunflower 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 five lipid-supplemented diets contained 56 g ether extract per kg dry matter, whereas the unsupplemented control diet had 31 g kg(-1) dry matter The experiment was carried out with 12 lambs in an incomplete 6 x 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, sunflower seed and linseed the relative reduction was 19%, 27% and 10%, respectively. The effects of the lipid supplementations on methane release were significant 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 sunflower seed, reduced (p < 0.05) the apparent digestibilities of NDF and ADE This suggests that the reduced fermentation of fiber 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 fluid 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 groups unless supplied in minute amounts. C-18:0 excretion exceeded intake in all groups presumably due to endogenous excretion or microbial synthesis and, with the oilseeds, possibly also from an enhanced excretion of hydrogenated unsaturated fatty acids of dietary origin. Energy balance remained quite similar with control, crystalline fat and coconut oil, whereas with the oilseeds metabolizability of gross energy and the efficiencies of metabolizable energy utilization tended to be lower. (C) 2000 Elsevier Science B.V. Ail rights reserved.