Effects of extruded linseed on methane emission and milk production of dairy cows

Sammanfattning: The agriculture sector is one of the major sources to produce greenhouse gases of today. One big contributor is methane (CH4) generated during rumen digestion of the feed carbohydrates. One approach to lower CH4 output from the agriculture sector, is to change the diet for the cows. Diets with extruded linseed (EL) have in earlier studies showed to have a lowering effect on CH4 output from cows. Previous studies have shown correlations between CH4 output and fatty acid (FA) profile of milkfat. EL has also shown in previous studies to influence the FA profile in milkfat. The objects of this study were to evaluate if CH4 output can be reduced if diets are supplemented with extruded linseed, if CH4 increases the concentration of unsaturated FA in milk fat, and the effect of EL on milk yield. In this study a total of 177 cows from five herds were individually scanned for CH4 output, milk fatty acid profile and milk yield. Cows were studied while fed a control diet, during the treatment diet with EL and when going back to the control diet again. EL diets had no effect on milk yield but increased the unsaturated FA in the milk. EL also decreased the CH4 output from the cows with 22% from the first control period to the treatment diet, however there was no increase of CH4 output between treatment period and second control period. Conclusion of this master thesis is that Extruded linseed did not affect the milk yield. EL had an effect on milk fat composition. Due to the unreliable measuring method of methane this study could not point out an obvious decrease of CH4 due to EL.